The HL7 Clinical Document Architecture (CDA) is a document markup standard that specifies the structure and semantics of "clinical documents" for the purpose of exchange.

The current version is known as Release 2 and has the following key characteristics:

• CDA documents are encoded in XML. 
• CDA documents derive their machine processable meaning from the HL7 Reference Information Model (RIM) and use the HL7 Version 3 Data Types.
• The CDA specification is richly expressive and flexible. Document-level, section-level and entry-level templates can be used to constrain the generic CDA specification

Thus, documents based on the CDA R2 specification could be either uncontrolled or controlled in the sense described in Standards Classification