Additional fields loaded along with the Thesaurus

This field takes a value of "Y" or "N", indicating whether a term is valid for use in a field linked to the Thesaurus.

This field takes a value of "Y" or "N", indicating whether a term is to be Used For (i.e. in place of) other terms. If other terms in the Thesaurus have a Use reference set to this term, this field should be set to "Y".

This field stores a string of IRNs indicating the hierarchy of terms above this term. For example, consider the following Thesaurus (with the IRNs enclosed in brackets):

Top Term (1)

   Second Level Term 1 (2)

      Third Level Term 1 (5)

   Second Level Term 2 (3)

      Third Level Term 1 (6)

         Fourth Level Term 1 (7)

   Second Level Term 3 (4)

The internal hierarchies for each of the terms would be as follows:

Top Term (1) - [blank]

   Second Level Term 1 (2) - 1

      Third Level Term 1 (5) - 1:2

   Second Level Term 2 (3) - 1

      Third Level Term 1 (6) - 1:3

         Fourth Level Term 1 (7) - 1:3:6

   Second Level Term 3 (4) - 1

The hierarchy is made up by joining the IRNs from each of the broader terms and separating them with a colon. It is important that the IRNs are recorded in their hierarchical order because this field is used by the sub-tree restriction code to determine whether a particular term falls into a sub-tree of allowed values.

It is a nested table because both single- and multi-hierarchy thesauri may have multiple broader terms. Each broader term hierarchy must be recorded in this field. This means that if a term has two broader terms and one of those also has two broader terms, three internal hierarchies will need to be recorded in this field. This is because this term may be arrived at by traversing three different sub-trees.