From the September 27, 1999 draft document: "Clinical documents are defined as legally authenticated (attested or signed) and persistent entries into a patient record. The architecture specifies a document markup format which enables documents to be transferred on-line or stored in files on off-line media. While this statement of scope hinges on the legally-authenticated record, it is understood that the PRA applies equally to such documents before authentication is affixed and to authenticated documents that have been superceded. The HL7 Document is intended to be the basic unit of a document-oriented Electronic Patient Record (EPR). In the document-oriented patient record, whether computer- or paper-based, the patient's medical record is represented as a collection of documents. The Patient Record Architecture (PRA) does not specify the management of such documents, only the documents themselves. Reports such as billing abstracts, insurance claims, and epidemiological reports as well as the birth-to-death patient record are derived from the basic clinical documents by extraction, copying, linking or combination. This specification does not describe those views, but only the basic record from which those views are created. Those implementing structured document systems for healthcare may choose to adopt PRA DTDs directly into their application or environment. Yet applications and implementations commonly have features and requirements that exceed the definitions of a standard DTD, even PRA DTDs created for specific domains. It is likely that developers will instead implement DTDs tailored to their own requirements that incorporate the shared PRA markup and extend it with local markup. This is normative and desirable because the PRA is predicated on use of XML transformations, allowing vendors and institutions to augment their information to meet their requirements and business rules, and to innovate without either violating standard practice or retarding development. The PRA seeks to standardize the highest level of shared meaning while providing a clean and standard mechanism for expressing meaning that is not shared. Thus it is assumed that most implementations will transform their own tag set into the PRA tag set and where there is no PRA equivalent, will use a tag indicating 'local markup'." [HL7 Document. Patient Record Architecture. DRAFT - Framework Document. September 27, 1999. Kona Editorial Group chartered by HL7 SGML/XML SIG.]
The work is directed toward "exchange of authenticated clinical documents - legally authenticated, persistent entry into the patient record. PRA documents are to be "'human readable'. This principle means that PRA documents are readable using: a) widely-available and commonly deployed XML-aware browsers and b) a generic PRA style sheet written in a standard style sheet language. [They are also to be] 'machine processable - at the highest level of shared semantics."
The PRA envisions a multilevel architecture: "There will be three levels in the PRA architecture. (1) Level One will specify one core document type definition. (2) At Level Two and Level Three, architectural DTDs will differ for different document types and/or domains of clinical practice. (3) Thus, there will be PRA architectural DTDs for Level Two and Level Three document classes such as History & Physical or Discharge Summary."
References:
PRA presentation (PowerPoint). "Atlanta Plenary. Here are the materials for the introduction to XML, Paul V. Biron and Sandy Boyer, instructors, and here are the materials for the introduction to HL7's XML patient Record Architecture, Chris Almy and Liora Alschuler, instructors." [local archive copy]
HL7 Patient Record Architecture Ballot Proposal Package. Presented to the Technical Steering Committee, September 28, 1999. [local archive copy]
HL7-XML Web Site at the Institute for Medical Informatics, University of Giessen.
XML-Schema for HL7, from Giessen. [cache]
[October 18, 2001] "HL7 ebXML Demonstration Overview. Introduction for HL7." By Todd Freter (XML Technology Center, Industry Initiatives, Sun Microsystems, Inc.) October 2, 2001. 17 pages. "Health Level 7 (HL7) is a non-profit consortium dedicated to the development and publication of protocol specifications for application level communications among diverse health data acquisition, processing, and handling systems. This annotated presentation by Todd Freter of the Sun XML Technology Center provides an overview of HL7's ebXML proof-of-concept demonstration. ebXML: [The author describes who launched the ebXML initiative, who is supporting it, and where to go for basic information; presents the five layers of the ebXML e-business framework, starting at the highest level and descending down to the wire-level. It also mentions the technical architecture description and quality review process, which keep the effort honest...; makes the point the ebXML enjoys support and participation from around the globe, and that the effort has garnered several important endorsements.... showsprovides the phases in which ebXML is delivering its work products. In May 2001, ebXML voted to accept all of its specifications either as full specifications or as technical reports to be developed into full specifications. Since then the ongoing work has been divided between the UN and OASIS... It's important to note that the technical effort is also motivated by a desire to enable second- and third-world economies to participate in the internet economy without having to incur the high cost of EDI. To that end, the notion of royalty-free licensing of ebXML specifications is a key consideration..." [cache]
[October 16, 2000] Clinical Document Architecture (CDA). A recent announcement from Health Level Seven reports on the progress of the Clinical Document Architecture (CDA): "Health Level Seven, Inc. (HL7) successfully balloted what it believes to be the first XML-based standard for healthcare -- the Clinical Document Architecture (CDA). The CDA, which was until recently known as the Patient Record Architecture (PRA), provides an exchange model for clinical documents (such as discharge summaries and progress notes) -- and brings the healthcare industry closer to the realization of an electronic medical record. The CDA Standard is expected to be published as an ANSI approved standard by the end of the year. By leveraging the use of XML, the HL7 Reference Information Model (RIM) and coded vocabularies, the CDA makes documents both machine-readable-so they are easily parsed and processed electronically-and human-readable-so they can be easily retrieved and used by the people that need them. CDA documents can be displayed using XML-aware Web browsers or wireless applications such as cell phones, as shown by Nokia at the HIMSS 2000 demonstration. The CDA is only the first example of HL7's commitment to the advancement of XML-based e-healthcare technologies within the clinical, patient care domain. Along with the CDA, HL7 is developing XML-based Version 3 messages. These Version 3 messages enhance the usability of HL7 by offering greater precision and less optionality, conformance profiles that will help guarantee compliance, coded attributes linked to standard vocabularies, and an explicit, comprehensive, and open information model-the HL7 RIM. All this, packaged in a standardized XML syntax for ease of interoperability. In 1999, HL7 also successfully balloted a recommendation for sending V2.3.1 messages using XML encoding. In 2001, HL7 will ballot, as a normative standard, a methodology for producing HL7 approved DTDs for Version 2.4 and previous versions. Said Stan Huff, chair of the HL7 board of directors: 'XML is an encoding that complements the semantic content provided by the HL7 RIM, allowing users to exploit all the possibilities of the Internet. The extensibility inherent in XML is resulting in an explosion of schemas and DTDs from diverse sources, which actually decreases the ability to provide plug and play applications. The development of a model-based, standardized and industry-accepted application of XML, as provided by HL7, will help decrease the cost of integration, and improve the reliability and consistency of communications between disparate systems and enterprises.' HL7's history with the Web and XML stretches back to the inception of the technologies. The organization is a long-standing and active member of the World Wide Web Consortium-the creators and keepers of XML. It has also exchanged sponsor memberships with OASIS, a non-profit, international consortium that operates XML.org, a global XML industry portal used to collect and distribute XML schemas."
See also: "Template Definition Language (TDL)."
See also: SGML Initiative in Health Care (HL7 Health Level-7 and SGML/XML)
See also: ASTM XML Document Type Definitions (DTDs) for Health Care
