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Structures which propagate context in HL7 models

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HL7 Version 3 includes specific attributes, which indicate whether context propagates across Participation and ActRelationship associations. The rules associated with these attributes determine whether the target Act of an ActRelationship shares the participations and other contextual attributes of the source Act and whether these can be substituted by alternative explicit values within the target Act.

Propagation of context is valuable and in some cases almost essential, as it reduces the need to duplicate contextual information. However, it is not entirely clear whether and if so how this propagation of context applies to coded information in each Act instance. Safe interpretation of clinical information requires a common understanding of where contextual information represented using SNOMED CT if either Act.code or Observation.value propagates to related Acts based on the context propagation rules. For example, several Observations coded using SNOMED CT disorder concepts might be related as component parts of an Organizer labeled with the SNOMED CT code "family history of disorder". If the coded context propagated it might seem to express a family history, if not these might be part of the personal medical history of the subject of record.

The following rules are specified to minimize the risk of ambiguity due to loss of contextual information.

  1. SNOMED CT contextual information SHOULD NOT be assumed to propagate between Acts and SHOULD therefore be restated in each expression.
    • For example, each SNOMED CT expression in a collection of statements representing family history, SHOULD represent the relevant [ 408732007 | subject relationship context ]. This context SHOULD NOT be assumed to propagate from an Organizer (or other containing Act) to its constituent Observations or from one Observation to another.
  2. In specific cases where there is clear advantage is allowing specific aspects of SNOMED CT context to conduct, this behavior SHALL be explicitly documented in a manner that ensures reproducible interpretation.

It is not clear how context conduction is intended to apply to contextual information that is represented in concepts within an Act. If this type of context is assumed to propagate it would mean that the meaning of a single Observation might be fundamentally altered by a related Act (or potentially by a chain of several different related Acts). This type of dependency presents significant risks, since different systems may be unable to reproducibly determine the composite meaning. Therefore, it seems safest to recommend restatement of the essential aspects of context as defined by the SNOMED CT context model rather than permitting this context to conduct.

There may be some specific cases, where a tightly coupled set of Acts are expected to behave as a block with regard to the surrounding context and where some or all aspects of context represented using SNOMED CT also need to be conducted. In these cases the potential for misinterpretation needs to be considered and appropriately documented.