Requirements-Context Binding

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Context binding is based on the concept of Concept Domains and Binding Realms. Initial model designs reference abstract concept domains that avoid referencing particular sets of codes. Specific sets of codes are then chosen within the context of a particular binding realm. For example, the set of codes used for diagnosis in the U.S. for human patients might be different than that chosen for veterinary patients in Canada.

MIF Reference: mif-model-vocabulary.xsd/ContextBinding

Requirement HL7 Standards must be able to be constructed with coded elements that are not constrained to a specific set of codes, while still constraining the 'types' of codes that are considered appropriate and ensuring that consistent codes are used for a given concept across parts of a specification. For example, in a universal pharmacy ballot, it may be appropriate to constrain an attribute to codes of type "Orderable Drug" even though it is not possible to identify the specific codes due to varying regulatory requirements in different countries.
  • There are variations in healthcare across countries, cultures, medical discipline (e.g. internal medicine vs. psychiatry), type of patient (e.g. human vs. veterinary or pediatric vs. geriatric)
  • There is still a need to provide guidance about what types of codes are appropriate for a given element
  • Failure to use consistent codes within different parts of a specification (e.g. one set of codes for create messages and a different set for update messages) would lead to interoperability issues

Requirement It must be possible to take a given abstract content definition (Concept Domain) and identify the specific set of codes with specific conformance expectations (Value Set Conformance) that can be used in a given context (Binding Realm)
Rationale This is a definition of what the Context Binding methodology is.

Value Set Conformance

  • mif-model-vocabulary.xsd/ContextBinding/@conceptDomain
  • mif-model-vocabulary.xsd/ContextBinding/@bindingRealmName
  • mif-model-vocabulary.xsd/ContextBinding/boundValueSet
OMG Presuming that concept domains, binding realms and value sets are all represented in UML as classifiers, then a context binding can be represented as a ternary association between them (probably stereotyped, per below).

Requirement Context Bindings may change over time
  • New terminologies are constantly in development. A terminology selected for a given use today may not be considered appropriate 3 years from now. For example, migrating from an ICD10 set of codes to a SNOMED CT set of codes when the jurisdiction is ready for the migration.
Methodology Each vocabulary binding has a start date and may have an end date. (Bindings should not change frequently enough to necessitate a time component)
  • mif-model-vocabulary.xsd/ContextBinding/@effectiveDate
  • mif-model-vocabulary.xsd/ContextBinding/@expiryDate
OMG Tagged values of a stereotype on the association representing the context binding.

Requirement Multiple independent sets of codes may be simultaneously considered 'valid' for a single concept domain within a specified context.
Supplemental Requirement The set of codes used to cover a concept space by a given implementation must not have more than one code drawn from more than one code system to represent a given concept
  • With the exception of synonyms defined within a single code system, no code from two independent code system has exactly the same meaning
  • Multiple codes with similar but not exactly equivalent meaning cause issues for mapping and equivalence testing
  • In some cases, it will not be possible for a particular jurisdiction to 'land' on a single set of codes for political reasons. (E.g. a recognized need to use SNOMED CT but a large legacy base of ICD10)
  • When transitioning from one agreed set of codes to a new set of codes, there may be a period of time where both sets of codes are considered acceptable
  • mif-model-vocabulary.xsd/ContextBinding/@bindingPriority
OMG The binding priority can be represented as a tagged value of the stereotype on the association representing the context binding.