CDA R3 avoid xsi:type

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Submitted by: Rick Geimer	Revision date: August 31, 2009
Submitted date: August 31, 2009	Change request ID: <<Change Request ID>>

Issue

Requiring the use of the xsi:type attribute is problematic. First, it binds CDA to the XML Schema language (other schema languages, like RelaxNG, do not support xsi:type), and also many XML tools to not support this XML Schema specific attribute.

Recommendation

• Create clones of the <value/> element (inside an observation) that are pre-bound to specific datatypes, i.e. <physicalQuantity/> would be pre-defined as a PQ.

Rationale

Creating named clones for each datatype allowed in CDA would limit our dependence on the XML Schema language, and also improve tool compatibility.

For example, In the following observation:

    <observation classCode="OBS" moodCode="EVN">
        
        <statusCode code="completed"/>
        <effectiveTime value="200004071430"/>
        <value xsi:type="PQ" value="1.77" unit="m"/>
    </observation>

you could replace

    <value xsi:type="PQ" value="1.77" unit="m"/>

with

    <physicalQuantity value="1.77" unit="m"/>

For more reasons why the use of xsi:type is often frowned upon, refer to Norm's blog entry on the subject: http://norman.walsh.name/2004/01/29/trainwreck.

Resolution

March 23, 2010: This is an ITS and data types issue. Opposed: 0; Abstain: 0; In favor: 6.