The "everything is a database" took two forms. First, apps had no filesystem available, only a database which they could use as a datastore. It was not a parti

The "everything is a database" took two forms. First, apps had no filesystem available, only a database which they could use as a datastore. It was not a particularly powerful or fancy database, everything had to be done via the C++ API rather than a query language IIRC. But it simplified app development quite a bit and made the apps smaller and more robust. Second, there was a set of common tables available to all apps that provided the basic PIM data, including addresses, calendar, todo, email and notes. This meant that third party apps could safely interoperate with this data alongside the builtin apps and extend functionality.