RIM Maintenance and Tooling Documentation

Introduction

To quote the HL7 standard "Core Principle and Properties of V3 Models":

The essential feature of HL7 Version 3 is that its specifications (standards) SHALL be based on a set of common models, and that, to the extent possible, these models will be based on the object modeling facilities of the Unified Modeling Language (UML). In HL7 Version 3, the information models for the specifications (standards) are based on three "core" models that are published as individual specifications but have been developed and maintained though careful collaboration and coordination within the HL7 community. These models are:

• HL7 Reference Information Model (RIM) is an "information model" covering all information that must be communicated in support of health care ...

• HL7 Abstract Data Types Model is a robust specification of data types ...

• HL7 Vocabulary Model is a set of HL7-defined and maintained Concept Domains, Code Systems and Value Sets ...

To this end, development of the HL7 Reference Information Model (RIM) was started in 1996, and has been a continuing process since. To date, HL7 has released over 60 RIM versions, including three "normative" releases. This document lays out the processes and tooling used to maintain the RIM.

Harmonization and Publication

The primary process for RIM development and maintenance process known as the Vocabulary and RIM Harmonization Process. This process was initiated as RIM Harmonization and extended when Vocabulary specifications became a key, formal part of V3 specifications. This process is documented elsewhere.

Publication of the RIM occurs in several forms:

• As a formal document for balloting and inclusion in V3 Normative Editions.

• As a set of formal definitions (represented in Model Interchange Format (MIF) files or data bases) and released for use with tools developed by HL7 and others. These are released under the "Design Repository Project" on Gforge. Prior to May 2011, the primary representation was an an HL7 Design Repository in Access. With the release of this updated process, the primary representations become MIF "definition files" for the RIM and Vocabulary.

• A formal RIM "model package" release that inlcudes modeling tool files, documentation of Harmonization changes, graphics, etc.

Prior Maintenance and Objectives

As the first version 3 methodology was defined, an Access "Design Repository" database was designed to represent all of the HL7 modeling artifacts in Access tables. Thus, there were tables for RIM classes, attributes, etc. Moreover, for each of the major elements model, a set of unique identifiers (GUID) was defined, and recorded along with data showing which version of the RIM a particular element became effective, and/or was dropped.

Not only were the data recorded in the primary design repository tables, but they were also transferred to an archive of model elements that allowed reconstruction of any single RIM version. With these data, it is possible to track the evolution of a particular attribute from its initial introduction into the RIM, through a variety of updates, to its final version, or perhaps its elimination from the RIM altogether.

The actual modeling the RIM depended upon in early-release UML modeling tool produced by Rational Software. HL7-specific properties were added to this modeling tool to allow documentation of the assigned each identifiers, vocabulary constraints, etc. The maintenance tooling included software that used programming interfaces (API) to both the modeling program and the Access repository to automate the processes of loading models to the data base, comparing the content, documenting differences, and updating the unique identifiers as recorded in the modeling tool, if necessary.

The development of new tools used this suite of capabilities as its primary set of requirements.

RIM Maintenance Process

The Vocabulary and RIM Harmonization Process for RIM development remains unchanged.

Modeling Tool

The primary modeling is now performed with IBM's Rational Software Architect - a UML tool implemented in the Eclipse environment and using the Eclipse modeling framework. This model is then "exported" using the UML XMI format.

RIM Archive

Representation of individual RIM models is expressed as a "mif:staticModel" from MIF 2.1.6, The representation of the RIM Archive data is contained in a "mif:package" element whose "content" is made up of the most recent RIM "staticModel", in its entirety, and a set of historic "mif:staticModel"s that reflect the changes, version-to-version as the models evolved. Transforms are provided for updating the archive to accommodate a new RIM release, and for extracting any particular RIM from the archive.

RIM Distribution

RIM distribution continues in the three primary groups as outlined under publication in the Introduction section above, although the specific content of each changes, as outlined in the following tooling discussion.

RIM Maintenance Tooling

Base Modeler

Model Elements Used

As noted above, the base modeling tool is Rational Software Architect. Within the RIM, the following model elements from the UML suite are used:

• Package to aggregate classes into "subject areas"
• Class
• Attribute
• Primitive Type to capture the assignment of a particular HL7 data type. The data types are not explicitly modeled in the RIM. The Primitive Type "name" establishes the binding to an HL7 data type.
• Bidirectional Association to capture the relationships, names and multiplicities between classes.
• Generalization to establish inheritance relationships between classes.
• State Machine made up of
  • State
    • Initial State
    • Final State
  • Transition - triggered by a named Signal Event

HL7 Profile

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