Requirements-Value Sets

A value set is a collection of codes from one or more code systems. The definition of the value set may be either an enumeration (extensional) or an expression (intentional)

Value Set

Requirement	Value sets must be able to be identified in a globally unique way.
Rationale	Value sets need to be explicitly referenced in static models, implementation guides and context bindings. This can only occur if they're uniquely identified with no possibility of confusion
Methodology	mif-vocabulary-model.xsd/ValueSet/@id
OMG Mapping	Tagged value of a ValueSet stereotype.

Requirement	Value sets must be able to be given a human-readable label
Rationale	Value sets need to be talked about and understood by human beings and globally unique identifiers aren't terribly useful for humans
Methodology	mif-vocabulary-model.xsd/ValueSet/@name
OMG Mapping	The usual name of a named element in UML.

Requirement	Some value sets need to be able to be marked as "unchangable"
Rationale	With some value sets, there's an identified purpose for the value set and the definition can change over time, so long as the revised set of codes still reflects the original purpose. However, for other value sets, there is no clearly expressible purpose. There is simply an arbitrary set of codes. Anyone who wants that particular arbitrary set can reference the value set. Because the defining characteristic of the value set is the codes themselves, it is not safe for the definition of the value set to ever be revised. As well, those who reference the value set need to have confidence that it's not going to change.
Methodology	mif-vocabulary-model.xsd/ValueSet/@isImmutable
OMG Mapping	Tagged value of a ValueSet stereotype.

Requirement	Value sets must be able to be uniquely identified
Rationale	Value sets need to be explicitly referenced in static models, implementation guides and context bindings. This can only occur if they're uniquely identified.
Methodology	mif-vocabulary-model.xsd/ValueSet/@id
OMG Mapping	Tagged value of a ValueSet stereotype.

Requirement	There's a need to understand the intended purpose of a value set
Rationale	Value sets can be constructed for different reasons. When choosing a value set, it's useful to know why the value set exists. As well, the purpose of the value set can impact what codes are exposed within the value set. For example, in analysis value sets, "abstract" codes would be returned, while they would not normally be part of a value set used for exchange or as a pick-list.
Methodology	analysis: The value set is intended to provide a list of concepts that is definitional in some way. E.g. "Symptoms of dementia". exchange: The value set is intended to identify an allowed set of codes that may be persisted or transmitted. pick-list: The value set is intended to identify a set of displayed values to be exposed to a user from which they can select one or more concepts.
MIF	mif-vocabulary-model.xsd/ValueSetVersion/@use
OMG Mapping	Tagged value of a ValueSet stereotype.

Requirement	Value sets need to be able to track statuses over time.
Rationale	Like other vocabulary objects, Value sets can be draft, active, deprecated or even retired. In some cases, they even get resurrected. Users need to know what the status of a concept domain is right now as well as what it was at times in the past.
MIF	mif-vocabulary-model.xsd/ValueSet/statusInfo
OMG Mapping	Tagged value of a ValueSet stereotype.

Value Set Version

Requirement	Value sets must support multiple versions over time
Rationale	The content of many value sets needs to change over time. Perhaps codes need to be added or removed from an enumeration, or perhaps an expression needs to be tweaked based on changes to one of the referenced code systems
MIF	mif-vocabulary-model.xsd/ValueSetVersion
OMG Mapping	This could also potentially be handled by MOF versioning.

Requirement	Value set versions must be identifiable. Value set versions must also identify the time they were created
Rationale	When binding a value set, sometimes there's a need to bind a specific version (so there's tighter control over the specific set of codes chosen). When a specific version is not chosen, there's a need to know what version of a value set was in effect at a particular time. Usually a date suffices. However, some value sets are revised multiple times a day and therefore time may also be required
MIF	mif-vocabulary-model.xsd/ValueSetVersion/@versionDate mif-vocabulary-model.xsd/ValueSetVersion/@versionTime
OMG Mapping	This could also potentially be handled by MOF versioning.

Requirement	Value set versions must be able to be associated with properties from their respective code systems.
Rationale	Some properties, such as formal naming properties, need to be associated with value sets that make use of codes from a code system rather than just the codes from the code system themselves.
MIF	mif-vocabulary-model.xsd/ValueSetVersion/associatedConceptProperty
OMG Mapping	It seems this could be supported by tagged values on a stereotype. However, it is unclear why it is associated with a version rather than directly with the value set.

Requirement	Value set versions must define the set of codes they contain either by enumeration or expression
Rationale	That's the primary purpose of a value set :>
Methodology	Value Set Content
MIF	mif-vocabulary-model.xsd/ValueSetVersion/content
OMG Mapping	A value set that is an enumeration can be handled as a stereotyped UML enumeration. A stereotype that is an expression can be handled as a stereotyped data type with the expression in an associated constraint.

Requirement	Value set versions must be able to provide examples of the codes included within the value set
Rationale	The full set of codes in a value set may number in the 100s or 1000s, far too many to reasonably publish. However, having some indication of the sorts of codes included in a value set is important for understanding the value set and necessary for publishing.
MIF	mif-vocabulary-model.xsd/ValueSetVersion/enumeratedContent
OMG Mapping	A tagged value of a ValueSet stereotype that contains a set of sample instances. (This would only be useful for the case when the value set is given by an expression not by a small, explicit enumeration. In the latter case, the complete set of values would be given by the enumeration literals.)