4. CAPS™ layer 0: the database

CAPS™ "Layer 0", outside of CAPS™ proper, can be any enterprise-level RDBMS (Relational Database Management System). The RDBMS's functionality must include such features as transactions, views, outer joins, and the like. Layer 0 is also informally known as the "database layer".

The development of CAPS™ has taken place using PostgreSQL (with some specific attention also given to Oracle), without exploiting special, non-portable features found in PostgreSQL only. Special features and quirks specific to each given RDBMS can be encapsulated into a thin, well specified "portability layer". As a consequence, future addition of other RDBMS engines of comparable functionality, if and when AB Strakt's partners and customers require it, will be feasible.

However, please note that CAPS™ defines its own DB schema. Integrating CAPS™ with other existing applications that use the same DB engine, but with their own schemas, is a task similar to that of other integrations between CAPS™ and existing applications. There is no way to make CAPS™ just use a pre-existing relational DB schema. Therefore, normally, no special advantage is gained by having CAPS™ Layer 0 share a particular DB engine with other applications. Many of the beneficial system characteristics we shall examine in the following depend on the crucial design choice of having CAPS™ define and use its own DB schema.