-._protesilaos-s-___denote___.-/README.org

#+title: denote: Simple notes with an efficient file-naming scheme
#+author: Protesilaos Stavrou
#+email: info@protesilaos.com
#+language: en
#+options: ':t toc:nil author:t email:t num:t
#+startup: content

#+macro: stable-version 0.1.0
#+macro: release-date 2022-06-27
#+macro: development-version 0.2.0-dev
#+macro: file @@texinfo:@file{@@$1@@texinfo:}@@
#+macro: space @@texinfo:@: @@
#+macro: kbd @@texinfo:@kbd{@@$1@@texinfo:}@@

#+export_file_name: denote.texi

#+texinfo_filename: denote.info
#+texinfo_dir_category: Emacs misc features
#+texinfo_dir_title: Denote: (denote)
#+texinfo_dir_desc: Simple notes with an efficient file-naming scheme
#+texinfo_header: @set MAINTAINERSITE @uref{https://protesilaos.com,maintainer webpage}
#+texinfo_header: @set MAINTAINER Protesilaos Stavrou
#+texinfo_header: @set MAINTAINEREMAIL @email{info@protesilaos.com}
#+texinfo_header: @set MAINTAINERCONTACT @uref{mailto:info@protesilaos.com,contact the maintainer}

#+texinfo: @insertcopying

This manual, written by Protesilaos Stavrou, describes the customization
options for the Emacs package called =denote= (or =denote.el=), and
provides every other piece of information pertinent to it.

The documentation furnished herein corresponds to stable version
{{{stable-version}}}, released on {{{release-date}}}.  Any reference to
a newer feature which does not yet form part of the latest tagged
commit, is explicitly marked as such.

Current development target is {{{development-version}}}.

+ Package name (GNU ELPA): =denote=
+ Official manual: <https://protesilaos.com/emacs/denote>
+ Change log: <https://protesilaos.com/emacs/denote-changelog>
+ Git repo on SourceHut: <https://git.sr.ht/~protesilaos/denote>
  - Mirrors:
    + GitHub: <https://github.com/protesilaos/denote>
    + GitLab: <https://gitlab.com/protesilaos/denote>
+ Mailing list: <https://lists.sr.ht/~protesilaos/denote>

If you are viewing the README.org version of this file, please note that
the GNU ELPA machinery automatically generates an Info manual out of it.

#+toc: headlines 8 insert TOC here, with eight headline levels

* COPYING
:PROPERTIES:
:COPYING: t
:CUSTOM_ID: h:40b18bb2-4dc1-4202-bd0b-6fab535b2a0f
:END:

Copyright (C) 2022  Free Software Foundation, Inc.

#+begin_quote
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with no
Invariant Sections, with the Front-Cover Texts being “A GNU Manual,” and
with the Back-Cover Texts as in (a) below.  A copy of the license is
included in the section entitled “GNU Free Documentation License.”

(a) The FSF’s Back-Cover Text is: “You have the freedom to copy and
modify this GNU manual.”
#+end_quote

* Overview
:PROPERTIES:
:CUSTOM_ID: h:a09b70a2-ae0b-4855-ac14-1dddfc8e3241
:END:

Denote aims to be a simple-to-use, focused-in-scope, and effective
note-taking tool for Emacs.  It is based on the following core design
principles:

+ Predictability :: File names must follow a consistent and descriptive
  naming convention ([[#h:4e9c7512-84dc-4dfb-9fa9-e15d51178e5d][The file-naming scheme]]).  The file name alone
  should offer a clear indication of what the contents are, without
  reference to any other metadatum.  This convention is not specific to
  note-taking, as it is pertinent to any form of file that is part of
  the user's long-term storage ([[#h:532e8e2a-9b7d-41c0-8f4b-3c5cbb7d4dca][Renaming files]]).

+ Composability :: Be a good Emacs citizen, by integrating with other
  packages or built-in functionality instead of re-inventing functions
  such as for filtering or greping.  The author of Denote (Protesilaos,
  aka "Prot") writes ordinary notes in plain text (=.txt=), switching on
  demand to an Org file only when its expanded set of functionality is
  required for the task at hand ([[#h:17896c8c-d97a-4faa-abf6-31df99746ca6][Points of entry]]).

+ Portability :: Notes are plain text and should remain portable.  The
  way Denote writes file names, the front matter it includes in the
  note's header, and the links it establishes must all be adequately
  usable with standard Unix tools.  No need for a database or some
  specialised software.  As Denote develops and this manual is fully
  fleshed out, there will be concrete examples on how to do the
  Denote-equivalent on the command-line.

+ Flexibility :: Do not assume the user's preference for a note-taking
  methodology.  Denote is conceptually similar to the Zettelkasten
  Method, which you can learn more about in this detailed introduction:
  <https://zettelkasten.de/introduction/>.  Notes are atomic (one file
  per note) and have a unique identifier.  However, Denote does not
  enforce a particular methodology for knowledge management, such as a
  restricted vocabulary or mutually exclusive sets of keywords.  Denote
  also does not check if the user writes thematically atomic notes.  It
  is up to the user to apply the requisite rigor and/or creativity in
  pursuit of their preferred workflow ([[#h:6060a7e6-f179-4d42-a9de-a9968aaebecc][Writing metanotes]]).

+ Hackability :: Denote's code base consists of small and reusable
  functions.  They all have documentation strings.  The idea is to make
  it easier for users of varying levels of expertise to understand what
  is going on and make surgical interventions where necessary (e.g. to
  tweak some formatting).  In this manual, we provide concrete examples
  on such user-level configurations ([[#h:4a6d92dd-19eb-4fcc-a7b5-05ce04da3a92][Keep a journal or diary]]).

Now the important part...  "Denote" is the familiar word, though it also
is a play on the "note" concept.  Plus, we can come up with acronyms,
recursive or otherwise, of increasingly dubious utility like:

+ Don't Ever Note Only The Epiphenomenal
+ Denote Everything Neatly; Omit The Excesses

But we'll let you get back to work.  Don't Eschew or Neglect your
Obligations, Tasks, and Engagements.

* The file-naming scheme
:PROPERTIES:
:CUSTOM_ID: h:4e9c7512-84dc-4dfb-9fa9-e15d51178e5d
:END:

#+vindex: denote-directory
Notes are stored as a flat list in the ~denote-directory~ (i.e. no
subdirectories).  The default path is =~/Documents/notes=.

Every note produced by Denote follows this pattern ([[#h:17896c8c-d97a-4faa-abf6-31df99746ca6][Points of entry]]):

: DATE--TITLE__KEYWORDS.EXTENSION

The =DATE= field represents the date in year-month-day format followed
by the capital letter =T= (for "time") and the current time in
hour-minute-second notation.  The presentation is compact:
=20220531T091625=.  The =DATE= serves as the unique identifier of each
note.

The =TITLE= field is the title of the note, as provided by the user.  It
automatically gets downcased and hyphenated.  An entry about "Economics
in the Euro Area" produces an =economics-in-the-euro-area= string for
the =TITLE= of the file name.

#+vindex: denote-allow-multi-word-keywords
The =KEYWORDS= field consists of one or more entries demarcated by an
underscore (the separator is inserted automatically).  Each keyword is a
string provided by the user at the relevant prompt which broadly
describes the contents of the entry.  Keywords that need to be more than
one-word-long must be written with hyphens: any other character, such as
spaces or the plus sign is automatically converted into a hyphen.  So
when =emacs_library= appears in a file name, it is interpreted as two
distinct keywords, whereas =emacs-library= is one keyword.  This is
reflected in how the keywords are recorded in the note ([[#h:13218826-56a5-482a-9b91-5b6de4f14261][Front matter]]).
While Denote supports multi-word keywords by default, the user option
~denote-allow-multi-word-keywords~ can be set to nil to forcibly join
all words into one, meaning that an input of =word1 word2= will be
written as =word1word2=.

#+vindex: denote-file-type
The =EXTENSION= is the file type.  By default, it is =.org= (~org-mode~)
though the user option ~denote-file-type~ provides support for Markdown
with YAML or TOML variants (=.md= which runs ~markdown-mode~) and plain
text (=.txt= via ~text-mode~).  Consult its doc string for the minutia.
While files end in the =.org= extension by default, the Denote code base
does not actually depend on org.el and/or its accoutrements.

Examples:

: 20220610T043241--initial-thoughts-on-the-zettelkasten-method__notetaking.org
: 20220610T062201--define-custom-org-hyperlink-type__denote_emacs_package.md
: 20220610T162327--on-hierarchy-and-taxis__notetaking_philosophy.txt

The different field separators, namely =--= and =__= introduce an
efficient way to anchor searches (such as with Emacs commands like
~isearch~ or from the command-line with ~find~ and related).  A query
for =_word= always matches a keyword, while a regexp in the form of,
say, ="\\([0-9T]+?\\)--\\(.*?\\)_"= captures the date in group =\1= and
the title in =\2= (test any regular expression in the current buffer by
invoking =M-x re-builder=).

[[#h:1a953736-86c2-420b-b566-fb22c97df197][Features of the file-naming scheme for searching or filtering]].

While Denote is an Emacs package, notes should work long-term and not
depend on the functionality of a specific program.  The file-naming
scheme we apply guarantees that a listing is readable in a variety of
contexts.

** Sluggified title and keywords
:PROPERTIES:
:CUSTOM_ID: h:ae8b19a1-7f67-4258-96b3-370a72c43f4e
:END:

Denote has to be highly opinionated about which characters can be used
in file names and the file's front matter in order to enforce its
file-naming scheme.  The private variable ~denote--punctuation-regexp~
holds the relevant value.  In simple terms:

+ What we count as "illegal characters" are converted into hyphens.

+ Input for a file title is hyphenated and downcased.  The original
  value is preserved in the note's contents ([[#h:13218826-56a5-482a-9b91-5b6de4f14261][Front matter]]).

+ Keywords should not have spaces or other delimiters.  If they do, they
  are converted into hyphens.  Keywords are always downcased.

** Features of the file-naming scheme for searching or filtering
:PROPERTIES:
:CUSTOM_ID: h:1a953736-86c2-420b-b566-fb22c97df197
:END:

File names have three fields and two sets of field delimiters between
them:

: DATE--TITLE__KEYWORDS.EXTENSION

The first field delimiter is the double hyphen, while the second is the
double underscore.  These practically serve as anchors for easier
searching.  Consider this example:

: 20220621T062327--introduction-to-denote__denote_emacs.txt

You will notice that there are two matches for the word =denote=: one in
the title field and another in the keywords' field.  Because of the
distinct field delimiters, if we search for =-denote= we only match the
first instance while =_denote= targets the second one.  When sorting
through your notes, this kind of specificity is invaluable---and you get
it for free from the file names alone!

Users can get a lot of value out of this simple arrangement, even if
they have no knowledge of regular expressions.  One thing to consider,
for maximum effect, is to avoid using multi-word keywords as those get
hyphenated like the title and will thus interfere with the above: either
set the user option ~denote-allow-multi-word-keywords~ to nil or simply
insert single words at the relevant prompts.

* Points of entry
:PROPERTIES:
:CUSTOM_ID: h:17896c8c-d97a-4faa-abf6-31df99746ca6
:END:

#+findex: denote
#+findex: denote-type
#+findex: denote-org-capture
#+findex: denote-date
There are four ways to write a note with Denote: invoke the ~denote~,
~denote-type~, ~denote-date~ commands, or leverage the
~org-capture-templates~ by setting up a template which calls the
function ~denote-org-capture~.

In the first case, all that is needed is to run ~denote~.  It will
prompt for a title.  Once it is supplied, the command will ask for
keywords.  The resulting note will have a file name as already explained
([[#h:4e9c7512-84dc-4dfb-9fa9-e15d51178e5d][The file naming scheme]]).

#+vindex: denote-known-keywords
#+vindex: denote-infer-keywords
The keyword prompt supports minibuffer completion.  Available candidates
are those defined in the user option ~denote-known-keywords~.  More
candidates can be inferred from the names of existing notes, by setting
~denote-infer-keywords~ to non-nil (which is the case by default).

#+vindex: denote-sort-keywords
Multiple keywords can be inserted by separating them with a comma (or
whatever the value of the ~crm-indicator~ is---which should be a comma).
When the user option ~denote-sort-keywords~ is non-nil (the default),
keywords are sorted alphabetically (technically, the sorting is done
with ~string-lessp~).

The ~denote~ command can also be called from Lisp, in which case it
expects the =TITLE= and =KEYWORDS= arguments.  The former is a string,
the latter a list of strings.

The ~denote-type~ command is like ~denote~ except it also prompts for a
file type to use as a local value for ~denote-file-type~.  In practical
terms, this lets you produce, say, a note in Markdown even though you
normally write in Org ([[#h:f34b172b-3440-446c-aec1-bf818d0aabfe][Notes in multiple file types]]).

Similarly, the ~denote-date~ command accepts the same =TITLE= and
=KEYWORDS= arguments, though it starts by asking for a date.  Normally,
Denote use the current date and time to construct an identifier, but
~denote-date~ allows the user to specify any date+time combination.  The
input for the =DATE= argument is like =2022-06-16= or =2022-06-16
14:30=.  When the time is omitted, it is interpreted as =00:00=.

Since the ability to insert a date may result in duplicate identifiers,
Denote takes care to abort the operation if such an identity is
established (e.g. when you use ~denote-date~ with =2022-06-16= twice, it
will generate the same identifier of =20220616T000000=).  The user must
thus call the ~denote-date~ command again and provide a unique value.

For integration with ~org-capture~, the user must first add the relevant
template.  Such as:

#+begin_src emacs-lisp
(with-eval-after-load 'org-capture
  (require 'denote-org-capture)
  (add-to-list 'org-capture-templates
               '("n" "New note (with Denote)" plain
                 (file denote-last-path)
                 #'denote-org-capture
                 :no-save t
                 :immediate-finish nil
                 :kill-buffer t
                 :jump-to-captured t)))
#+end_src

[ In the future, we might develop Denote in ways which do not require such
  manual intervention. ]

Once the template is added, it is accessed from the specified key.  If,
for instance, ~org-capture~ is bound to =C-c c=, then the note creation
is initiated with =C-c c n=.  After that, the process is the same as
with invoking ~denote~ directly, namely: a prompt for a title followed
by a prompt for keywords.

#+vindex: denote-org-capture-specifiers
Users may prefer to leverage ~org-capture~ in order to extend file
creation with the specifiers described in the ~org-capture-templates~
documentation (such as to capture the active region and/or create a
hyperlink pointing to the given context).  Due to the particular
file-naming scheme of Denote, such specifiers cannot be written directly
in the template.  Instead, they have to be assigned to the user option
~denote-org-capture-specifiers~, which is interpreted by the function
~denote-org-capture~.  Example with our default value:

#+begin_src emacs-lisp
(setq denote-org-capture-specifiers "%l\n%i\n%?")
#+end_src

Note that ~denote-org-capture~ ignores the ~denote-file-type~: it always
sets the Org file extension for the created note to ensure that the
capture process works as intended, especially for the desired output of
the ~denote-org-capture-specifiers~.

#+findex: denote-create-note
#+findex: denote-create-note-using-type
#+findex: denote-create-note-using-date
For convencience, the ~denote~ command has a ~denote-create-note~ alias.
Same for ~denote-type~ which is ~denote-create-note-using-type~ and
~denote-date~ that has ~denote-create-note-using-date~.  The purpose of
these aliases is to provide alternative, more descriptive names of
select commands to aid with discoverability.

* Renaming files
:PROPERTIES:
:CUSTOM_ID: h:532e8e2a-9b7d-41c0-8f4b-3c5cbb7d4dca
:END:

Denote's file-naming scheme is not specific to notes or text files: it
is useful for all sorts of files, such as multimedia and PDFs that form
part of the user's longer-term storage ([[#h:4e9c7512-84dc-4dfb-9fa9-e15d51178e5d][The file-naming scheme]]).  While
Denote does not manage such files, it already has all the mechanisms to
facilitate the task of renaming them.

#+findex: denote-dired-rename-file
To this end, we provide the ~denote-dired-rename-file~ command.  It has
a two-fold purpose: (i) to change the name of an existing file while
retaining its identifier and (ii) to write a Denote-compliant file name
for an item that was not created by ~denote~ or related commands (such
as an image or PDF).

The ~denote-dired-rename-file~ command will target the file at point if
it finds one in the current Dired buffer.  Otherwise it prompts with
minibuffer completion for a file name.  It then uses the familiar
prompts for a =TITLE= and =KEYWORDS= the same way the ~denote~ command
does ([[#h:17896c8c-d97a-4faa-abf6-31df99746ca6][Points of entry]]).  As a final step, it asks for confirmation
before renaming the file at point, showing a message like:

#+begin_example
Rename sample.pdf to 20220612T052900--my-sample-title__testing.pdf? (y or n)
#+end_example

#+vindex: denote-dired-rename-expert
However, if the user option ~denote-dired-rename-expert~ is non-nil,
conduct the renaming operation outright---no questions asked.

When operating on a file that has no identifier, such as =sample.pdf=,
Denote reads the file properties to retrieve its last modification time.
If the file was from a past date like 2000-11-31 it will get an
identifier starting with =20001131= followed by the time component (per
our file-naming scheme).

The file type extension (e.g. =.pdf=) is read from the underlying file
and is preserved through the renaming process.  Files that have no
extension are simply left without one.

Renaming only occurs relative to the current directory.  Files are not
moved between directories.

#+vindex: denote-dired-post-rename-functions
#+findex: denote-dired-rewrite-front-matter
The final step of the ~denote-dired-rename-file~ command is to call the
special hook ~denote-dired-post-rename-functions~.  Functions added to
that hook must accept three arguments, as explained in its doc string.
For the time being, the only function we define is the one which updates
the underlying note's front matter to match the new file name:
~denote-dired-rewrite-front-matter~.  The function takes care to only
operate on an actual note, instead of arbitrary files.

DEVELOPMENT NOTE: the ~denote-dired-rewrite-front-matter~ needs to be
tested thoroughly.  It rewrites file contents so we have to be sure it
does the right thing.  To avoid any trouble, it always asks for
confirmation before performing the replacement.  This confirmation
ignores ~denote-dired-rename-expert~ for the time being, though we might
want to lift that restriction once everything works as intended.

* Front matter
:PROPERTIES:
:CUSTOM_ID: h:13218826-56a5-482a-9b91-5b6de4f14261
:END:

Notes have their own "front matter".  This is a block of data at the top
of the file, with no empty lines between the entries, which is
automatically generated at the creation of a new note. The front matter
includes the title and keywords (aka "tags" or "filetags", depending on
the file type) which the user specified at the relevant prompt, as well
as the date and unique identifier which are derived automatically.

This is how it looks for Org mode (~denote-file-type~ is nil):

#+begin_src org
:PROPERTIES:
:ID:          20220610T202537
:END:
,#+title:      This is a sample note
,#+date:       2022-06-10
,#+filetags:   denote  testing
#+end_src

Org notes use a =PROPERTIES= drawer at the top of the file for maximum
compatibility with the Org ecosystem, particularly for linking to notes
and exporting them ([[#h:fc913d54-26c8-4c41-be86-999839e8ad31][Linking notes]]).

For Markdown with YAML, the front matter looks like this
(~denote-file-type~ has the =markdown-yaml= value):

#+begin_src md
---
title:      "This is a sample note"
date:       2022-06-10
tags:       denote  testing
identifier: "20220610T202021"
---
#+end_src

For Markdown with TOML, it looks like this (~denote-file-type~ has the
=markdown-toml= value):

#+begin_src md
+++
title      = "This is a sample note"
date       = 2022-06-10
tags       = ["denote", "testing"]
identifier = "20220610T201510"
+++
#+end_src

And for plain text, we have the following (~denote-file-type~ has the
=text= value):

#+begin_example
title:      This is a sample note
date:       2022-06-10
tags:       denote  testing
identifier: 20220610T202232
---------------------------
#+end_example

#+vindex: denote-front-matter-date-format
The format of the date in the front matter is controlled by the user
option ~denote-front-matter-date-format~:

- When the value is nil (the default), the date uses a plain
 =YEAR-MONTH-DAY= notation, like =2022-06-08= (the ISO 8601 standard).

- When the value is the =org-timestamp= symbol, the date is recorded as
  an inactive Org timestamp, such as =[2022-06-08 Wed 06:19]=.

- An arbitrary string value is interpreted as the argument for the
  function ~format-time-string~.  This gives the user maximum control
  over how time is represented in the front matter.

When ~denote-file-type~ specifies one of the Markdown flavors, we ignore
this user option in order to enforce the RFC3339 specification (Markdown
is typically employed in static site generators as source code for Web
pages).  However, when ~denote-front-matter-date-format~ has a string
value, this rule is suspended: we use whatever the user wants.

** Tweaking the front matter
:PROPERTIES:
:CUSTOM_ID: h:f69371d5-1843-493d-9ff5-c1ab3b43024e
:END:

What follows is for advanced users.  When in doubt, only configure
variables we describe as a "user option": they are declared in the
source code with the ~defcustom~ keyword.

Denote's code base is designed in a composable way, which lets the user
make precise interventions to affect the output of the relevant
commands.  One such case is to configure the front matter, such as by
changing the order the keys appear in, renaming them, or adding new
elements.

Some examples are in order, starting with the Org file type.  This is
what we have in =denote.el=:

#+begin_src emacs-lisp
(defvar denote-org-front-matter
  ":PROPERTIES:
:ID:          %4$s
:END:
#+title:      %s
#+date:       %s
#+filetags:   %s
\n"
  "Org front matter value for `format'.
The order of the arguments is TITLE, DATE, KEYWORDS, ID.  If you
are an avdanced user who wants to edit this variable to affect
how front matter is produced, consider using something like %2$s
to control where Nth argument is placed.")
#+end_src

Notice how we can pass a number to the =%s= specifier for the =:ID:=
property.  This is what allows us to change the placement of the
provided arguments.

The default Org mode front matter is formatted as:

#+begin_src org
:PROPERTIES:
:ID: 20220610T202537
:END:
,#+title:      This is a sample note
,#+date:       2022-06-10
,#+filetags:   denote  testing
#+end_src

If the user does not need =org-id= compatible ID property drawer, they
can do this instead:

#+begin_src emacs-lisp
(setq denote-org-front-matter
      "#+title:     %s
,#+date:       %s
,#+filetags:   %s
,#+identifier: %s
\n"
      "Org front matter value for `format'.
The order of the arguments is TITLE, DATE, KEYWORDS, ID.  If you
are an avdanced user who wants to edit this variable to affect
how front matter is produced, consider using something like %2$s
to control where Nth argument is placed.")
#+end_src

The output is now formatted thus:

#+begin_src org
,#+title:      This is a sample note
,#+date:       2022-06-10
,#+filetags:   denote  testing
,#+identifier: 20220610T202537
#+end_src

For another example, we will use the plain text variant, as it differs a
bit from the above.  By default it is formatted this way:

#+begin_example
title:      This is a sample note
date:       2022-06-10
tags:       denote  testing
identifier: 20220610T202232
---------------------------
#+end_example

The line with the hyphens is the product of the fifth format specifier,
as documented in ~denote-text-front-matter~.  Its value is stored in
~denote-text-front-matter-delimiter~.  Say we want to have a delimiter
both at the top and bottom:

#+begin_src emacs-lisp
(setq denote-text-front-matter
      "%5$s
title:      %1$s
date:       %2$s
tags:       %3$s
identifier: %4$s
%5$s\n\n")
#+end_src

Which gives us:

#+begin_example
---------------------------
title:      This is a sample note
date:       2022-06-11
tags:       denote  testing
identifier: 20220611T093252
---------------------------
#+end_example

Or we would rather use another character instead of hyphens, such as the
equals sign:

#+begin_src emacs-lisp
(setq denote-text-front-matter-delimiter (make-string 27 ?=))
#+end_src

Remember that this is for advanced users.  If you want to see changes
done on this front, you are welcome to share your thoughts and/or
participate in the development of Denote.

* Linking notes
:PROPERTIES:
:CUSTOM_ID: h:fc913d54-26c8-4c41-be86-999839e8ad31
:END:

#+findex: denote-link
The ~denote-link~ command inserts a link at point to an entry specified
at the minibuffer prompt.  Links are formatted depending on the file
type of current note.  In Org and plain text buffers, links are
formatted thus: =[[denote:IDENTIFIER][TITLE]]=.  While in Markdown they
are expressed as =[TITLE](denote:IDENTIFIER)=.

When ~denote-link~ is called with a prefix argument (=C-u= by default)
it formats links like =[[denote:IDENTIFIER]]=.  The user might prefer
its simplicity.

#+vindex: denote-link-use-org-id
When the user option ~denote-link-use-org-id~ is set to non-nil (default
is nil), inserted links in Org notes that target other Org notes will
use the standard =id:= type so the format is =[[id:IDENTIFIER][TITLE]]=
(the title is omitted is ~denote-link~ is called with a prefix argument,
as explained above).  When, however, an Org note links to a note in
another file, the link with use our own =denote:= type as there is no
standard for this case.

Inserted links are automatically buttonized and remain active for as
long as the buffer is available.  In Org this is handled automatically
as Denote either uses the standard =id:= link type or creates its own
custom hyperlink: the =denote:= type which works exactly like the
=file:=.  In Markdown and plain text, Denote handles the buttonization
of those links.

To buttonize links in existing files while visiting them, the user must
add this snippet to their setup:

#+findex: denote-link-buttonize-buffer
#+begin_src emacs-lisp
(add-hook 'find-file-hook #'denote-link-buttonize-buffer)
#+end_src

#+findex: denote-link-find-file
Denote has a major-mode-agnostic mechanism to collect all linked file
references in the current buffer and return them as an appropriately
formatted list.  This list can then be used in interactive commands.
The ~denote-link-find-file~ is such a command.  It uses minibuffer
completion to visit a file that is linked to from the current note.  The
candidates have the correct metadata, which is ideal for integration
with other standards-compliant tools ([[#h:8ed2bb6f-b5be-4711-82e9-8bee5bb06ece][Extending Denote]]).  For instance,
a package such as =marginalia= will display accurate annotations, while
the =embark= package will be able to work its magic such as in exporting
the list into a filtered Dired buffer (i.e. a familiar Dired listing
with only the files of the current minibuffer session).

#+findex: denote-link-backlinks
The command ~denote-link-backlinks~ produces a bespoke buffer which
displays the file name of all notes linking to the current one.  Each
file name appears on its own line and is buttonized so that it performs
the action of visiting the referenced file.  The backlinks' buffer looks
like this:

#+begin_example
Backlinks to "On being honest" (20220614T130812)
------------------------------------------------

20220614T145606--let-this-glance-become-a-stare__journal.txt
20220616T182958--not-feeling-butterflies-in-your-stomach__journal.txt
#+end_example

#+vindex: denote-link-fontify-backlinks
The backlinks' buffer is fontified by default, though the user has
access to the ~denote-link-fontify-backlinks~ option to disable this
effect by setting its value to nil.

#+vindex: denote-link-backlinks-display-buffer-action
The placement of the backlinks' buffer is subject to the user option
~denote-link-backlinks-display-buffer-action~.  Due to the nature of the
underlying ~display-buffer~ mechanism, this inevitably is an advanced
feature.  By default, the backlinks' buffer is displayed below the
current window.  The doc string of our user option includes a
configuration that places the buffer in a left side window instead.
Reproducing it here for your convenience:

#+begin_src emacs-lisp
(setq denote-link-backlinks-display-buffer-action
      '((display-buffer-reuse-window
         display-buffer-in-side-window)
        (side . left)
        (slot . 99)
        (window-width . 0.3)))
#+end_src

#+findex: denote-link-add-links
The command ~denote-link-add-links~ adds links at point matching a
regular expression or plain string.  The links are inserted as a
typographic list, such as:

#+begin_example
- link1
- link2
- link3
#+end_example

Each link is formatted according to the file type of the current note,
as explained further above about the ~denote-link~ command.  The current
note is excluded from the matching entries (adding a link to itself is
pointless).

When called with a prefix argument (=C-u=) ~denote-link-add-links~ will
format all links as =[[TYPE:IDENTIFIER]]=, hence a typographic list:

#+begin_example
- [[TYPE:IDENTIFIER-1]]
- [[TYPE:IDENTIFIER-2]]
- [[TYPE:IDENTIFIER-3]]
#+end_example

The =TYPE= is either =denote:= or =id:=, exactly as we explained above
for the ~denote-link~ command.

Same examples of a regular expression that can be used with this
command:

- =journal= match all files which include =journal= anywhere in their
  name.

- =_journal= match all files which include =journal= as a keyword.

- =^2022.*_journal= match all file names starting with =2022= and
  including the keyword =journal=.

- =\.txt= match all files including =.txt=.  In practical terms, this
  only applies to the file extension, as Denote automatically removes
  dots (and other characters) from the base file name.

If files are created with ~denote-sort-keywords~ as non-nil (the
default), then it is easy to write a regexp that includes multiple
keywords in alphabetic order:

- =_denote.*_package= match all files that include both the =denote= and
 =package= keywords, in this order.

- =\(.*denote.*package.*\)\|\(.*package.*denote.*\)= is the same as
  above, but out-of-order.

Remember that regexp constructs only need to be escaped once (like =\|=)
when done interactively but twice when called from Lisp.  What we show
above is for interactive usage.

#+findex: denote-link-insert-link
#+findex: denote-link-show-backlinks-buffer
#+findex: denote-link-insert-links-matching-regexp
For convenience, the ~denote-link~ command has an alias called
~denote-link-insert-link~.  The ~denote-link-backlinks~ can also be used
as ~denote-link-show-backlinks-buffer~.  While ~denote-link-add-links~
is aliased ~denote-link-insert-links-matching-regexp~.  The purpose of
these aliases is to offer alternative, more descriptive names of select
commands.

** Writing metanotes
:PROPERTIES:
:CUSTOM_ID: h:6060a7e6-f179-4d42-a9de-a9968aaebecc
:END:

A "metanote" is an entry that describes other entries who have something
in common.  Writing metanotes can be part of a workflow where the user
periodically reviews their work in search of patterns and deeper
insights.  For example, you might want to read your journal entries from
the past year to reflect on your experiences, evolution as a person, and
the like.

The command ~denote-link-add-links~, which we covered extensively in the
previous section, is suited for this task ([[#h:fc913d54-26c8-4c41-be86-999839e8ad31][Linking notes]]).  You will
create your metanote the way you use Denote ordinarily (metanotes may
have the =metanote= keyword), write an introduction or however you want
to go about it, invoke ~denote-link-add-links~ to cite the notes that
match the given regexp, and continue writing.

Metanotes can serve as entry points to groupings of individual notes.
They are not the same as a filtered list of files, i.e. what you would
do in Dired or the minibuffer where you narrow the list of notes to a
given query.  Metanotes contain the filtered list plus your thoughts
about it.  The act of purposefully grouping notes together and
contemplating on their shared patterns is what adds value.

Your future self will appreciate metanotes for the function they serve
in encapsulating knowledge, while current you will be equipped with the
knowledge derived from the deliberate self-reflection.

* Fontification in Dired
:PROPERTIES:
:CUSTOM_ID: h:337f9cf0-9f66-45af-b73f-f6370472fb51
:END:

#+findex: denote-dired-mode
One of the upsides of Denote's file-naming scheme is the predictable
pattern it establishes, which appears as a near-tabular presentation in
a listing of notes (i.e. in Dired).  The ~denote-dired-mode~ can help
enhance this impression, by fontifying the components of the file name
to make the date (identifier) and keywords stand out.

There are two ways to set the mode.  Either use it for all directories,
which probably is not needed:

#+begin_src emacs-lisp
(require 'denote-dired)
(add-hook 'dired-mode-hook #'denote-dired-mode)
#+end_src

#+vindex: denote-dired-directories
#+findex: denote-dired-mode-in-directories
Or configure the user option ~denote-dired-directories~ and then set up
the function ~denote-dired-mode-in-directories~:

#+begin_src emacs-lisp
(require 'denote-dired)

;; We use different ways to specify a path for demo purposes.
(setq denote-dired-directories
      (list denote-directory
            (thread-last denote-directory (expand-file-name "attachments"))
            (expand-file-name "~/Documents/vlog")))

(add-hook 'dired-mode-hook #'denote-dired-mode-in-directories)
#+end_src

The faces we define are:

#+vindex: denote-dired-field-date
#+vindex: denote-dired-field-delimiter
#+vindex: denote-dired-field-extension
#+vindex: denote-dired-field-keywords
#+vindex: denote-dired-field-time
#+vindex: denote-dired-field-title
+ ~denote-dired-field-date~
+ ~denote-dired-field-delimiter~
+ ~denote-dired-field-extension~
+ ~denote-dired-field-keywords~
+ ~denote-dired-field-time~
+ ~denote-dired-field-title~

For the time being, the =diredfl= package is not compatible with this
facility.

The ~denote-dired-mode~ does not only fontify note files that were
created by Denote: it covers every file name that follows our naming
conventions ([[#h:4e9c7512-84dc-4dfb-9fa9-e15d51178e5d][The file-naming scheme]]).  This is particularly useful for
scenaria where, say, one wants to organise their collection of PDFs and
multimedia in a systematic way (and, perhaps, use them as attachments
for the notes Denote produces).

* Minibuffer histories
:PROPERTIES:
:CUSTOM_ID: h:82dc1203-d689-44b2-9a6c-b37776209651
:END:

Denote has a dedicated minibuffer history for each one of its prompts.
This practically means that using =M-p= (~previous-history-element~) and
=M-n= (~next-history-element~) will only cycle through the relevant
record of inputs, such as your latest titles in the =TITLE= prompt, and
keywords in the =KEYWORDS= prompt.

The built-in =savehist= library saves minibuffer histories.  Sample
configuration:

#+begin_src emacs-lisp
(require 'savehist)
(setq savehist-file (locate-user-emacs-file "savehist"))
(setq history-length 10000)
(setq history-delete-duplicates t)
(setq savehist-save-minibuffer-history t)
(add-hook 'after-init-hook #'savehist-mode)
#+end_src

* Notes in multiple file types
:PROPERTIES:
:CUSTOM_ID: h:f34b172b-3440-446c-aec1-bf818d0aabfe
:END:

As noted before, Denote does not have a particular preference on the
workflow the user wishes to follow nor does it expect a specific file
type.  It is entirely possible to store notes in a variety of formats
across multiple directories and Denote will still be able to work with
them, provided they follow the file-naming scheme and have an identifier
in their front matter, where relevant.  Here we show how to create new
notes that take the example of the ~denote-type~ command and take it one
step further.

Suppose you want to use the ~denote~ command to store some notes in
Markdown, others in Org, and others still in plain text.  Maybe you also
want to place each of those in its own directory.  Using the
~denote-type~ command is not sufficient, as it only operates on the
value of the user option ~denote-directory~.  You need some small
wrapper functions.

For example:

+ =~/Documents/notes/= is your default and contains Org files.
+ =~/Documents/blog/= holds the files of your blog.
+ =~/Documents/random/= is where you scribble thoughts in plain text.

Why would you do that?  It does not matter.  This is for didactic
purposes.  All you need to do is write functions that ~let~ bind the
~denote-directory~ and to the desired value.

#+begin_src emacs-lisp
(defun my-denote-markdown-toml ()
  "Create Markdown+TOML note in ~/Documents/blog/."
  (interactive)
  (let ((denote-file-type 'markdown-toml)
        (denote-directory "~/Documents/blog/"))
    (call-interactively #'denote)))

(defun my-denote-plain-text ()
  "Create plain text note in ~/Documents/random/."
  (interactive)
  (let ((denote-file-type 'text)
        (denote-directory "~/Documents/random/"))
    (call-interactively #'denote)))
#+end_src

You do not need a third command for the Org files, as those would be the
default used by regular ~denote~.

Given Denote's composable code, you can tweak the output however you
like, including the contents of the file ([[#h:f69371d5-1843-493d-9ff5-c1ab3b43024e][Tweaking the front matter]]).

If you do place different types of notes in their own directories, you
must introduce directory-local variables to keep things working
seamlessly.  Otherwise you cannot create notes, retrieve backlinks, and
so on.  To that end, the ~denote-directory~ variable considers the
symbols =default-directory= or =local= as safe local variables.  Write a
=.dir-locals.el= file in each of your non-default notes directories with
the following contents (replacing =default-directory= with =local=, if
you prefer):

#+begin_src emacs-lisp
;;; Directory Local Variables
;;; For more information see (info "(emacs) Directory Variables")

((nil . ((denote-directory . default-directory))))
#+end_src

This will allow things to work smoothly (e.g. ~denote-infer-keywords~).

Your default ~denote-directory~ does not need this, as it already is the
normal target that Denote uses.

Want to automate aspects of note creation ([[#h:4a6d92dd-19eb-4fcc-a7b5-05ce04da3a92][Keep a journal or diary]])?
Have more ideas?  Something does not work quite right?  Areas you wish
were more abstract in the code?  Please participate in the development
process.

** Keep a journal or diary
:PROPERTIES:
:CUSTOM_ID: h:4a6d92dd-19eb-4fcc-a7b5-05ce04da3a92
:END:

While there are subtle technical differences between a journal and a
diary, we will consider those equivalent in the interest of brevity:
they both describe a personal space that holds a record of your thoughts
about your experiences and/or view of events in the world.

Suppose you are committed to writing an entry every day.  Unlike what we
demonstrated before, your writing will follow a regular naming pattern
([[#h:f34b172b-3440-446c-aec1-bf818d0aabfe][Notes in multiple file types]]).  You know that the title of the new note
must always look like =Tuesday 14 June 2022= and the keyword has to be
=journal= or =diary=.  As such, you want to automate the task instead of
being prompted each time, as is the norm with ~denote~ and the relevant
commands ([[#h:17896c8c-d97a-4faa-abf6-31df99746ca6][Points of entry]]).  This is easy to accomplish because ~denote~
can be called from Lisp and given the required arguments of =TITLE= and
=KEYWORDS= directly.  All you need is a simple wrapper function:

#+begin_src emacs-lisp
(defun my-denote-journal ()
  "Create an entry tagged 'journal' with the date as its title."
  (interactive)
  (denote
   (format-time-string "%A %e %B %Y") ; format like Tuesday 14 June 2022
   "journal")) ; multiple keywords are a list of strings: '("one" "two")
#+end_src

By invoking ~my-denote-journal~ you will go straight into the newly
created note and commit to your writing outright.

Of course, you can always set up the function so that it asks for a
=TITLE= but still automatically applies the =journal= tag:

#+begin_src emacs-lisp
(defun denote-journal-with-title ()
  "Create an entry tagged 'journal', while prompting for a title."
  (interactive)
  (denote
   (denote--title-prompt) ; ask for title, instead of using human-readable date
   "journal"))
#+end_src

Sometimes journaling is done with the intent to hone one's writing
skills.  Perhaps you are learning a new language or wish to communicate
your ideas with greater clarity and precision.  As with everything that
requires a degree of sophistication, you have to work for it---write,
write, write!

One way to test your progress is to set a timer.  It helps you gauge
your output and its quality.  To use a timer with Emacs, consider the
=tmr= package:

#+begin_src emacs-lisp
(defun my-denote-journal-with-tmr ()
  "Like `my-denote-journal', but also set a 10-minute timer.
The `tmr' command is part of the `tmr' package."
  (interactive)
  (denote
   (format-time-string "%A %e %B %Y")
   "journal")
  (tmr 10 "Practice writing in my journal")) ; set 10 minute timer with a description
#+end_src

Once the timer elapses, stop writing and review your performance.
Practice makes perfect!

[ As Denote matures, we may add hooks to control what happens before or
  after the creation of a new note.  We shall also document more
  examples of tasks that can be accomplished with this package. ]

Sources for =tmr=:

+ Package name (GNU ELPA): =tmr=
+ Official manual: <https://protesilaos.com/emacs/tmr>
+ Change log: <https://protesilaos.com/emacs/denote-changelog>
+ Git repo on SourceHut: <https://git.sr.ht/~protesilaos/tmr>
  - Mirrors:
    + GitHub: <https://github.com/protesilaos/tmr>
    + GitLab: <https://gitlab.com/protesilaos/tmr>
+ Mailing list: <https://lists.sr.ht/~protesilaos/tmr>

Recall what we discussed elsewhere in the manual about changing the file
type and target directory ([[#h:f34b172b-3440-446c-aec1-bf818d0aabfe][Notes in multiple file types]]).  You basically
~let~ bind the relevant variables.  Such bindings are specific to the
function: they do not affect anything outside of it, so you can keep the
defaults for your regular notes and use something different for your
journaling.  For example, the following snippet is like the previous
sample of writing a journal entry and setting a timer, but it also uses
a plain text file type and adds the new note to the
=~/Documents/journal/= directory:

#+begin_src emacs-lisp
(defun my-denote-journal-with-tmr-and-custom-type-and-dir ()
  "Like `my-denote-journal-with-tmr' with custom type and directory."
  (interactive)
  (let ((denote-file-type 'text) ; it supports other file types as well: read its doc string
        (denote-directory "~/Documents/journal/"))
    (denote
     (format-time-string "%A %e %B %Y")
     "journal")
    (tmr 10 "Practice writing in my journal")))
#+end_src

Finally, we can incorporate the idea of the ~denote-date~ command into
our journaling workflow.  Unlike regular ~denote~, this command has a
slightly different structure.  Below are variants of the aforementioned
ideas.  If you pick more than one, just give them a unique name (the
text right after ~defun~):

#+begin_src emacs-lisp
(defun my-denote-journal-with-date (date title)
  "Ask for DATE and TITLE to write a journal entry.

Read the doc string of `denote-date' on what a valid DATE is."
  (interactive
   (list
    (denote--date-prompt)
    (denote--title-prompt)))
  (when-let ((d (denote--valid-date date))
             (id (format-time-string denote--id-format d))
             ((denote--barf-duplicate-id id)))
    (denote--prepare-note title "journal" nil d id)))

(defun my-denote-journal-with-date (date)
  "Ask for DATE to write a journal entry.

Read the doc string of `denote-date' on what a valid DATE input is.

The title of the note is something like Tuesday 17 June 2020,
though you can modify the `format-time-string' specifiers as
described in its doc string."
  (interactive (list (denote--date-prompt)))
  (when-let ((d (denote--valid-date date))
             (id (format-time-string denote--id-format d))
             ((denote--barf-duplicate-id id)))
    (denote--prepare-note
     (format-time-string "%A %e %B %Y" d)
     "journal" nil d id)))

(defun my-denote-journal-with-date (date)
  "Ask for DATE to write a journal entry.

Journal entries are stored in ~/Documents/journal/ and use plain
text for their `denote-file-type'.

Read the doc string of `denote-date' on what a valid DATE input is.

The title of the note is something like Tuesday 17 June 2020,
though you can modify the `format-time-string' specifiers as
described in its doc string."
  (interactive (list (denote--date-prompt)))
  (when-let ((d (denote--valid-date date))
             (id (format-time-string denote--id-format d))
             ((denote--barf-duplicate-id id))
             (denote-file-type 'text) ; it supports other file types as well: read its doc string
             (denote-directory "~/Documents/journal/"))
    (denote--prepare-note
     (format-time-string "%A %e %B %Y" d)
     "journal" nil d id)))

(defun my-denote-journal-with-date (date)
  "Ask for DATE to write a journal entry and start a 10-minute tmr.

Journal entries are stored in ~/Documents/journal/ and use plain
text for their `denote-file-type'.  The `tmr' command comes from
the package of the same name (same dev as Denote's).

Read the doc string of `denote-date' on what a valid DATE input is.

The title of the note is something like Tuesday 17 June 2020,
though you can modify the `format-time-string' specifiers as
described in its doc string."
  (interactive (list (denote--date-prompt)))
  (when-let ((d (denote--valid-date date))
             (id (format-time-string denote--id-format d))
             ((denote--barf-duplicate-id id))
             (denote-file-type 'text) ; it supports other file types as well: read its doc string
             (denote-directory "~/Documents/journal/"))
    (denote--prepare-note
     (format-time-string "%A %e %B %Y" d)
     "journal" nil d id)
    (tmr 10 "Practice writing in my journal")))
#+end_src

* Extending Denote
:PROPERTIES:
:CUSTOM_ID: h:8ed2bb6f-b5be-4711-82e9-8bee5bb06ece
:END:

Denote is a tool with a narrow scope: create notes and link between
them, based on the aforementioned file-naming scheme.  For other common
operations the user is advised to rely on standard Emacs facilities or
specialised third-party packages.  This section covers the details.

** Narrow the list of files in Dired
:PROPERTIES:
:CUSTOM_ID: h:ea173a01-69ef-4574-89a7-6e60ede02f13
:END:

Emacs' standard file manager (or directory editor) can read a regular
expression to mark the matching files.  This is the command
~dired-mark-files-regexp~, which is bound to =% m= by default.  For
example, =% m _denote= will match all files that have the =denote=
keyword ([[#h:1a953736-86c2-420b-b566-fb22c97df197][Features of the file-naming scheme for searching or filtering]]).

Once the files are matched, the user has to options: (i) narrow the list
to the matching items or (ii) exclude the matching items from the list.

For the former, we want to toggle the marks by typing =t= (calls the
command ~dired-toggle-marks~ by default) and then hit the letter =k=
(for ~dired-do-kill-lines~).  The remaining files are those that match
the regexp that was provided earlier.

For the latter approach of filtering out the matching items, simply
involves the use of the =k= command (~dired-do-kill-lines~) to omit the
marked files from the list.

These sequences can be combined to incrementally narrow the list.  Note
that ~dired-do-kill-lines~ does not delete files: it simply hides them
from the current view.

Revert to the original listing with =g= (~revert-buffer~).

For a convenient wrapper, consider this example:

#+begin_src emacs-lisp
(defvar prot-dired--limit-hist '()
  "Minibuffer history for `prot-dired-limit-regexp'.")

;;;###autoload
(defun prot-dired-limit-regexp (regexp omit)
  "Limit Dired to keep files matching REGEXP.

With optional OMIT argument as a prefix (\\[universal-argument]),
exclude files matching REGEXP.

Restore the buffer with \\<dired-mode-map>`\\[revert-buffer]'."
  (interactive
   (list
    (read-regexp
     (concat "Files "
             (when current-prefix-arg
               (propertize "NOT " 'face 'warning))
             "matching PATTERN: ")
     nil 'prot-dired--limit-hist)
    current-prefix-arg))
  (dired-mark-files-regexp regexp)
  (unless omit (dired-toggle-marks))
  (dired-do-kill-lines))
#+end_src

** Use Embark to collect minibuffer candidates
:PROPERTIES:
:CUSTOM_ID: h:edf9b651-86eb-4d5f-bade-3c9e270082f0
:END:

=embark= is a remarkable package that lets you perform relevant,
context-dependent actions using a prefix key (simplifying in the
interest of brevity).

For our purposes, Embark can be used to produce a Dired listing directly
from the minibuffer.  Suppose the current note has links to three other
notes.  You might use the ~denote-link-find-file~ command to pick one
via the minibuffer.  But why not turn those three links into their own
Dired listing?  While in the minibuffer, invoke ~embark-act~ which you
may have already bound to =C-.= and then follow it up with =E= (for the
~embark-export~ command).

This pattern can be repeated with any list of candidates, meaning that
you can narrow the list by providing some input before eventually
exporting the results with Embark.

Overall, this is very powerful and you might prefer it over doing the
same thing directly in Dired, since you also benefit from all the power
of the minibuffer ([[#h:ea173a01-69ef-4574-89a7-6e60ede02f13][Narrow the list of files in Dired]]).

** Search file contents
:PROPERTIES:
:CUSTOM_ID: h:76198fab-d6d2-4c67-9ccb-7a08cc883952
:END:

Emacs provides built-in commands which are wrappers of standard Unix
tools: =M-x grep= lets the user input the flags of a ~grep~ call and
pass a regular expression to the =-e= flag.

The author of Denote uses this thin wrapper instead:

#+begin_src emacs-lisp
(defvar prot-search--grep-hist '()
  "Input history of grep searches.")

;;;###autoload
(defun prot-search-grep (regexp &optional recursive)
  "Run grep for REGEXP.

Search in the current directory using `lgrep'.  With optional
prefix argument (\\[universal-argument]) for RECURSIVE, run a
search starting from the current directory with `rgrep'."
  (interactive
   (list
    (read-from-minibuffer (concat (if current-prefix-arg
                                      (propertize "Recursive" 'face 'warning)
                                    "Local")
                                  " grep for PATTERN: ")
                          nil nil nil 'prot-search--grep-hist)
    current-prefix-arg))
  (unless grep-command
    (grep-compute-defaults))
  (if recursive
      (rgrep regexp "*" default-directory)
    (lgrep regexp "*" default-directory)))
#+end_src

Rather than maintain custom code, consider using the excellent =consult=
package: it provides commands such as ~consult-grep~ and ~consult-find~
which provide live results and are generally easier to use than the
built-in commands.

** Bookmark the directory with the notes
:PROPERTIES:
:CUSTOM_ID: h:1bba4c1e-6812-4749-948f-57df4fd49b36
:END:

Part of the reason Denote does not reinvent existing functionality is to
encourage you to learn more about Emacs.  You do not need a bespoke
"jump to my notes" directory because such commands do not scale well.
Will you have a "jump to my downloads" then another for multimedia and
so on?  No.

Emacs has a built-in framework for recording persistent markers to
locations.  Visit the ~denote-directory~ (or any dir/file for that
matter) and invoke the ~bookmark-set~ command (bound to =C-x r m= by
default).  It lets you create a bookmark.

The list of bookmarks can be reviewed with the ~bookmark-bmenu-list~
command (bound to =C-x r l= by default).  A minibuffer interface is
available with ~bookmark-jump~ (=C-x r b=).

If you use the =consult= package, its default ~consult-buffer~ command
has the means to group together buffers, recent files, and bookmarks.
Each of those types can be narrowed to with a prefix key.  The package
=consult-dir= is an extension to =consult= which provides useful extras
for working with directories, including bookmarks.

** Use the consult-notes package
:PROPERTIES:
:CUSTOM_ID: h:8907f4bc-992a-45bc-a60e-267ed1ce9c2d
:END:

If you are already using =consult= (which is a brilliant package), you
will probably like its =consult-notes= extension.  It uses the familiar
mechanisms of Consult to filter searches via a prefix key.  For example:

#+begin_src emacs-lisp
(setq consult-notes-data-dirs
      `(("Notes"  ?n ,denote-directory)
        ("Books"  ?b "~/Documents/books")))
#+end_src

With the above, =M-x consult-notes= will list the files in those two
directories.  If you type =n= and space, it narrows the list to just the
notes, while =b= does the same for books.

Note that =consult-notes= is in its early stages of development.  Expect
improvements in the near future (written on 2022-06-22 16:48 +0300).

** Treat your notes as a project
:PROPERTIES:
:CUSTOM_ID: h:fad3eb08-ddc7-43e4-ba28-210d89668037
:END:

Emacs a built-in library for treating a directory tree as a "project".
This means that the contents of this tree are seen as part of the same
set, so commands like ~project-switch-to-buffer~ (=C-x p b= by default)
will only consider buffers in the current project (e.g. three notes that
are currently being visited).

Normally, a "project" is a directory tree whose root is under version
control.  For our purposes, all you need is to navigate to the
~denote-directory~ (for the shell or via Dired) and use the command-line
to run this (requires the =git= executable):

: git init

From Dired, you can type =M-!= which invokes ~dired-smart-shell-command~
and then run the git call there.

The project can then be registered by invoking any project-related
command inside of it, such as ~project-find-file~ (=C-x p f=).

It is a good idea to keep your notes under version control, as that
gives you a history of changes for each file.  We shall not delve into
the technicalities here, though suffice to note that Emacs' built-in
version control framework or the exceptionally well-crafted =magit=
package will get the job done (VC can work with other backends besides
Git).

* Installation
:PROPERTIES:
:CUSTOM_ID: h:f3bdac2c-4704-4a51-948c-a789a2589790
:END:
#+cindex: Installation instructions

** GNU ELPA package
:PROPERTIES:
:CUSTOM_ID: h:42953f87-82bd-43ec-ab99-22b1e22955e7
:END:

The package is available as =denote=.  Simply do:

: M-x package-refresh-contents
: M-x package-install

And search for it.

GNU ELPA provides the latest stable release.  Those who prefer to follow
the development process in order to report bugs or suggest changes, can
use the version of the package from the GNU-devel ELPA archive.  Read:
https://protesilaos.com/codelog/2022-05-13-emacs-elpa-devel/.

** Manual installation
:PROPERTIES:
:CUSTOM_ID: h:d397712c-c8c0-4cfa-ad1a-ef28cf78d1f0
:END:

Assuming your Emacs files are found in =~/.emacs.d/=, execute the
following commands in a shell prompt:

#+begin_src sh
cd ~/.emacs.d

# Create a directory for manually-installed packages
mkdir manual-packages

# Go to the new directory
cd manual-packages

# Clone this repo, naming it "denote"
git clone https://git.sr.ht/~protesilaos/denote denote
#+end_src

Finally, in your =init.el= (or equivalent) evaluate this:

#+begin_src emacs-lisp
;; Make Elisp files in that directory available to the user.
(add-to-list 'load-path "~/.emacs.d/manual-packages/denote")
#+end_src

Everything is in place to set up the package.

* Sample configuration
:PROPERTIES:
:CUSTOM_ID: h:5d16932d-4f7b-493d-8e6a-e5c396b15fd6
:END:
#+cindex: Package configuration

#+begin_src emacs-lisp
(require 'denote)

;; Remember to check the doc strings of those variables.
(setq denote-directory (expand-file-name "~/Documents/notes/"))
(setq denote-known-keywords
      '("emacs" "philosophy" "politics" "economics"))
(setq denote-infer-keywords t)
(setq denote-sort-keywords t)
(setq denote-file-type nil) ; Org is the default, set others here

;; We allow multi-word keywords by default.  The author's personal
;; preference is for single-word keywords for a more rigid workflow.
(setq denote-allow-multi-word-keywords t)

(setq denote-front-matter-date-format nil) ; change this to `org-timestamp' or custom string

;; You will not need to `require' all those individually once the
;; package is available.
(require 'denote-retrieve)
(require 'denote-link)

;; If you want links to and from Org notes to use the standard 'id:'
;; link type instead of 'denote:'.
(setq denote-link-use-org-id t)

;; By default, we fontify backlinks in their bespoke buffer.
(setq denote-link-fontify-backlinks t)

;; Also see `denote-link-backlinks-display-buffer-action' which is a bit
;; advanced.

;; If you use Markdown or plain text files (Org renders links as buttons
;; right away)
(add-hook 'find-file-hook #'denote-link-buttonize-buffer)

(require 'denote-dired)
(setq denote-dired-rename-expert nil)

;; We use different ways to specify a path for demo purposes.
(setq denote-dired-directories
      (list denote-directory
            (thread-last denote-directory (expand-file-name "attachments"))
            (expand-file-name "~/Documents/books")))

;; Generic (great if you rename files Denote-style in lots of places):
;; (add-hook 'dired-mode-hook #'denote-dired-mode)
;;
;; OR if only want it in `denote-dired-directories':
(add-hook 'dired-mode-hook #'denote-dired-mode-in-directories)

;; Here is a custom, user-level command from one of the examples we
;; showed in this manual.  We define it here and add it to a key binding
;; below.
(defun my-denote-journal ()
  "Create an entry tagged 'journal', while prompting for a title."
  (interactive)
  (denote
   (denote--title-prompt)
   "journal"))

;; Denote does not define any key bindings.  This is for the user to
;; decide.  For example:
(let ((map global-map))
  (define-key map (kbd "C-c n j") #'my-denote-journal) ; our custom command
  (define-key map (kbd "C-c n n") #'denote)
  (define-key map (kbd "C-c n N") #'denote-type)
  (define-key map (kbd "C-c n d") #'denote-date)
  ;; If you intend to use Denote with a variety of file types, it is
  ;; easier to bind the link-related commands to the `global-map', as
  ;; shown here.  Otherwise follow the same pattern for `org-mode-map',
  ;; `markdown-mode-map', and/or `text-mode-map'.
  (define-key map (kbd "C-c n i") #'denote-link) ; "insert" mnemonic
  (define-key map (kbd "C-c n I") #'denote-link-add-links)
  (define-key map (kbd "C-c n l") #'denote-link-find-file) ; "list" links
  (define-key map (kbd "C-c n b") #'denote-link-backlinks)
  ;; Note that `denote-dired-rename-file' can work from any context, not
  ;; just Dired bufffers.  That is why we bind it here to the
  ;; `global-map'.
  (define-key map (kbd "C-c n r") #'denote-dired-rename-file))

(with-eval-after-load 'org-capture
  (require 'denote-org-capture)
  (setq denote-org-capture-specifiers "%l\n%i\n%?")
  (add-to-list 'org-capture-templates
               '("n" "New note (with denote.el)" plain
                 (file denote-last-path)
                 #'denote-org-capture
                 :no-save t
                 :immediate-finish nil
                 :kill-buffer t
                 :jump-to-captured t)))
#+end_src

* Contributing
:PROPERTIES:
:CUSTOM_ID: h:1ebe4865-c001-4747-a6f2-0fe45aad71cd
:END:

Denote is a GNU ELPA package.  As such, any significant change to the
code requires copyright assignment to the Free Software Foundation (more
below).

You do not need to be a programmer to contribute to this package.
Sharing an idea or describing a workflow is equally helpful, as it
teaches us something we may not know and might be able to cover either
by extending Denote or expanding this manual ([[#h:044a6a0f-e382-4013-8279-8bf4e64e73c0][Things to do]]).  If you
prefer to write a blog post, make sure you share it with us: we can add
a section herein referencing all such articles.  Everyone gets
acknowledged ([[#h:f8126820-3b59-49fa-bcc2-73bd60132bb9][Acknowledgements]]).  There is no such thing as an
"insignificant contribution"---they all matter.

+ Package name (GNU ELPA): =denote=
+ Official manual: <https://protesilaos.com/emacs/denote>
+ Change log: <https://protesilaos.com/emacs/denote-changelog>
+ Git repo on SourceHut: <https://git.sr.ht/~protesilaos/denote>
  - Mirrors:
    + GitHub: <https://github.com/protesilaos/denote>
    + GitLab: <https://gitlab.com/protesilaos/denote>
+ Mailing list: <https://lists.sr.ht/~protesilaos/denote>

If our public media are not suitable, you are welcome to contact me
(Protesilaos) in private: <https://protesilaos.com/contact>.

Copyright assignment is a prerequisite to sharing code.  It is a simple
process.  Check the request form below (please adapt it accordingly).
You must write an email to the address mentioned in the form and then
wait for the FSF to send you a legal agreement.  Sign the document and
file it back to them.  This could all happen via email and take about a
week.  You are encouraged to go through this process.  You only need to
do it once.  It will allow you to make contributions to Emacs in
general.

#+begin_example text
Please email the following information to assign@gnu.org, and we
will send you the assignment form for your past and future changes.

Please use your full legal name (in ASCII characters) as the subject
line of the message.

REQUEST: SEND FORM FOR PAST AND FUTURE CHANGES

[What is the name of the program or package you're contributing to?]

GNU Emacs

[Did you copy any files or text written by someone else in these changes?
Even if that material is free software, we need to know about it.]

Copied a few snippets from the same files I edited.  Their author,
Protesilaos Stavrou, has already assigned copyright to the Free Software
Foundation.

[Do you have an employer who might have a basis to claim to own
your changes?  Do you attend a school which might make such a claim?]


[For the copyright registration, what country are you a citizen of?]


[What year were you born?]


[Please write your email address here.]


[Please write your postal address here.]





[Which files have you changed so far, and which new files have you written
so far?]

#+end_example

* Things to do
:PROPERTIES:
:CUSTOM_ID: h:044a6a0f-e382-4013-8279-8bf4e64e73c0
:END:

Denote should work well for what is described in this manual.  Though we
can always do better.  These are some of the tasks that are planned for
the future and which you might want to help with ([[#h:1ebe4865-c001-4747-a6f2-0fe45aad71cd][Contributing]]).

This is a non-exhaustive list and you are always welcome to either
report or work on something else.

- [X] Buttonize =denote:= links in Markdown and plain text, but not Org.
- [X] Experiment with switch to =id:= link type instead of =denote:=.
- [ ] Ensure integration between =denote:= links and Embark.
- [ ] Add command that expands the identifier in links to a full name.
- [ ] Add command that rewrites full names in links, if they are invalid.
- [ ] Consider completion-at-point after =denote:= links.
- [ ] Support mutually-exclusive sets of tags.

These are just ideas.  We need to consider the pros and cons in each
case and act accordingly.

* Alternatives to Denote
:PROPERTIES:
:CUSTOM_ID: h:dbb51a1b-90b8-48e8-953c-e2fb3e36981e
:END:

What follows is a list of Emacs packages for note-taking.  I
(Protesilaos) have not used any of them, as I was manually applying my
file-naming scheme beforehand and by the time those packages were
available I was already hacking on the predecessor of Denote as a means
of learning Emacs Lisp (a package which I called "Unassuming Sidenotes
of Little Significance", aka "USLS" which is pronounced as "U-S-L-S" or
"useless").  As such, I cannot comment at length on the differences
between Denote and each of those packages, beside what I gather from
their documentation.

+ [[https://github.com/org-roam/org-roam][org-roam]] :: The de facto standard in the Emacs milieu---and rightly
  so!  It has a massive community, is featureful, and should be an
  excellent companion to anyone who is invested in the Org ecosystem
  and/or knows what "Roam" is (I don't).  It has been explained to me
  that Org Roam uses a database to store a cache about your notes.  It
  otherwise uses standard Org files.  The cache helps refer to the same
  node through aliases which can provide lots of options.  Personally, I
  follow a single-topic-per-note approach, so anything beyond that is
  overkill.  If the database is only for a cache, then maybe that has no
  downside, though I am careful with any kind of specialised program as
  it creates a dependency.  If you ask me about database software in
  particular, I have no idea how to use one, let alone debug it or
  retrieve data from it if something goes awry (I could learn, but that
  is beside the point).

+ [[https://github.com/localauthor/zk][zk (or zk.el)]] :: Reading its documentation makes me think that this is
  Denote's sibling---the two projects have a lot of things in common,
  including the preference to rely on plain files and standard tools.
  The core difference is that Denote has a strict file-naming scheme.
  Other differences in available features are, in principle, matters of
  style or circumstance: both packages can have them.  As its initials
  imply, ZK enables a zettelkasten-like workflow.  It does not enforce
  it though, letting the user adapt the method to their needs and
  requirements.

+ [[https://github.com/ymherklotz/emacs-zettelkasten][zettelkasten]] :: This is another one of Denote's relatives, at least
  insofar as the goal of simplicity is concerned.  The major difference
  is that according to its documentation "the name of the file that is
  created is just a unique ID".  This is not consistent with our
  file-naming scheme which is all about making sense of your files by
  their name alone and being able to visually parse a listing of them
  without any kind of specialised tool (e.g. =ls -l= or =ls -C= on the
  command-line from inside the ~denote-directory~ give you a
  human-readable set of files names, while =find * -maxdepth 0 -type f=
  is another approach).

+ [[https://github.com/EFLS/zetteldeft][zetteldeft]] :: This is a zettelkasten note-taking system built on top
  of the =deft= package.  Deft provides a search interface to a
  directory, in this case the one holding the user's =zetteldeft= notes.
  Denote has no such dependency and is not opinionated about how the
  user prefers to search/access their notes: use Dired, Grep, the
 =consult= package, or whatever else you already have set up for all
  things Emacs, not just your notes.

Searching through =M-x list-packages= for "zettel" brings up more
matches. =zetteldesk= is an extension to Org Roam and, as such, I
cannot possibly know what Org Roam truly misses and what the added-value
of this package is. =neuron-mode= builds on top of an external program
called =neuron=, which I have never used.

Searching for "note" gives us a few more results. =notes-mode= has
precious little documentation and I cannot tell what it actually does
(as I said in my presentation for LibrePlanet 2022, inadequate docs are
a bug). =side-notes= differs from what we try to do with Denote, as it
basically gives you the means to record your thoughts about some other
project you are working on and keep them on the side: so it and Denote
should not be mutually exclusive.

If I missed something, please let me know.

** Alternative ideas wih Emacs and further reading
:PROPERTIES:
:CUSTOM_ID: h:188c0986-f2fa-444f-b493-5429356e75cf
:END:

This section covers blog posts from the Emacs community on the matter of
note-taking.  They may reference some of the packages covered in the
previous section or provide their custom code ([[#h:dbb51a1b-90b8-48e8-953c-e2fb3e36981e][Alternatives to Denote]]).
The list is unsorted.

+ José Antonio Ortega Ruiz (aka "jao") explains a note-taking method
  that is simple like Denote but differs in other ways.  An interesting
  approach overall: https://jao.io/blog/2022-06-19-simple-note-taking.html.

+ Jethro Kuan (the main =org-roam= developer) explains their note-taking
  techniques: https://jethrokuan.github.io/org-roam-guide/.  Good ideas
  all round, regardless of the package/code you choose to use.

[ Development note: help expand this list. ]

* Frequently Asked Questions
:PROPERTIES:
:CUSTOM_ID: h:da2944c6-cde6-4c65-8f2d-579305a159bb
:END:

I (Protesilaos) answer some questions I have received or might get.  It
is assumed that you have read the rest of this manual: I will not go
into the specifics of how Denote works.

** Why develop Denote when PACKAGE already exists?
:PROPERTIES:
:CUSTOM_ID: h:b875450a-ae22-4899-ac23-c10fa9c279bb
:END:

I wrote Denote because I was using a variant of Denote's file-naming
scheme before I was even an Emacs user (I switched to Emacs from
Tmux+Vim+CLI in the summer of 2019).  I was originally inspired by
Jekyll, the static site generator, which I started using for my website
in 2016 (was on WordPress before).  Jekyll's files follow the
=YYYY-MM-DD-TITLE.md= pattern.  I liked its efficiency relative to the
unstructured mess I had before.  Eventually, I started using that scheme
outside the confines of my website's source code.  Over time I refined
it and here we are.

Note-taking is something I take very seriously, as I am a prolific
writer (just check my website, which only reveals the tip of the
iceberg).  As such, I need a program that does exactly what I want and
which I know how to extend.  I originally tried to use Org capture
templates to create new files with a Denote-style file-naming scheme but
never managed to achieve it.  Maybe because ~org-capture~ has some
hard-coded assumptions or I simply am not competent enough to hack on
core Org facilities.  Whatever the case, an alternative was in order.

The existence of PACKAGE is never a good reason for me not to conduct my
own experiments for recreational, educational, or practical purposes.
When the question arises of "why not contribute to PACKAGE instead?" the
answer is that without me experimenting in the first place, I would lack
the skills for such a task.  Furthermore, contributing to another
package does not guarantee I get what I want in terms of workflow.

Whether you should use Denote or not is another matter altogether:
choose whatever you want.

** Why not rely exclusively on Org?
:PROPERTIES:
:CUSTOM_ID: h:b9831849-5c71-484e-b444-bac19cc13151
:END:

I think Org is one of Emacs' killer apps.  I also believe it is not the
right tool for every job.  When I write notes, I want to focus on
writing.  Nothing more.  I thus have no need for stuff like org-babel,
scheduling to-do items, clocking time, and so on.  The more "mental
dependencies" you add to your workflow, the heavier the burden you carry
and the less focused you are on the task at hand: there is always that
temptation to tweak the markup, tinker with some syntactic construct,
obsess about what ought to be irrelevant to writing as such.

In technical terms, I also am not fond of Org's code base (I understand
why it is the way it is---just commenting on the fact).  Ever tried to
read it?  You will routinely find functions that are tens-to-hundreds of
lines long and have all sorts of special casing.  As I am not a
programmer and only learnt to write Elisp through trial and error, I
have no confidence in my ability to make Org do what I want at that
level, hence =denote= instead of =org-denote= or something.

Perhaps the master programmer is one who can deal with complexity and
keep adding to it.  I am of the opposite view, as language---code
included---is at its communicative best when it is clear and accessible.

Make no mistake: I use Org for the agenda and also to write technical
documentation that needs to be exported to various formats, including
this very manual.

** Why care about Unix tools when you use Emacs?
:PROPERTIES:
:CUSTOM_ID: h:da1e2469-8f04-450b-a379-a854efa80a36
:END:

My notes form part of my longer-term storage.  I do not want to have to
rely on a special program to be able to read them or filter them.  Unix
is universal, at least as far as I am concerned.

Denote streamlines some tasks and makes things easier in general, which
is consistent with how Emacs provides a layer of interactivity on top of
Unix.  Still, Denote's utilities can, in principle, be implemented as
POSIX shell scripts (minus the Emacs-specific parts like fontification
in Dired or the buttonization of links).

Portability matters.  For example, in the future I might own a
smartphone, so I prefer not to require Emacs, Org, or some other
executable to access my files on the go.

Furthermore, I might want to share those files with someone.  If I make
Emacs a requirement, I am limiting my circle to a handful of relatively
advanced users.

Please don't misinterpret this: I am using Emacs full-time for my
computing and maintain a growing list of packages for it.  This is just
me thinking long-term.

** Why many small files instead of few large ones?
:PROPERTIES:
:CUSTOM_ID: h:7d2e7b8a-d484-4c1d-8688-17f70f242ad7
:END:

I have read that Org favours the latter method.  If true, I strongly
disagree with it because of the implicit dependency it introduces and
the way it favours machine-friendliness over human-readability in terms
of accessing information.  Notes are long-term storage.  I might want to
access them on (i) some device with limited features, (ii) print on
paper, (iii) share with another person who is not a tech wizard.

There are good arguments for few large files, but all either prioritize
machine-friendliness or presuppose the use of sophisticated tools like
Emacs+Org.

Good luck using =less= on a generic TTY to read a file with a zillion
words, headings, sub-headings, sub-sub-headings, property drawers, and
other constructs!  You will not get the otherwise wonderful folding of
headings the way you do in Emacs---do not take such features for
granted.

My point is that notes should be atomic to help the user---and
potentially the user's family, friends, acquaintances---make sense of
them in a wide range of scenaria.  The more program-agnostic your file
is, the better for you and/or everyone else you might share your
writings with.

Human-readability means that we optimize for what matters to us.  If (a)
you are the only one who will ever read your notes, (b) always have
access to good software like Emacs+Org, (c) do not care about printing
on paper, then Denote's model is not for you.  Maybe you need to tweak
some ~org-capture~ template to append a new entry to one mega file (I do
that for my Org agenda, by the way, as I explained before about using
the right tool for the job).

** I add TODOs to my files; will the many files slow down the Org agenda?
:PROPERTIES:
:CUSTOM_ID: h:63c2f8d4-79ed-4c55-b3ef-e048a05802c0
:END:

I have not tested it, but assume that yes, many files will slow down the
agenda.  Consider looking into one of Denote's alternatives, with
=org-roam= being the obvious choice ([[#h:dbb51a1b-90b8-48e8-953c-e2fb3e36981e][Alternatives to Denote]]).

Or, if you want my opinion, decouple your longer-term storage from your
ephemeral to-do list: Denote (and others) can be used for the former,
while you let standard Org work splendidly for the latter---that is what
I do, anyway.

** I want to sort by last modified, why won't Denote let me?
:PROPERTIES:
:CUSTOM_ID: h:a7fd5e0a-78f7-434e-aa2e-e150479c16e2
:END:

Denote does not sort files and will not reinvent tools that handle such
functionality.  This is the job of the file manager or command-line
executable that lists files.

I encourage you to read the manpage of the =ls= executable.  It will
help you in general, while it applies to Emacs as well via Dired.  The
gist is that you can update the =ls= flags that Dired uses on-the-fly:
type =C-u M-x dired-sort-toggle-or-edit= (=C-u s= by default) and append
=--sort=time= at the prompt.  To reverse the order, add the =-r= flag.
The user option ~dired-listing-switches~ sets your default preference.

** How do you handle the last modified case?
:PROPERTIES:
:CUSTOM_ID: h:764b5e87-cd22-4937-b5fc-af3892d6b3d8
:END:

Denote does not insert any meta data or heading pertaining to edits in
the file.  I am of the view that these either do not scale well or are
not descriptive enough.  Suppose you use a "lastmod" heading with a
timestamp: which lines where edited and what did the change amount to?

This is where an external program can be helpful.  Use a Version Control
System, such as Git, to keep track of all your notes.  Every time you
add a new file, record the addition.  Same for post-creation edits.
Your VCS will let you review the history of those changes.  For
instance, Emacs' built-in version control framework has a command that
produces a log of changes for the current file: =M-x vc-print-log=,
bound to =C-x v l= by default.  From there one can access the
corresponding diff output (use =M-x describe-mode= (=C-h m=) in an
unfamiliar buffer to learn more about it).  With Git in particular,
Emacs users have the option of the all-round excellent =magit= package.

In short: let Denote (or equivalent) create notes and link between them,
the file manager organise and provide access to files, search programs
deal with searching and narrowing, and version control software handle
the tracking of changes.

* Acknowledgements
:PROPERTIES:
:CUSTOM_ID: h:f8126820-3b59-49fa-bcc2-73bd60132bb9
:END:
#+cindex: Contributors

Denote is meant to be a collective effort.  Every bit of help matters.

+ Author/maintainer :: Protesilaos Stavrou.

+ Contributions to code or the manual :: Damien Cassou, Jack Baty,
  Kaushal Modi.

+ Ideas and/or user feedback :: Colin McLear, Damien Cassou, Frank
  Ehmsen, Jack Baty, Kaushal Modi, Sven Seebeck, Ypot.

Special thanks to Peter Povinec who helped refine the file-naming
scheme, which is the cornerstone of this project.

* GNU Free Documentation License
:PROPERTIES:
:APPENDIX: t
:CUSTOM_ID: h:2d84e73e-c143-43b5-b388-a6765da974ea
:END:

#+texinfo: @include doclicense.texi

#+begin_export html
<pre>

                GNU Free Documentation License
                 Version 1.3, 3 November 2008


 Copyright (C) 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
     <https://fsf.org/>
 Everyone is permitted to copy and distribute verbatim copies
 of this license document, but changing it is not allowed.

0. PREAMBLE

The purpose of this License is to make a manual, textbook, or other
functional and useful document "free" in the sense of freedom: to
assure everyone the effective freedom to copy and redistribute it,
with or without modifying it, either commercially or noncommercially.
Secondarily, this License preserves for the author and publisher a way
to get credit for their work, while not being considered responsible
for modifications made by others.

This License is a kind of "copyleft", which means that derivative
works of the document must themselves be free in the same sense.  It
complements the GNU General Public License, which is a copyleft
license designed for free software.

We have designed this License in order to use it for manuals for free
software, because free software needs free documentation: a free
program should come with manuals providing the same freedoms that the
software does.  But this License is not limited to software manuals;
it can be used for any textual work, regardless of subject matter or
whether it is published as a printed book.  We recommend this License
principally for works whose purpose is instruction or reference.


1. APPLICABILITY AND DEFINITIONS

This License applies to any manual or other work, in any medium, that
contains a notice placed by the copyright holder saying it can be
distributed under the terms of this License.  Such a notice grants a
world-wide, royalty-free license, unlimited in duration, to use that
work under the conditions stated herein.  The "Document", below,
refers to any such manual or work.  Any member of the public is a
licensee, and is addressed as "you".  You accept the license if you
copy, modify or distribute the work in a way requiring permission
under copyright law.

A "Modified Version" of the Document means any work containing the
Document or a portion of it, either copied verbatim, or with
modifications and/or translated into another language.

A "Secondary Section" is a named appendix or a front-matter section of
the Document that deals exclusively with the relationship of the
publishers or authors of the Document to the Document's overall
subject (or to related matters) and contains nothing that could fall
directly within that overall subject.  (Thus, if the Document is in
part a textbook of mathematics, a Secondary Section may not explain
any mathematics.)  The relationship could be a matter of historical
connection with the subject or with related matters, or of legal,
commercial, philosophical, ethical or political position regarding
them.

The "Invariant Sections" are certain Secondary Sections whose titles
are designated, as being those of Invariant Sections, in the notice
that says that the Document is released under this License.  If a
section does not fit the above definition of Secondary then it is not
allowed to be designated as Invariant.  The Document may contain zero
Invariant Sections.  If the Document does not identify any Invariant
Sections then there are none.

The "Cover Texts" are certain short passages of text that are listed,
as Front-Cover Texts or Back-Cover Texts, in the notice that says that
the Document is released under this License.  A Front-Cover Text may
be at most 5 words, and a Back-Cover Text may be at most 25 words.

A "Transparent" copy of the Document means a machine-readable copy,
represented in a format whose specification is available to the
general public, that is suitable for revising the document
straightforwardly with generic text editors or (for images composed of
pixels) generic paint programs or (for drawings) some widely available
drawing editor, and that is suitable for input to text formatters or
for automatic translation to a variety of formats suitable for input
to text formatters.  A copy made in an otherwise Transparent file
format whose markup, or absence of markup, has been arranged to thwart
or discourage subsequent modification by readers is not Transparent.
An image format is not Transparent if used for any substantial amount
of text.  A copy that is not "Transparent" is called "Opaque".

Examples of suitable formats for Transparent copies include plain
ASCII without markup, Texinfo input format, LaTeX input format, SGML
or XML using a publicly available DTD, and standard-conforming simple
HTML, PostScript or PDF designed for human modification.  Examples of
transparent image formats include PNG, XCF and JPG.  Opaque formats
include proprietary formats that can be read and edited only by
proprietary word processors, SGML or XML for which the DTD and/or
processing tools are not generally available, and the
machine-generated HTML, PostScript or PDF produced by some word
processors for output purposes only.

The "Title Page" means, for a printed book, the title page itself,
plus such following pages as are needed to hold, legibly, the material
this License requires to appear in the title page.  For works in
formats which do not have any title page as such, "Title Page" means
the text near the most prominent appearance of the work's title,
preceding the beginning of the body of the text.

The "publisher" means any person or entity that distributes copies of
the Document to the public.

A section "Entitled XYZ" means a named subunit of the Document whose
title either is precisely XYZ or contains XYZ in parentheses following
text that translates XYZ in another language.  (Here XYZ stands for a
specific section name mentioned below, such as "Acknowledgements",
"Dedications", "Endorsements", or "History".)  To "Preserve the Title"
of such a section when you modify the Document means that it remains a
section "Entitled XYZ" according to this definition.

The Document may include Warranty Disclaimers next to the notice which
states that this License applies to the Document.  These Warranty
Disclaimers are considered to be included by reference in this
License, but only as regards disclaiming warranties: any other
implication that these Warranty Disclaimers may have is void and has
no effect on the meaning of this License.

2. VERBATIM COPYING

You may copy and distribute the Document in any medium, either
commercially or noncommercially, provided that this License, the
copyright notices, and the license notice saying this License applies
to the Document are reproduced in all copies, and that you add no
other conditions whatsoever to those of this License.  You may not use
technical measures to obstruct or control the reading or further
copying of the copies you make or distribute.  However, you may accept
compensation in exchange for copies.  If you distribute a large enough
number of copies you must also follow the conditions in section 3.

You may also lend copies, under the same conditions stated above, and
you may publicly display copies.


3. COPYING IN QUANTITY

If you publish printed copies (or copies in media that commonly have
printed covers) of the Document, numbering more than 100, and the
Document's license notice requires Cover Texts, you must enclose the
copies in covers that carry, clearly and legibly, all these Cover
Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on
the back cover.  Both covers must also clearly and legibly identify
you as the publisher of these copies.  The front cover must present
the full title with all words of the title equally prominent and
visible.  You may add other material on the covers in addition.
Copying with changes limited to the covers, as long as they preserve
the title of the Document and satisfy these conditions, can be treated
as verbatim copying in other respects.

If the required texts for either cover are too voluminous to fit
legibly, you should put the first ones listed (as many as fit
reasonably) on the actual cover, and continue the rest onto adjacent
pages.

If you publish or distribute Opaque copies of the Document numbering
more than 100, you must either include a machine-readable Transparent
copy along with each Opaque copy, or state in or with each Opaque copy
a computer-network location from which the general network-using
public has access to download using public-standard network protocols
a complete Transparent copy of the Document, free of added material.
If you use the latter option, you must take reasonably prudent steps,
when you begin distribution of Opaque copies in quantity, to ensure
that this Transparent copy will remain thus accessible at the stated
location until at least one year after the last time you distribute an
Opaque copy (directly or through your agents or retailers) of that
edition to the public.

It is requested, but not required, that you contact the authors of the
Document well before redistributing any large number of copies, to
give them a chance to provide you with an updated version of the
Document.


4. MODIFICATIONS

You may copy and distribute a Modified Version of the Document under
the conditions of sections 2 and 3 above, provided that you release
the Modified Version under precisely this License, with the Modified
Version filling the role of the Document, thus licensing distribution
and modification of the Modified Version to whoever possesses a copy
of it.  In addition, you must do these things in the Modified Version:

A. Use in the Title Page (and on the covers, if any) a title distinct
   from that of the Document, and from those of previous versions
   (which should, if there were any, be listed in the History section
   of the Document).  You may use the same title as a previous version
   if the original publisher of that version gives permission.
B. List on the Title Page, as authors, one or more persons or entities
   responsible for authorship of the modifications in the Modified
   Version, together with at least five of the principal authors of the
   Document (all of its principal authors, if it has fewer than five),
   unless they release you from this requirement.
C. State on the Title page the name of the publisher of the
   Modified Version, as the publisher.
D. Preserve all the copyright notices of the Document.
E. Add an appropriate copyright notice for your modifications
   adjacent to the other copyright notices.
F. Include, immediately after the copyright notices, a license notice
   giving the public permission to use the Modified Version under the
   terms of this License, in the form shown in the Addendum below.
G. Preserve in that license notice the full lists of Invariant Sections
   and required Cover Texts given in the Document's license notice.
H. Include an unaltered copy of this License.
I. Preserve the section Entitled "History", Preserve its Title, and add
   to it an item stating at least the title, year, new authors, and
   publisher of the Modified Version as given on the Title Page.  If
   there is no section Entitled "History" in the Document, create one
   stating the title, year, authors, and publisher of the Document as
   given on its Title Page, then add an item describing the Modified
   Version as stated in the previous sentence.
J. Preserve the network location, if any, given in the Document for
   public access to a Transparent copy of the Document, and likewise
   the network locations given in the Document for previous versions
   it was based on.  These may be placed in the "History" section.
   You may omit a network location for a work that was published at
   least four years before the Document itself, or if the original
   publisher of the version it refers to gives permission.
K. For any section Entitled "Acknowledgements" or "Dedications",
   Preserve the Title of the section, and preserve in the section all
   the substance and tone of each of the contributor acknowledgements
   and/or dedications given therein.
L. Preserve all the Invariant Sections of the Document,
   unaltered in their text and in their titles.  Section numbers
   or the equivalent are not considered part of the section titles.
M. Delete any section Entitled "Endorsements".  Such a section
   may not be included in the Modified Version.
N. Do not retitle any existing section to be Entitled "Endorsements"
   or to conflict in title with any Invariant Section.
O. Preserve any Warranty Disclaimers.

If the Modified Version includes new front-matter sections or
appendices that qualify as Secondary Sections and contain no material
copied from the Document, you may at your option designate some or all
of these sections as invariant.  To do this, add their titles to the
list of Invariant Sections in the Modified Version's license notice.
These titles must be distinct from any other section titles.

You may add a section Entitled "Endorsements", provided it contains
nothing but endorsements of your Modified Version by various
parties--for example, statements of peer review or that the text has
been approved by an organization as the authoritative definition of a
standard.

You may add a passage of up to five words as a Front-Cover Text, and a
passage of up to 25 words as a Back-Cover Text, to the end of the list
of Cover Texts in the Modified Version.  Only one passage of
Front-Cover Text and one of Back-Cover Text may be added by (or
through arrangements made by) any one entity.  If the Document already
includes a cover text for the same cover, previously added by you or
by arrangement made by the same entity you are acting on behalf of,
you may not add another; but you may replace the old one, on explicit
permission from the previous publisher that added the old one.

The author(s) and publisher(s) of the Document do not by this License
give permission to use their names for publicity for or to assert or
imply endorsement of any Modified Version.


5. COMBINING DOCUMENTS

You may combine the Document with other documents released under this
License, under the terms defined in section 4 above for modified
versions, provided that you include in the combination all of the
Invariant Sections of all of the original documents, unmodified, and
list them all as Invariant Sections of your combined work in its
license notice, and that you preserve all their Warranty Disclaimers.

The combined work need only contain one copy of this License, and
multiple identical Invariant Sections may be replaced with a single
copy.  If there are multiple Invariant Sections with the same name but
different contents, make the title of each such section unique by
adding at the end of it, in parentheses, the name of the original
author or publisher of that section if known, or else a unique number.
Make the same adjustment to the section titles in the list of
Invariant Sections in the license notice of the combined work.

In the combination, you must combine any sections Entitled "History"
in the various original documents, forming one section Entitled
"History"; likewise combine any sections Entitled "Acknowledgements",
and any sections Entitled "Dedications".  You must delete all sections
Entitled "Endorsements".


6. COLLECTIONS OF DOCUMENTS

You may make a collection consisting of the Document and other
documents released under this License, and replace the individual
copies of this License in the various documents with a single copy
that is included in the collection, provided that you follow the rules
of this License for verbatim copying of each of the documents in all
other respects.

You may extract a single document from such a collection, and
distribute it individually under this License, provided you insert a
copy of this License into the extracted document, and follow this
License in all other respects regarding verbatim copying of that
document.


7. AGGREGATION WITH INDEPENDENT WORKS

A compilation of the Document or its derivatives with other separate
and independent documents or works, in or on a volume of a storage or
distribution medium, is called an "aggregate" if the copyright
resulting from the compilation is not used to limit the legal rights
of the compilation's users beyond what the individual works permit.
When the Document is included in an aggregate, this License does not
apply to the other works in the aggregate which are not themselves
derivative works of the Document.

If the Cover Text requirement of section 3 is applicable to these
copies of the Document, then if the Document is less than one half of
the entire aggregate, the Document's Cover Texts may be placed on
covers that bracket the Document within the aggregate, or the
electronic equivalent of covers if the Document is in electronic form.
Otherwise they must appear on printed covers that bracket the whole
aggregate.


8. TRANSLATION

Translation is considered a kind of modification, so you may
distribute translations of the Document under the terms of section 4.
Replacing Invariant Sections with translations requires special
permission from their copyright holders, but you may include
translations of some or all Invariant Sections in addition to the
original versions of these Invariant Sections.  You may include a
translation of this License, and all the license notices in the
Document, and any Warranty Disclaimers, provided that you also include
the original English version of this License and the original versions
of those notices and disclaimers.  In case of a disagreement between
the translation and the original version of this License or a notice
or disclaimer, the original version will prevail.

If a section in the Document is Entitled "Acknowledgements",
"Dedications", or "History", the requirement (section 4) to Preserve
its Title (section 1) will typically require changing the actual
title.


9. TERMINATION

You may not copy, modify, sublicense, or distribute the Document
except as expressly provided under this License.  Any attempt
otherwise to copy, modify, sublicense, or distribute it is void, and
will automatically terminate your rights under this License.

However, if you cease all violation of this License, then your license
from a particular copyright holder is reinstated (a) provisionally,
unless and until the copyright holder explicitly and finally
terminates your license, and (b) permanently, if the copyright holder
fails to notify you of the violation by some reasonable means prior to
60 days after the cessation.

Moreover, your license from a particular copyright holder is
reinstated permanently if the copyright holder notifies you of the
violation by some reasonable means, this is the first time you have
received notice of violation of this License (for any work) from that
copyright holder, and you cure the violation prior to 30 days after
your receipt of the notice.

Termination of your rights under this section does not terminate the
licenses of parties who have received copies or rights from you under
this License.  If your rights have been terminated and not permanently
reinstated, receipt of a copy of some or all of the same material does
not give you any rights to use it.


10. FUTURE REVISIONS OF THIS LICENSE

The Free Software Foundation may publish new, revised versions of the
GNU Free Documentation License from time to time.  Such new versions
will be similar in spirit to the present version, but may differ in
detail to address new problems or concerns.  See
https://www.gnu.org/licenses/.

Each version of the License is given a distinguishing version number.
If the Document specifies that a particular numbered version of this
License "or any later version" applies to it, you have the option of
following the terms and conditions either of that specified version or
of any later version that has been published (not as a draft) by the
Free Software Foundation.  If the Document does not specify a version
number of this License, you may choose any version ever published (not
as a draft) by the Free Software Foundation.  If the Document
specifies that a proxy can decide which future versions of this
License can be used, that proxy's public statement of acceptance of a
version permanently authorizes you to choose that version for the
Document.

11. RELICENSING

"Massive Multiauthor Collaboration Site" (or "MMC Site") means any
World Wide Web server that publishes copyrightable works and also
provides prominent facilities for anybody to edit those works.  A
public wiki that anybody can edit is an example of such a server.  A
"Massive Multiauthor Collaboration" (or "MMC") contained in the site
means any set of copyrightable works thus published on the MMC site.

"CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0
license published by Creative Commons Corporation, a not-for-profit
corporation with a principal place of business in San Francisco,
California, as well as future copyleft versions of that license
published by that same organization.

"Incorporate" means to publish or republish a Document, in whole or in
part, as part of another Document.

An MMC is "eligible for relicensing" if it is licensed under this
License, and if all works that were first published under this License
somewhere other than this MMC, and subsequently incorporated in whole or
in part into the MMC, (1) had no cover texts or invariant sections, and
(2) were thus incorporated prior to November 1, 2008.

The operator of an MMC Site may republish an MMC contained in the site
under CC-BY-SA on the same site at any time before August 1, 2009,
provided the MMC is eligible for relicensing.


ADDENDUM: How to use this License for your documents

To use this License in a document you have written, include a copy of
the License in the document and put the following copyright and
license notices just after the title page:

    Copyright (c)  YEAR  YOUR NAME.
    Permission is granted to copy, distribute and/or modify this document
    under the terms of the GNU Free Documentation License, Version 1.3
    or any later version published by the Free Software Foundation;
    with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
    A copy of the license is included in the section entitled "GNU
    Free Documentation License".

If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts,
replace the "with...Texts." line with this:

    with the Invariant Sections being LIST THEIR TITLES, with the
    Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.

If you have Invariant Sections without Cover Texts, or some other
combination of the three, merge those two alternatives to suit the
situation.

If your document contains nontrivial examples of program code, we
recommend releasing these examples in parallel under your choice of
free software license, such as the GNU General Public License,
to permit their use in free software.
</pre>
#+end_export

#+html: <!--

* Indices
:PROPERTIES:
:CUSTOM_ID: h:dd530040-de9d-4f2b-8dfd-d8b8f14c058e
:END:

** Function index
:PROPERTIES:
:INDEX: fn
:CUSTOM_ID: h:317b8c20-6dc1-4390-a20a-d01d75a48ccb
:END:

** Variable index
:PROPERTIES:
:INDEX: vr
:CUSTOM_ID: h:2f69d4fe-0804-4f7f-aa57-4e03e7f20d98
:END:

** Concept index
:PROPERTIES:
:INDEX: cp
:CUSTOM_ID: h:10365e44-2fc0-4b66-a613-682fea09ee68
:END:

#+html: -->