TMCore is built on relational database technology and exposes a complete relational data model for the topic maps managed by the system. The model consists of a set of views and pre-defined SQL functions which can be used to construct arbitrary queries across all topic map data using any of the SQL constructs supported by the underlying database - this includes statistical functions; data conversion fucntions; full-text query extensions and so on. Unlike the indexes covered in the section called “The Core Indexes”, the relational model also allows multiple topic maps to be queried simultaneously.