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Compared to HL7 Value Set
The term "value set," , when discussed in the context of HL7 can be somewhat ambiguous. There are at least three related artifacts that are sometimes called "value sets", including 1) a definition or algorithm that, when interpreted, produces a set of concept codes, 2) the actual set of concept codes that result from the execution of a definition or algorithm, and 3) a subset of this set of concept codes coupled with appropriate designations and identifying information. For this reason, the LexEVS model uses the names "value set definition", "value set resolution" and "pick list definition", "pick list resolution" respectively to represent the three different senses of "value set" described above.
Value Set Definition logical
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Model
Value Set Definition logical
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MOdel description
Value Set Definition
A definition of a given value set. A value set definition can be a simple description with no associated value set entries, or it can consist of one or more definitionEntries that resolve to an enumerated list of entityCodes when applied to one or more codingScheme versions.
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A Value Set Definition can have 0 to any number of DefinitionEntry. Each DefinitionEntry basically is used to define the rules as to what entityCode(s) to be included or removed from the value set. There are four different kind of rules that can be set :
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- CodingSchemeReference
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- ValueSetDefinitionReference
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- EntityReference
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- PropertyReference
These references are described in the following sections. Each DefinitionEntry can contain one and only one of these references. Each DefinitionEntry will be processed independent of the other DefinitionEntries. They will be processed sequentially according to the ruleOrder and will be merged to the final set based on the operator specified.
There are three different type of operator that can used :
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- ADD - The processed DefinitionEntry will be merged to the final set using the 'AND'. This will include only the entity codes that are both in the value set and the DefinitionEntry. (logical AND)
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- OR - The processed DefinitionEntry will be merged to the final set using the 'OR'. This will add the set of entityCodes described by the current DefinitionEntry to the value set. (logical OR)
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- SUBTRACT - The processed DefinitionEntry will be merged to the final set using the 'SUBTRACT'. This will subtract (remove) the set of entityCodes described by the current DefinitionEntity to the value set. (logical NAND)
Attributes of Definition Entry
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Attributes of Entity Reference
The following are attributes of entity reference.
- entityCode: The entity code being referenced.
- entityCodeNamespace: Local identifier of the namespace of the entityCode. entityCodeNamespace must match a local id of a supportedNamespace in the corresponding mappings section. If omitted, the URI of the defaultCodingScheme will be used as the URI of the entity code.
- leafOnly: If true and referenceAssociation is supplied and referenceAssociation is defined as transitive, include all entity codes that are "leaves" in transitive closure of referenceAssociation as applied to entity code. If referenceAssociation is not supplied and transtiveClosure is 'false', this flag will be ignored. Default: false
- referenceAssociation: The local identifier of an association that appears in the native relations collection in the default coding scheme. This association is used to describe a set of entity codes. If absent, only the entityCode itself is included in this definition.
- targetToSource: If true and referenceAssociation is supplied, navigate from entityCode as the association target to the corresponding sources. If transitiveClosure is true and the referenceAssociation is transitive, include all the ancestors in the list rather than just the direct "parents" (sources).
- transitiveClosure: If true and referenceAssociation is supplied and referenceAssociation is defined as transitive, include all entity codes that belong to transitive closure of referenceAssociation as applied to entity code. Default: false
Property Reference
A reference to a propertyName or propertyValue and matchAlgoritm to use.
Attributes of Property Reference
The following are attributes of property reference.
- codingScheme: The local identifier of the codingScheme that this propertyReference will be resolved against. codingScheme must match a local id of a supportedCodingscheme in the corresponding mappings section.
- propertyName: The local identifier to be used to restrict the entities to have property with this name. Must match a local id of a supportedProperty in the corresponding mappings section.
- propertyMatchValue: Value to be used to restrict entity property. matchAlgorithm can be used in conjunction to get matching entity properties.
Property Match Value
Property match value to be used to restrict entity property. matchAlgorithm can be used in conjunction to get matching entity properties.
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Attributes of Definition Operator
The following are attributes of Definition Operator.
- OR: Add the set of entityCodes described by the currentEntity to the value set. (logical OR)
- SUBTRACT: Subtract (remove) the set of entityCodes described by the currentEntity to the value set. (logical NAND)
- AND: Only include the entity codes that are both in the value set and the definition entry. (logical AND)
Possible
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Forms of Value Set Definitions
The following are possible forms of value set definitions.
- Definition containing just the reference to Code System - includes all the concept codes in the referencing code system.
- Definition containing just the reference to other Value Set Definition -includes all the concept codes defined in the referencing Value Set Definition.
- Definition containing reference to Code System plus concept codes - includes individual concept codes defined in the definition from the referencing code system.
- Definition containing reference to Code System plus concept codes plus relationship plus additional rules (leaf only, immediate children, matching property name/value etc) - includes concept codes from the referencing code system that satisfies the rule set defined in the definition.
- Combination of any of the above with OR/AND/SUBTRACT operations.
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Value Set Definition Resolution
The following is information about value set definition resolutions.
- A value set definition has to be made against a specific version of a code system.
- But it doesn't have to be resolved against the same version.
- Even a simple list (a, b, c, d) needs to be resolved as, at some future date, "c" might be retired.
- Resolution does not create static artifact.
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