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Analysis of CDA R2 testing tools - most requirements are neither tested nor respected.

Publication date: Feb 13, 2015

During the recent IHIC conference IHE Europe published an analysis that shows serious weaknesses in the current CDA validation tools.

When it comes to the validation of CDA documents one can distinguish a number of steps which should form the basis for a full validation of a CDA document: any CDA document has to be

  1. well-formed XML,
  2. valid with respect to the published CDA schema,
  3. conform with all requirements of the CDA abstract HL7v3 model - inclusive of all of the CDA requirements that aren't expressed as part of the schema, because the schema language is simply not expressive enough to deal with all of the requirements as expressed in the abstract model,
  4. conform to the requirements as expressed in a CDA Implementation Guides - more often than not a process where multiple templates (as defined by the implementation guide) have to be validated.

The object of the analysis by IHE Europe (Abderrazek Boufahja, Eric Poiseau, Guillaume Thomazon and Anne-Gaëlle Bergé) was to examine to which degree the existing CDA Tools as well as existing national/regional CDA projects meet the requirements of the 3rd validation step. The authors identified 160 requirements which should be tested by any CDA validation tool. Once they had a list of requirements they tested existing CDA validation tools to see whether those would detect the issues in question, and they tested example messages defined by national/regional projects to see whether those projects used a strong enough validation process.

Boufahja presenting during the IHIC 2015

Even if the list of 160 requirements should be incomplete, or if some of those requirements are erroneous, the results of the analysis is a clear indication that more work is needed by all parties concerned:

  • The CDA tools that were tested are: Trifolia, MDHT, Eclipse Instance Editor, Art-Decor, the NIST validation tool, and the IHE Gazelle ObjectsChecker tool. If we exclude the new IHE Gazelle ObjectsChecker tool (which does catch almost all of the 160 requirements) the old Eclipse Instance Editor (no updates since 2011 - no longer available for download) performed best, the remaining tools have a worse performance. Now some will argue (as I do) that the aim of some of these tools (e.g. Trifolia, Art-Decor) has never been to deal with the 3rd validation step, but only to focus on the 4th validation step (templates). Still, the validation strength of MDHT and the NIST validation Tool should be improved upon. Note that the Everest toolkit hasn't been tested - the tool was unknown to IHE Europe at the time of the analysis.
  • They also tested message examples from 10 national/regional projects, the average number of errors found in the example CDA documents ranged between 2 and 44. So there are projects out there where (on average) a CDA document has 44 known issues. It seems the various CDA projects also have to beef up their testing process. The list of most frequent errors can be found in the paper, they are more or less the same as the ones we found in an earlier similar study in 2008 - which just goes to show that projects should move away from XML based validation and should instead focus on model based validation.

The actual paper (published under the CC-BY-NC-ND license) can be found on the EJBI website (special 2015 issue related to IHIC), a scanned copy (PDF) can be found on the Ringholm website.

In my opinion this was the most interesting paper presented at the IHIC meeting in Prague earlier this week - toolkit developers as well as national/regional CDA projects should learn its lessons and beef up their support for stricter CDA validation.


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