Friday, January 22, 2010

Implementation Technology Specifications

I met today with the Implementation Technology Specification (ITS) Workgroup to discuss ITS issues related to the HL7 CDA Standard, both for the current CDA Release 2.0 and also CDA R3 currently being developed by the HL7 Structured Documents Workgroup.

One Schema to Rule them All and Bind them
In the first meeting, we discussed Grahame Grieve's proposal for a RIM-based ITS.  This ITS is, I think, rather important for the representation of HL7 Version 3 messages and documents.  The RIM-based ITS uses the HL7 RIM semantics to produce a single schema that describes a RIM-based artifact (message or document).  The beauty of the RIM-based ITS is that it contains something on the order of 50 or so classes. This is a volume that can be readily taught to engineers, rather than the current collection of 50 domains, 1000+ interactions, and I'm certain an order of magnitude more "clones"1. It also associates the RIM class names with the XML element names so that element names are meaningful.   This eliminates much of the cognitive dissonance caused by the current XML ITS.

The ITS workgroup agreed to develop a scope statement for a project that would develop this as an HL7 standard.

The μ ITS 
The idea of the μ ITS is spawned by two other initiatives, as I stated in a previous post:  hData and the Green CDA work of Alschuler and Associates and Bob Dolin.  Taking the ideas of these two projects a step further, I came up with the concept of the μ ITS.  We discussed this idea in the ITS meeting along with the other two ideas, and came to the conclusion that they address three areas of concern that have some overlap and some differences.  The ITS work group agreed to develop a scope statement to be reviewed an sent up the chain.  I'm writing the first draft with collaborators from MITRE (developers of hData).  Structured Documents agreed to write a scope statement for development of a proof of concept for the Green CDA using the CCD templates, and to work with the ITS and Implementation and Conformance work groups on it.

Now, here's how I think this all breaks down:
The μ ITS is a collection of principles describing a micro-ITS, its required properties, artifacts and deliverables.  hData is a transport mechanism that uses one or more micro-ITS implementations to exchange information.  Green CDA is an instance of a micro-ITS.  A fourth project is a μ-Processor.  The μ-Processor takes as input a collection of business rules governing an exchange described in a controlled fashion, some business names, and an algorithm for unifying them.  As output it produces a micro-ITS.  The specification of the μ ITS will be informed by the development of a prototype μ-Processor.


Finally, there is one last ITS I'd like to mention in passing.  It is derived from the work of the HL7 Clinical Decision Support work group on the URL-based implementation guide for the Context Aware Information Retrieval (Infobutton).  That specification is a RESTful query for information pertinent to a clinical act in a particular context.  It occurs to me that several HL7 interactions, some of which are queries, and others of which are retrieval operations, could benefit from a similar specification.  The RESTful Query ITS presents a set of rules by which an HL7 message that retrieves a resource is converted from the HL7 Model presentation (an R-MIM) into an HTTP GET request.  Interactions which are appropriately designed can readily and quickly implemented using these rules.  I believe that the URL-based Infobutton Specification is an implementation that could very much inform this sort of ITS.  One of the things that would likely go into an RQ ITS is the application of business names to an HL7 model artifact.  The business names would then become the parameters of the query.  

Today was a very productive day.  I was able to help coordinate the efforts of two different committees trying to reach similar goals.  Throughout there was a spirit of collaboration and even more importantly, the willingness to look at innovation in HL7.   Not everyone feels comfortable with these directions.  There are some slippery slopes that we could slide down with no way back up.  A few pitons have been driven in to rope us off, and even those don't seem all that substantial.  However, we do have to listen to our customers, and these initiatives are certainly attempts to meet their needs.

I'm not sure that Green CDA is something that HL7 would have considered a few years ago, nor do I believe that we would have had the necessary experience to approach it as we are today.  The same is true of the μ ITS.  I'm hopeful that we'll see significant progress on both of these initiatives in Rio in May, and look forward to playing with some of the ideas that we've been exploring this week.  Tomorrow I'll tell you about another toy that I plan on playing with in the coming months ... Template Registries.


P.S. I hadn't realized that I had created a triple pun with the name μ ITS. 
  1. The Greek letter MU is one character before the Greek letter NU, and the the MU ITS is a step back  from the New ITS.  
  2. When translated to its English pronunciation MU is an acronym for Meaningful Use.  
  3. Finally, the μ symbol is used for the metric prefix micro, also meaning small, and a μ ITS is intended to create smaller and simpler messages (this is the one I missed)

1 A clone is a renamed copy of a RIM class that has been restricted by a working group to a subset of the full RIM semantics. The name of the clone in an HL7 message or document appears as the XML Element name but it "carries" no semantics.

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