...

If Deltashell opens an old project it creates a session for that version of the DB. After that all objects are migrated to a new session with the current configuration. Then when the project is saved the database is in a new format.

How does DS know which mapping to use?

Each project database contains a table with plugin version information with which the db was written. The version is the same as used for the plugin assembly. This could look like this:

Now development continues and breaking changes occur. This could look like this :