I just drew the spectrum. It exists now. SQLite is a file format. You can read/write SQLite databases without the SQLite library. You can write your own custom

I just drew the spectrum. It exists now. SQLite is a file format. You can read/write SQLite databases without the SQLite library. You can write your own custom reader/writer/creator. You don't have to use SQL. You don't have to be ACID compliant. I can make for you right now a SQLite database that did not touch any SQLite software, put data into it and you can open it with another piece of software that implements the SQLite file format specification. Likewise, you can use the SQLite library software to create a SQLite database file, put data into it, and I can read it/update it using any other software that implements the SQLite file format specification. The SQLite library offers some very very basic features, such as ACID compliance, and so on, but those are not part of or guarantees of the file format or the database files. The software that you write that implements the SQLite file format specification does not have to do any of these things to work with or produce a valid SQLite file. An RDBMS is a kind of DBMS for managing relational databases and providing access to the databases (for example users and permissions). Modern RDBMSs offer extensive features (look at an Oracle or MSSQL Server spec sheet) that are not even hinted at with the SQLite library software. This is because SQLite is not an RDBMS, it's a file format.