3/18/19990© 1999, Health Level Seven, Inc. Introduction: Vocabulary domains Marital Status –single (never married) –married –divorced –separated “Vocabulary” to distinguish from “Subject Domains” in the RIM Why Vocabulary Domains? –Increase interoperability –Sharing of data (clinical care, outcomes, research) –Sharing of decision logic

3/18/19991© 1999, Health Level Seven, Inc. Vocabulary domain “The set of all concepts that can be taken as valid values in an instance of a coded field or attribute.” Concept - “A unit of thought constituted through abstraction on the basis of characteristics common to a set of objects.” ISO 1087 Each concept in the domain can be represented using a specific vocabulary/terminology

3/18/19992© 1999, Health Level Seven, Inc. Each coded attribute has a domain specification Class: Patient Description: A person who may receive, is receiving, or has received healthcare services. Associations is_a_role_of (1,1) :: Person is_source_for (0,n) :: Specimen_sample Attributes birth_order_number birth_dttm (from Person) gender_cd

3/18/19993© 1999, Health Level Seven, Inc. Vocabulary Domain Specification One and only one for each coded RIM attribute General form: – Currently two types of domain qualifiers –Extensibility (Extensibility) CNE - Coded No Exceptions CWE - Coded With Exceptions –Realm (RealmOfUse) Universal USA? Europe? Others

3/18/19994© 1999, Health Level Seven, Inc. Specialization of Domains Used in specifying message –MIM, MET, CMET, HMD, Clinical Templates(?) Example: –MyGender = (“Gender:USA:HL7” - “Other:USA:HL7-001”) General Form –“value set name” “value set name” Value set name –“Domain name:Realm:Terminology” Allowed set operators –“+” Union (  ) –“-” Difference (sometimes represented as “\”) –“*” Intersection (  )

3/18/19995© 1999, Health Level Seven, Inc. Validating Specifications and Constraints Validation can be time and resource intensive May want to do selective validiation –During testing and debugging –During conformance testing –During the creation of each message –During the decoding of each message –Only on some fields –Only when errors occur –Or all of the above

3/18/19996© 1999, Health Level Seven, Inc. General process of maintaining domains Follow pattern of RIM harmonization Vocabulary TC appoints facilitators Message development TCs have stewardship –Ultimate authority for domain contents –Follow RIM harmonization rules Vocabulary Facilitators –Insure that good vocabulary practices are followed –Actual maintenance of domain specification database –Submit new concepts to vocabulary providers All vocabulary/terminology providers can provide mappings to HL7 domains

3/18/19997© 1999, Health Level Seven, Inc. Domain specification table maintenance (plan) Available on HL7 web site –All members can read tables Edit Permissions table –who can edit which domains –vocabulary co-chairs maintain permissions table Assigned persons make edits (proposed status) Entries reviewed by Vocab Review Committee Reports presented to RIM harmonization process Approved changes reflected by status chanages HL7 standard versions synch’ed with edit versions

3/18/19998© 1999, Health Level Seven, Inc. Local Vocabulary Use Can only be used with qualifier Strength:CWE The complete domain is a union of standard domain plus local concepts (as a union of the two) Rules –Local concept can not replace standard concept –Local code system names must start with “99” –Local codes should be submitted to HL7 for inclusion in standard domain and forwarded to terminology developers

The Domain Specification Database

3/18/199910© 1999, Health Level Seven, Inc. The domain specification database This is only the first version. There will be future enhancements to domain specifications and to the table design Requirements: (UML model not shown) –Unique, non-sense identifier –Unique textual name –Description/definition –Edit note –Version tracking –Can be specific to a realm of use –Each “leaf” set is from a single vocabulary –Domains can be recursively defined –Set notation will be used to describe relationships

3/18/199911© 1999, Health Level Seven, Inc. Domain Specification Database Tables Value Set Definition Table Version Tracking Table Edit Permissions Table (not shown) Value Set Relationship Table Source Vocabulary Representation Table Observation Identifier to Value Set Linking Table

3/18/199912© 1999, Health Level Seven, Inc. Value Set Definition Table

3/18/199913© 1999, Health Level Seven, Inc. Value Set Definition Table (content 1) A single row is a value set –Each row gets a unique HL7 Value Set Id –The primary key consists of Domain Name, Realm, Code System The union of all value sets with the same Domain Name is a domain

3/18/199914© 1999, Health Level Seven, Inc. Value Set Definition Table (content 2) Two kinds of mutually exclusive domains –Domains maintained by HL7 –Domains maintained by external terminology providers An HL7 maintained domain can not have value sets defined by reference to an external terminology

3/18/199915© 1999, Health Level Seven, Inc. Value Set Definition Table (content 3) Expression contains the information that can be used to resolve the value set to its individual elements The expression would be sent to a terminology service The semantics of the expression are specific to the terminology service

3/18/199916© 1999, Health Level Seven, Inc. Value Set Definition Table - Version Tracking A value set gets a Vin number when it first becomes a part of the table A value set gets a Vout number when it becomes inactive A value set with a blank Vout is currently active

3/18/199917© 1999, Health Level Seven, Inc. Version Tracking Table A new version get created each time there is a new editting session The version number becomes part of each domain specification table as edit are made A permissions table (not shown) controls who can edit which value sets

3/18/199918© 1999, Health Level Seven, Inc. Value Set Relationship Table Value Set Name and Concept Name are only shown for purposes of illustration Operator can be Include or Exclude Generality says whether to include the node itself in the value set

3/18/199919© 1999, Health Level Seven, Inc. Source Vocabulary Representation Table Based on example from Wayne Tracy HL7 Concept ID asserts HL7’s view of synonyms HL7 Concept ID could be replaced by universal concept identifier (UMLS CUI?) Supports multiple languages

3/18/199920© 1999, Health Level Seven, Inc. Observation Id to Value Set Linking Table Used to connect value sets to observation identifiers when used in name-value pairs like an OBX segment LOINC gives only examples, and is not prescriptive Allows for strong constraints when OBX like structures are used in messages

3/18/199921© 1999, Health Level Seven, Inc. Using the Domain Specification Database Look in Value Set Definition Table –Use domain name, realm, and code system –Find and remember the Expression Pass the Expression to a terminology server (TQS) Knowledge of how to resolve HL7 Value Sets to individual elements is available in the Value Set Relationship Table and the Source Vocabulary Representation Table Knowledge of how to resolve external Value Sets is the responsibility of the terminology provider