By design, SimDB "is a" TAP service. It is a TAP service in that it presumes that metadata is stored in a relational database and ADQL queries can be sent to it to query about its contents. It specialises TAP in that it defines what the data models is according to which the database is designed. I.e. all tables/columns etc are fully specified and all SimDB implementations must folow that data model.

We use TAP in full generality rather than a predefined parameterised query language because it offers greatest flexibility. Targeted clients can always wrap the ADQL interface with parametrised forms if they so desire.

In a later stages/versions we may consider allowing other query langugages, for example XQuery. In version 1.0 we want to apply the existing IVOA query language.

The SimDB/TAP_SCHEMA is derived form the SimDB data model described [[][elsewhere]]. It is derived following a prescribed set of object-relational mapping rules.