Clinical Document Architecture (CDA) is an XML-based, electronic standard used for clinical document exchange that was developed by Health Level Seven (HL7). greenCDA is a simplified version of CDA that maintains the full utility of the CDA standard. The greenCDA schema aims to have a shorter learning curve while still delivering valid CDA documents while also enabling a person with basic XML knowledge to create “green” instances.
greenCDA bases its simplicity on plainly defined XML data elements, assigning Business Names that are intuitive and easy-to-understand. It also tries to ensure that all documents can be processed using only XML 1.0 + namespaces. greenCDA utilizes elements instead of attributes where possible. Attributes are often difficult to read and maintain, and XML best-practices recommend the use of elements for data as implemented by greenCDA. This use of elements flattens and simplifies the overall hierarchy.
Other greenCDA simplifications include straightforward datatypes over complex datatypes; concrete datatypes instead of xsi:type; and choice constructs where multiple datatypes are allowed. Also XHTML is used for markup of greenCDA narrative text, which is easier to read and more readily refactored to display on web-pages.
A core requirement of greenCDA is that all greenCDA modules, while simplified in design and complexity, must be transformable to the full CDA. A user may chose to accept the greenCDA.xml and utilize it as-is along with the greenCDA.xsd schema. But if a normative CDA is required, an XSLT transform file (greenCDA.xslt) can be used to transform the greenCDA into a normative “full” CDA. Because static value sets can be stored in the schema or provided by the transform, the greenCDA.xml can be kept as simple as possible. And in cases where the narrative text is derived (entry/@typeCode=”DRIV”), it can be completely left out of the greenCDA and simply derived during the transformation process of a full CDA.
CCD (Continuity of Care Document), an ANSI standard approved in 2007, is built on CDA elements by using a detailed set of constraints. CCD can be a constraint on a greenCDA or full CDA. More information about CCD can be found in our CCD white paper. HL7 announced the upcoming release of greenCDA on February 21, 2011. More information about greenCDA can be found at the HL7.org web-site.
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