The Reference Information Model (RIM)
The Reference Information Model (RIM) is the cornerstone of the HL7 Version 3 development process. An object model created as part of the Version 3 methodology, the RIM is a large pictorial representation of the clinical data (domains) and identifies the life cycle of events that a message or groups of related messages will carry. It is a shared model between all the domains and as such is the model from which all domains create their messages. Explicitly representing the connections that exist between the information carried in the fields of HL7 messages, the RIM is essential to our ongoing mission of increasing precision and reducing implementation costs.

Templates
An HL7 template is a data structure, based on the HL7 Reference Information Model, and which expresses the data content needed in a specific clinical or administrative context. They are prescribed patterns by which multiple OBX segments may be combined to describe selected, gross observations. Some observations may be quite simple, such as the blood pressure concept in healthcare, which involves a set of expected observations (i.e., systolic, diastolic, patient position, method, etc.)

Other more elaborate diagnostic procedures may involve hundreds of related pieces of information, including anatomy, orientation, sequences of measurements, etc. Templates provide a means of coupling the multiple OBX segments needed to send the observation with separately encapsulated rules for combining/validating them for the particular observation. Based on user need and preference, the template offers the user the advantage of defining the collection of OBX segments needed and the corresponding set of validation rules once, and once, defined, the structure can be used again and again. Since they are based on a specific user's needs/requirements, Templates can be "plug and play" at a given user site.

HL7 approved the formation of the Templates Special Interest Group at its September 2000 meeting. The group will create normative standards for the definition of HL7 templates. These standards will provide that an HL7 template be composed of data structures drawn from the HL7 RIM, that make use of HL7 vocabulary domains.