• Focus: The general focus of the Value Set as it relates to the intended semantic space. This can be the information about clinical relevancy or the statement about the general focus of the Value Set, such as a description of types of messages, payment options, geographic locations, etc.
• Model Context: A statement that describes how this Value Set is to be used in an artifact.
• Inclusion Criteria: Criteria describing what concepts or codes should be included and why.
• Exclusion Criteria: Criteria describing what concepts or codes should be excluded and why.

The default value is FALSE. Note that the implication is that if this is set to ‘true’, thereafter, the current Value Set Definition version must be the last Value Set Definition allowed. The Immutable Flag tends to be set to ‘TRUE’ in one of two cases:

• Where the Value Set Definition, by the nature of its usage, cannot change (e.g., "all specializations of ACT in ActClassCode")
• Where there's no safe way to express the "Scope" such that someone else could safely make changes to the Value Set Definition.

Source workflow control must guarantee that the same URI always yields the same definition.

human-readable monikers of this Value Set Definition.

a web pointer to where the Value Set Definition may be located.

Word or words that may be used in an information retrieval system to index the contents of the Value Set Definition. The string datatype allows implementers to use strings or coded concepts.

This may be used to surface indexing terms for a search.

The information captured in “Use” can and should include names of programs and/or names of organizational entities that use the value set definitions, including standards that require the value set definition. This is likely to be a “point in

time” view and should not be considered an authoritative listing of all uses of the Value Set. In the USA, the Value Set Expansions created for electronic quality measures (eCQMs) that are a part of the Meaningful Use requirements could implement this as follows:

• User: Measure Steward name; Usage: Measure Identifier & version/Name
• User: Centers for Medicare & Medicaid Services (CMS); Usage: eCQM release identifier.

Content Logical Definition

formal representation used to determine the coded concept contents to be included in the Value Set Expansion Code Set

The Content Logical Definition (CLD) is a formal representation of Value Set content and is intended to be machine processable. It is used to generate the coded content of the Value Set Expansion, i.e., the Value Set Expansion Code Set.

This element uses the ED data type (REFERENCE ED) meaning that the content is structured and that the structure includes an identification of the structure (or the application that must be used to interpret the data). For example, an “HL7 Expression” uses a MIME type of “application/xml”. This flexibility means that subsequent specifications can identify the allowance for additional expression syntaxes.

The HL7 Expression functions are an available syntax for the CLD that is described below, possibly including some recursive elements. Each recursive section is considered a “clause”. The Value Set Definition Version contains a single mandatory Content Logical Definition that describes different types of specifications of content, some of which contain or reference Content Logical Definitions; thus the definition is inherently recursive. The list of functions is described in Section 6.

the release and/or usability state

The state that represents the current state of the Value Set Definition in the context of the Value Set creation and release process.

The Activity Status should track the status with regards to the Value Sets availability for use in a publishing environment context. Changes to this element should never result in a new Value Set Definition Version.

This element has the following allowed values:

• Preliminary: State during which time the Value Set Definition version is being drafted and is not available for use. The element Workflow Status Descripition will carry additional information regarding pre-Active state.
• Active: State during which the Value Set Definition version is available for use. The Activity Status Date associated with this status is known as the “Effective Date”.
• Inactive: State indicating that the Value Set Definition version is no longer available for use in creating new content. The Activity Status Date associated with this status is known as the “Expiration Date”.
• Deleted: State intended to be used to remove a Value Set Definition from use and view in a repository and is only possible if the Value Set was never Active (i.e., can only transition from Preliminary).

Since activity status is only represented here in Value Set Definition Version information and is a required element, then any Value Set Definition that does not have this is not valid. Furthermore, a Value Set Definition may have more than one Value Set Definition Version with any of the status states noted. Given that this can lead to overlapping Active definitions, external governance must be available to either restrict the allowed overlap or resolve overlap if usage does not specify a particular Value Set Definition Version.

the date when the associated Value Set Definition Version activity status is in effect.

When the Activity Status is set to “Active”, the Activity Status Date defines the Effective Date which is the date-time the Value Set Definition Version becomes active.

When the Activity Status is set to “Inactive”, the Activity Status Date is the date-time when the Value Set Definition version becomes Inactive. This cycle may happen multiple times. The specified time is expected to be one second after midnight UTC of the Activity Status Date. The date may be in the future.

It is strongly encouraged that the Activity Status be set such that no more than one Value Set Definition Version for a single Value Set Identifier can have an Activity Status of ACTIVE at the same time within a single realm. In cases where this is not true, evaluation of the alignment of a Value Set Expansion Code Set to a specific Value Set Definition, as referenced in a CD, will be problematic.

Changes to this element should never result in a new Value Set Definition Version.

the state of development of the Value Set Definition while in a single Activity Status.

Workflow Status Description is used to represent details of the Value Set Definition development process. The development of a Value Set Definition often follows a formal workflow process from initiation to completion and this element carries the state variable for this state machine. The assumption is that when first created, a Value Set Definition would have a workflow state of Draft. Additional workflow states may be used.

The values that are traditionally used for this element while the Value Set Definition has an Activity Status of Preliminary are assumed to include phrases that capture various stages in review and approval. It is expected that this would be used to manage maintenance activities, but that a terminology service would not be expected to expose this information. Different services might adopt different workflow status description values reflecting their local practices.

As an example, the US Value Set Authority Center (VSAC) uses the following workflow status descriptions. The Activity Status is “Preliminary” (see Activity Status) for all these workflow status descriptions:

• “Draft” – The initial Value Set Definition creation status. An author can make changes to the Value Set Definition only while the definition is in this status.
• “Proposed” – Once an author has completed editing, the Value Set Definition is submitted for review by a Value Set steward. The submission changes the Value Set Definition to this status and editing can no longer occur.
• “Approved” – When the Steward completes the review and approves the Value Set Definition. This status is for Value Set Definitions that have successfully completed a review process but are not yet set to be published.
• “Ready to Publish” – This status occurs when the steward sets a Publication Date that defines when the Value Set Definition version is to become ACTIVE (Activity Status = ACTIVE). The VSAC Value Set Definition version is in this status from the time the publication date is set until the publication time. VSAC Value Set Definition versions are published at 00:01 (one minute after midnight) of the publish date morning (Eastern Time) and the earliest a Value Set Definition version can be published is the next day’s morning.

VSAC allows all Value Set Definition workflow status descriptions to be changed back to the prior status as long as the Value Set Definition has not been “Published” (Activity Status = ACTIVE).

A Value Set Definition version can only have one workflow status description at any time. There may be additional states defined by different developers. This is an optional element because the

use of Activity Status “Preliminary” may be sufficient for some implementations. Changes to this element should never result in a new Value Set Definition version.

This is a textual description of the organizational entity responsible for the content and maintenance.

1..1

the entity or set of entities that create and may modify the Value Set Definition content.

The name of a group or an individual.

This can be any combination of groups or individuals. When known and actively maintained, this should be populated. The information included about the Author may include contact information.

Changes to this element should never result in a new Value Set Definition Version.

characterization of the Value Set Definition

user-defined descriptive phrase meant to characterize the content logical definition (CLD.)

The following descriptive words have traditionally been used to describe the CLD in HL7 standards. Other phrases may be of use for some users.

• Extensional: the CLD is a simple list of individually specified concepts that uses no relationships or other attributes to determine the Value Set Expansion Code Set.
• Grouping: the CLD is restricted to a UNION of one or more other Value Set Definition references.
• Intensional: the CLD is an algorithm that, when executed by a machine (or interpreted by a human being), yields a set of concepts.

the Code System(s) identifiers explicitly referenced by the Value Set Definition’s Content Logical Definition.

An exhaustive list of all Code Systems referenced in the Content Logical Definition.

This list of Code System Identifiers should be derived from the Content Logical Definition to ensure that it is accurate. When the Content Logical Definition does not specify any content types based on Code Systems, this is not populated. It is possible that a Code System will be in the CLD but not generate a concept in the Value Set Expansion Code Set if codes specified in the CLD are inactive or if an expression does not identify any codes; therefore, this may list Code Systems that are not resident in a specific Value Set Expansion Code Set.

uri

0..*

1..1

date and time when an element was changed in some way.

This should be captured precisely enough to prevent confusion. In most cases, a date may work, but particularly volatile cases may require greater precision such as down to the second.

identifier for the changes for each revision

Unique identifier for the change captured in the revision history.

This may be used to disambiguate multiple changes and revisions that all carry the same timestamp, such as those done for publishing reasons. It may be best if this is a GUID.