I agree with Ken that it is challenging situation when it comes to CDA implementation.

A few things that I think worth clarification

- Version numbers
* CDA base specification have two major versions so far, CDA release 1 and CDA release 2
* Data Type versions: HL7 International has two major releases, Data Type release 1 and Data Type release 2, each release with both abstract as well as XML implementation specification to go along
* CDA R1 and R2 both use Data Type release 1, HL7 V3 international release currently uses Data Type release 2, so there is a discrepancy there at international level between V3 messaging and documents
* Pan Canadian Message Standards Data Type (MR data types) is mostly Data Type release 1 but it pre-adopted some Data Type Release 2 stuff
* Consolidated CDA release, regardless of versions (R1.1, R2) are templates based on CDA Release 2, so it uses Data Type Version 1, with SDTC extensions which defines a few more data elements and attribute for CCD document

- Other than a human readable version of pan Canadian header, no other CDA specification in Canada at national level exists today. The adoption of MR2.05 data types for CDA implementation in Canada is in the form of a former SCWG2 decision.

- Data type differences can hinder interoperability between US and CA CDA implementations assuming everyone built according to the CDA specs/decisions in each country. Comparing CDA R2 schema (data type 1) to MR2.05 data type schema, there are some differences, mostly related to mandatoriness and annotations, in Address related elements there was the addition of an optional “code” elements. Also for US vendor who implemented Consolidated CDA, the support for the SDTC extension is required, such extension is not part of pCS date type specification.

- Are there good reasons to use different data types for Canadian CDA from the CDA spec/implementation in U.S? Were there good reasons to use different data types for pan Canadian messaging to begin with?

- CDA header template is a different story as many European countries and Australia have defined their own templates including header templates, it is deemed legit. Do vendors put in effort to support all the different templates for each country or region? It depends on incentives, regulation and/or other drivers…

I met today with OntarioMD and Infoway to chat about the promise of CDA in Ontario. What I heard wasn't promising. I summarized my impressions in a blog post:

http://khstevens.blogspot.ca/2015/05/obstacles-to-cda-adoption-in-ontario.html