The general pattern is used to represent expression logic throughout the resources in the Clinical Reasoning module and allows expression logic to be represented at different levels:
– Unstructured – The logic in this case can be communicated using natural language without the expectation that it is computable. This information is useful for communicating the intended dynamic semantics to environments that do not support computable evaluation.
– Structured – The logic is specified as a computable expression in a formal language. This information is useful for communicating the logic to environments that are expected to support the computation.
– Mixed – The logic in this case is communicated using both a natural language description, as well as a computable expression in a formal language. This information is useful for communicating to environments that may support the computation as well as to environments that do not, or to environments that support the computation but desire human-readable information to more easily understand the logic.
For example, the Dynamic Value element of the Activity Definition and Plan Definition resources contains these three elements – description, language, and expression – directly. However, for resources that do not define these elements, extensions are provided to enable expression information to be associated with any FHIR resource.