A Therapeutic Layered Cake

With all the talk about the PCAST Report, I've been doing some Systems thinking on semantic interoperability in healthcare IT. Trying to put all the pieces together, I remembered Tim Berners-Lee's "Semantic Web Layer Cake".




The Semantic Web layer Cake has gone through several iterations over the years (see James Hendler's presentation on that subject). However, I think it can still be very helpful in visualizing a unified framework for addressing the challenges of semantic interoperability in Healthcare IT.

As we move to Stage 2 of Meaningful Use, I believe Clinical Decision Support (CDS) will take center stage. Beyond currently used XML-based data structures (such as HL7 v3 messages), this will put an increased emphasis on medical terminologies, ontologies, and knowledge representation in OWL. For example, ICD-11 is being developed using OWL to allow consistency checking and linking to other biomedical terminologies and ontologies. Equally important to knowledge representation, but not shown in the layer cake above is the Simple Knowledge Organization System (SKOS) specification.

In a report entitled "Semantic Interoperability Deployment and Research Roadmap", Alan Rector summarized the difference between the notions of ontology, knowledge representation, and data model:

• Ontology – A representation of what is universally true, including what is true by definition
  
  
• Knowledge Representation or "Background knowledge resource" – a representation of what is generally true, or widely known to be true in some specific instance. In general, the knowledge representation is formulated in terms of and indexed by the Ontology.
  
  
• Information model or Data model a model of how information is structured in a given software system, message, or electronic health record. In general, the data structures carry codes for the ontology as their content.
  

Clinical guidelines are published in the form of narrative text, sometimes with an evaluation algorithm. The translation of those guidelines into an executable representation is a complex and costly process. Several formalisms and standards have been proposed such as the Arden Syntax, GLIF, GELLO, and GEM. However, none of these standards has been widely adopted. Developed with inputs from the Business Rules, Logic Programming, and Semantic Web communities, the W3C Rule Interchange Format (RIF) can help with the interchange of executable Clinical Decision Support (CDS) rules in addition to adding reasoning capabilities to patient records. This example shows how decision support rules could be exchanged between two rules engines (Drools and Jess) using the RIF PRD syntax, a standard XML serialization format for production rule languages.

Existing patient records marked up in XML HITSP C32 or ASTM CCR can be lifted into RDF statements (with XSLT or XQuery for example) and queried using SPARQL.

Proof, Trust, and Cryptography are being currently addressed by various standards and specifications in the healthcare industry notably the OASIS Cross-Enterprise Security and Privacy Authorization (XSPA) Profiles of XACML, SAML, and WS-Trust.

On the User Interface side, I see HTML5 giving both Flex and Silverlight a run for their money in the next few years. This will be driven in part by the demand for mobile health (mHealth).