The C154 HITSP Data Dictionary document executes what I consider to be best practice in this arena. Each row in the data dictionary includes four items, which are described below1:
- DATA ELEMENT IDENTIFIER
Each data element has an identifier that uniquely identifies it. The first part of the identifier is assigned based upon the module where it is found. The second part of the identifier uniquely identifies the element within the module. As new data elements are created, they are added to the end of the data module. The data element identifiers are persistent and will not be changed or reused between versions of HITSP specifications.
- DATA ELEMENT NAME
Each data element has a name that briefly describes the content and purpose of the data element. Data element names may be changed between versions of HITSP specifications to better describe the content and purpose.
- DATA ELEMENT DEFINITION
Each HITSP data element has a definition that is intended to precisely describe the purpose and structure of the data element independent from the standards that it may be mapped to. This independence allows HITSP data elements to be mapped to data elements using a variety of standards. The concise definition and mapping to the standards data element also supports harmonization of data across exchanges using different standards. The definition should describe the data element with sufficient enough detail to clearly indicate the purpose and content of the data element.
- DATA ELEMENT CONSTRAINTS
In some cases, the data element will have additional restrictions limiting the values that can be communicated within it. HITSP may apply restrictions to a data element when it is communicated. These restrictions could be with regard to its precision, the units, and the range of legal values that may be transmitted or other restrictions as necessary. These will be described in or referred to by this column.
This column defines universal constraints that apply to data elements regardless of the Base Standard (i.e. HL7 CDA, HL7 V2 messages, NCPDP, etc.) allowing for harmonized constraints across the various Base Standards. Additional data element constraints may also be defined in the CDA-specific sections of this document (2.2.x), or in HITSP Components, Transactions, Transaction Packages or Interoperability Specifications.
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