Section 4.6. Enabling Versioned Views considered the value of views of individual database tables. The objective of these views was to facilitate access to a range of useful snapshot and delta views. This section introduces the idea of defining composite views that access interrelated sets of data from different release files. The objective of composite views is to make it easier to access appropriate sets of data.

Apart from the concept identifier, the concept table contains no useful human-readable data about a concept. Therefore, simply selecting data from a snapshot view of the concept table is unlikely to be useful.

To display appropriate human-readable information about a concept information is required from two other tables:

  • The human-readable information about a concept is in the description table or view (e.g. snap_description)
  • Information about which descriptions are preferred or acceptable in given language data is in a language refset table or view (e.g. snap_refset_language).

To display human-readable information about the way a concept is defined data is required from three other tables:

  • The defining relationships are in the relationships table or view (e.g. snap_relationship)
  • Human-readable display of the type and value specified in the relationship requires data from the description table or view (e.g. snap_description)
  • Information about which descriptions are preferred or acceptable in given language data is in a language refset table or view (e.g. snap_refset_language).


The following subsections describe some general characteristics of composite views and introduce some of the composite views included in the SNOMED CT example database.