Stylesheet Semantics

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(this is currently a summary of an e-mail discussion)

Suggested clarification for inclusion in CDA R3:

"The use of a particular stylesheet SHALL not add any semantics to the semantics as conveyed in the CDA document. A stylesheet shall only render (extracts of) the semantics as conveyed in the CDA document and not add any semantic data of its own." (we probably need to rephrase the exact wording)

The only safe place to put clincial content is within the CDA document itself.

  1. the stylesheet is (in principle) not part of the (attested) document
  2. a receiving system has no vanilla-CDA-conformance-level obligation to use a supplied stylesheet.

Once there is an obligation (e.g. as stated in an implementation guide) to use a supplied stylesheet then the stylesheet is ipso facto an integral part of the clinical document, and it becomes perfectly reasonable (although discouraged) to add clinical content to a stylesheet.

Problem

I've seen a (beta) implementation of a minimalistic CDA document, sent jointly with a stylesheet. The stylesheet added clinical details (as well as data normally conveyed in the CDA header) to the presentation of the CDA contents.

(ficticious example) All patients in my specilized clinic suffer from disease X, so my stylesheet used for discharge letters will contain that default information, and the CDA document itself doesn't. The stylesheet changes the semantics of the document itself when viewed by a receiver. If the receiver applies a generic CDA stylesheet then a lot less information is available in the CDA document proper.

From CDA R2: Human readability shall not require a sender to transmit a special style sheet along with a CDA document. It must be possible to render all CDA documents with a single style sheet and general-market display tools.

  • A specific implementation guide may mandate the use of a specific stylesheet

Discussion

  • (Frank O) adding semantics to a - normally signed - document by applying special stylesheet is VERY dangerous. Not to say it may impact jurisdiction.
  • the CDA spec (as a universal specification) should not manadate that a certain stylesheet be used. Such a statement could be part of an implementation guide, or of contractual agreements between parties that use/communicate CDA documents, but it is out of scope for the standard spec. Nevertheless, recommendations are in order.
  • (Ann W) IMO the thing to do to cover your concern is to make it clear that the only safe place to put clincial content is within the CDA document itself, because the stylesheet is in principle not part of the (attested) document - and in particular that a receiving system has no vanilla-CDA-conformance-level obligation to use a supplied stylesheet. Once there is an obligation to use a supplied stylesheet then the stylesheet is ipso facto an integral part of the clinical document, and it becomes perfectly reasonable to act as in your example.
  • (Ann W) let me postulate a possible counterexample:
    • A CDA document has been sent and stored in a receiver's repository for some time. During that interval, some new regulation comes into force that stipulates that certain wording (maybe a warning or alert) must be presented to a human reader alongside a certain specific kind of clinical content. Including this wording in a stylesheet for rendering may be a very sensible way to effect the change for existing data, without breaking the integrity or attestation of the original document. It might also have become illegal to transfer the document onward to a third party without the additional content.
    • IMO it would be better to be clear about what is expected good practice, rather than making it a conformance issue. Any standard can be used badly, no matter how closely defined.
  • (Rene) In this case (adding color to the rendered text to highlight values that are below/above reference ranges) the response from the strucDoc committee is likely to be that legal rendering requirement may differ from country to country and maybe even from document to document. Therefore HL7 can't make any generic statements about this other than to provide implementation guidance (best practices). So whether or not adding color is "legally allowable" can only be answered for 1 particular context. Whether color is "CDA R2 spec allowable" .. in my interpretation the answer to that would be yes.
  • IHE (when it uses CDA documents) always makes sure the receiver has the stylesheet (regardless of whether it's used). See the IHE PCC profile.
  • (Bob)Thus, all section.title and section.text values are to be rendered. We don't say anything about order, and I'm aware of applications that do change the order around a bit.
    • (Rene) i.e. sections may be re-ordered by means of a stylesheet. This is not considered to have an impact on human readability.