As the CDISC XML Technologies team finalizes Define-XML v2.1 for internal review an old debate has re-surfaced: how much should the Define-XML specification focus on the regulatory submissions use case versus providing a more general specification that works for a broader set of use cases. As a standard that provides metadata to describe tabular datasets, Define-XML can be used to describe legacy datasets as well as datasets included for submissions. Define-XML has also been used as a specification for datasets. However, Define-XML became the most widely implemented ODM-XML based standard due its role as a required element of regulatory submissions. The importance of ensuring that Define-XML files included in a submission are complete and accurate makes a compelling case for adding rules that specifically target this use case at the risk of reducing its usefulness in other contexts.
Having recently participated in the September HL7 FHIR connectathon in Baltimore, MD it strikes me that the notion of profiling, as it is described for FHIR resources, would provide a good solution for Define-XML. Profiling is where the base resources are adapted for specific use cases. The FHIR specification describes a growing set of base resources that can be used in many different healthcare contexts making FHIR a “platform specification.” It is expected that the platform specification will require adaptations in the form of profiles to meet the needs of specific use cases. Profiles can be used to both constrain and extend resources. They describe the rules that specify which data fields are required vs. optional and which coding systems are used in the stated context. Validators ensure that a specific resource instance conforms to the profile.
Creating Define-XML as a “platform specification” useful across a broad range of use cases, while also creating a regulatory submission profile and implementation guide would seemingly be an ideal solution. As a platform specification Define-XML can be effectively used across a range of use cases. The definition of a regulatory submissions profile would permit the implementation of a comprehensive set of rules effectively adapting Define-XML for use in submissions without concern that these rules are limiting the usefulness of the base standard.
HL7 FHIR profiling: http://www.hl7.org/fhir/profiling.html
Blog post from David Hay: https://fhirblog.com/2015/07/26/creating-and-using-fhir-profiles/