There are a number of alternative techniques that may be used when exchanging SNOMED CT expressions in messages. These include:
- Placing the full SNOMED CT compositional grammar expression in the relevant code field of the message.
- For example, as noted in section 2.3, the HL7 version 3 CD data type (Release 2) allows the 'code' property to include SNOMED CT expressions (see HL7 TermInfo guide).
- Using an alternative structure for representation of the logical structure of an expression.
- For example an OWL serialization.
- Placing a unique expression identifier in the relevant code field of the message
- This approach requires the use of a shared expression repository enabling the recipient system to look up and resolve this identified to the relevant expression.
- Decomposing the expression into separate codes that can be placed in different fields within the message structure.
- This approach assumes alignment between the message structure and the relevant parts of the SNOMED CT concept model.
Please refer to section 5 of the Record Services Guide for more information on exchanging expressions.