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glossary-ref

Gloss
tSNOMED
CT
contains hundreds of thousands of glossary-ref
Gloss
tConcepts
and this rich resource is greatly expanded by use of glossary-ref
Gloss
tpostcoordinated
expressions
. In any given situation the range of glossary-ref
Gloss
tConcepts
or glossary-ref
Gloss
texpressions
that are useful, relevant and meaningful is much more limited. This gives rise to a requirement to represent glossary-ref
Gloss
tconstraints
on the content or a particular field in a way that can be interpreted and applied by application software.

The simplest

glossary-ref
Gloss
tconstraint
requirements can be met by specifying the list of valid codes. This requirement is addressed by glossary-ref
Gloss
tsubsets
specified using the glossary-ref
Gloss
tReference
Set
mechanism. In some cases, it is useful to express the range of possible values 'intensionally' by specifying rules rather than by listing every member of the set (e.g. to include all glossary-ref
Gloss
tconcepts
that are glossary-ref
Gloss
tsubtypes
of a specified glossary-ref
Gloss
tconcept
).

The use of

glossary-ref
Gloss
tpostcoordinated
expressions
adds further dimensions to the requirement for glossary-ref
Gloss
tconstraints
. It may be necessary to specify whether all
Glossary ref
postcoordinated
Glossary ref
Gloss
Spacetrue
tpostcoordinated
Gloss
trefinements
of glossary-ref
Gloss
tconcept
are permitted or whether some types of glossary-ref
Gloss
trefinement
are prohibited or required. It may also be necessary to specify whether a glossary-ref
Gloss
tpostcoordinated
expression
that is equivalent to a permitted value is itself permitted.

Requirements for representing

Glossary ref
expression
Glossary ref
Gloss
Spacetrue
texpression
Gloss
tconstraints
are closely related to the requirements for representing glossary-ref
Gloss
tquery
predicates
in queries.