The The SNOMED CT compositional grammarCompositional Grammar allows allows
to to be represented as a text string that can be carried in messages. For example, in
HL7 version version 3 messages SNOMED CT expressions can be placed in the 'code' property of the ConceptDescriptor (CD) data type (Release 2). The compositional grammar described in this document is intended to replace the
mechanism that formerly was in the CD data type (Release 1), and which was removed in
Release 22.
In September 2009, the HL7 Version the
Version 3 Standard "Data Types - Abstract Specification,
Release 22" was published for its fourth normative membership ballot. This revised standard defined what can be carried in the 'code' property of the CD data type as shown below in Table 1.
...
Table 1. Definition of the 'code' property of the Concept Descriptor (CD) data type from HL7 Data Types Release 2 |
|
ST ST.SIMPLE
Definition: The plain code symbol defined by the code system, |
concept expression in a syntax defined by the code system which describes the |
concept. (emphasis added) If provided, the code SHALL be an exact match to a plain code symbol |
or expression defined or expression defined by the codeSystem. If the codeSystem defines a code |
or expression that or expression that includes whitespace, the code SHALL include the whitespace. |
An expressionAn expression can only be used where the codeSystem either defines |
an expressionan expression syntax, or there is a generally accepted syntax for the codeSystem. (emphasis added) |
The syntax described in this document is intended to satisfy the need for a "syntax defined by the code system" as stated above, when the "code system" is SNOMED CT. For specific guidance on using SNOMED CT Compositional Grammar in the CD data type (Release 2), please refer to Appendix B.4 of "HL7 Version 3 Implementation Guide: TermInfo – Using SNOMED CT in CDA R2 Models, Release 1" [2].