Value Set Definition

Value Set Definition with in the LexGrid logical model defines the contents of Value Set. The contents are concept codes defined in referencing Code System. Value Set can contain concept codes from one or more Code Systems.

Compared to ISO 11179 Model

The LexGrid "value set definition" is analogous to the 11179 enumerated conceptual domain. We support the notion of an intrinsically defined enumerated domain, so the 11179 enumerated conceptual domain is really the output of the resolve value set definition function.

Value meanings are identified by entity codes within a given code system. The mapping between permissible values and value meanings is currently accomplished via a mapping association, where we treat the set of permissible values as a "mini code system". An example of how this might work is that HL7 has a set of permissible values of "M", "F", "U", which are in the administrative gender "code system". In the pure HL7 context, these might well map to the equivalent value meanings identified by "M", "F" and "U". If, however, we were using, say, the UMLS as a source of meaning, the same codes would map to the corresponding UMLS CUIs.

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 Model

The following figure shows an overview of the value set definition logical model described in the following section.

This graphic is an overview of the value set definition logical model.

Value Set Definition logical 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.

Attributes of Value Set Definition

The following are attributes of value set definition.

Definition Entry

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 :

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 :

Attributes of Definition Entry

The following attributes of definition entry.

Coding Scheme Reference

A reference to all of the entity codes in a given coding scheme.

Attributes of Coding Scheme Reference

codingScheme: The local identifier of the coding scheme that the entity codes are drawn from . codingSchemeName must match a local id of a supportedCodingScheme in the mappings section.

Value Set References

A reference to the set of codes defined in another value set definition.

Attributes of Value Set Reference

valueSetDefinitionURI: The URI of the value set definition to apply the operator to. This value set may be contained within the local service or may need to be resolved externally.

Entity Reference

A reference to an entityCode and/or one or more entityCodes that have a relationship to the specified entity code.

Attributes of Entity Reference

The following are attributes of entity reference.

Property Reference

A reference to a propertyName or propertyValue and matchAlgoritm to use.

Attributes of Property Reference

The following are attributes of property reference.

Property Match Value

Property match value to be used to restrict entity property. matchAlgorithm can be used in conjunction to get matching entity properties.

Attributes of Property Match Value

matchAlgorithm: Algorithm to be used in conjunction with propertyValue.

Definition Operator

The description of how a given definition entry is applied.

Attributes of Definition Operator

The following are attributes of Definition Operator.

Possible Forms of Value Set Definitions

The following are possible forms of value set definitions.

Definition of the Value Set could be as simple as specifying just individual concept codes or specifying to include all the children of concept 'Body Structure' from Code System 'SNOMED CT' to complex definition containing multiple rule sets.

Examples of Value Set Definitions

Example 1

So we have a Code System "Automobiles" that contains concept codes Domestic Automaker and Automobile. Domestic Automaker contains Ford and General Motors. Autombile contains Truck, Car, and Tires.

We define a Value Set Definition to contain all the concept codes to contain Code System 'Automobiles.

ValueSetDefinition URI : urn:VDexample1
ValueSetDefinition : All Automobiles
defaultcodingcheme: Automobiles

And when this definition is resolved, we will get back all the preferred designations.

This is example 1 as described above.

Example 2

Using the same Code System "Automobiles" if you want to define the same value set definition to include all concept codes except "General Motors" and the children, it can be defined as follows:

ValueSetDefinition URI : urn:VDexample1
ValueSetDefinition : All Automobiles BUT GM
defaultcodingcheme: Automobiles

And when this definition is resolved, we will get back all the preferred designations.

This is example 2 as described above.

Value Set Definition Resolution

The following is information about value set definition resolutions.

Value Set Definition Versions

Value Set Definitions are versioned. The version of Value Set Definition changes when ever the definition is changed, it could be adding or removing Code System reference or changes in the rule set. Value Set authoring services are exposed in CTS 2 implementation of LexEVS. <Link here>

Value Set Services

Visit Value Set Services for detailed Value Set Definition Services documentation.

Value Set GUI

Visit LexEVS 6.0 Value Set GUI for detailed functionality and howto's about using Value Sets developer GUI tool