Add initial description for database

README.md

@@ -11,6 +11,7 @@ This document documents the objectives as well as analysis and design for the pr
 - [Background](background.md)
 - [Objective](objective.md)
 - [Use cases](uc.md)
+- [Database](db.md)
 
 -----
 

db.md

@@ -0,0 +1,45 @@
+# Database
+
+To persist the information as specified in [Use Cases][uc.md],
+we need to design an appropriate database accordingly.
+This section discusses the structure for each information.
+
+Due to the target for Android development, SQLite is chosen as the platform's database.
+SQLite is a relational database that has a programming interface in virtually
+any modern programming language.
+On top of that, it is natively supported on both Android and iOS.
+It is also suitable for a custom [application file format][app-format]. In fact,
+Anki used SQLite for its flashcard deck file.
+SQLite supports databases upto [281 terabytes][size], which is more than enough
+for the use case.
+
+[app-format]: https://sqlite.org/appfileformat.html
+[size]: https://sqlite.org/whentouse.html
+
+## Phonology and Phonetics
+### Set of consonants, vowels, tones
+
+The database for this would likely be mostly fixed in number of rows.
+
+- IPA (`TEXT`): The International Phonetic Alphabet representation of the sound.
+- X-SAMPA (`TEXT`): The X-SAMPA equivalent, which allows user to type on a non-IPA keyboard
+- is_used (`BOOLEAN`): Whether the sound is used in the language
+
+## Grammar
+### Inflection
+### Syntax
+## Morphology
+### Affixes
+### Part of Speech
+## Writing system
+### Scripts
+## Vocabulary
+## Others
+
+Not all data can be represented as structured data.
+For example:
+
+- Image
+- Audio
+
+These kinds of data are stored as file blobs in a dedicated SQLite table.