CTS2-LE Interoperability

This section describes the set of standards that provide solution developers with standard interfaces for extending the functionality of CTS2-LE and for utilizing CTS2-LE terminology services within their own solutions:

• Common Terminology Services (CTS2): CTS2-LE functional model
• Resource Description Framework (RDF): CTS2-LE internal terminology data format
• SPARQL Protocol And RDF Query Language (SPARQL): CTS2-LE terminology query language
• Fast Healthcare Interoperability Resources (FHIR): CTS2-LE external terminology exchange format

CTS2

The Common Terminology Services Version 2 is a joint standardization effort from HL7 and OMG. The objective was to provide a model and specification for discovering, accessing, distributing and updating terminological resources. While HL7 defined the functional model for managing terminology artifacts, OMG mapped this abstract model onto a concrete information model and service interfaces, which again can be bound to various standards (e.g. SOAP, REST, RDF). Even though CTS2 was developed with healthcare use cases in mind, it can as well be used for managing and distributing terminology resources from other domains.

For further information on CTS2 see:

• OMG CTS2 Homepage (contains links to all published versions of the CTS2 standard)
• Introduction to CTS2 (Presentation from Harold Solbrig, Mayo Clinic)

Use of CTS2 in CTS2-LE

CTS2-LE's internal data model is an RDF-Binding to version 1.0 of the CTS2 standard. By this CTS2-LE supports all terminology resources defined in the CTS2 standard and follows the CTS2 service functional model for discovering and sharing these resources. The full RDF mapping onto the CTS2 model can be found here.

Interoperability with 3rd-Party Solutions

CTS2-LE can manage any semantic resource that complies to the CTS2 functional model. This not only includes terminologies but even networked ontologies and structured knowledge bases. Owners of such semantic resources can easily load these into CTS2-LE and by this utilize the standard SPARQL and REST interfaces of CTS2-LE to provide users access to these resources.

RDF

Modern semantic (web) technologies have its root in mature knowledge representation (KR) methods and techniques. They can be seen as a “Webification” of KR languages such as the Frame Language and Description Logics (DL). In fact, the Resource Description Language (RDF) standard can be considered as a simple frame language as well as a language for semantic nets and OWL has its direct foundation in a certain DL dialect. The semantics of these languages are the theoretical backbone of controlled vocabularies and are widely used to define concrete vocabularies. For instance, SNOMED-CT has the expressivity of the OWL EL++ dialect and even LOINC can be proper represented and processed by means of DL.

Another important aspect is the utilization of RDF for storing and querying linked (big) data. So far many RDF stores (Jena TDB, Virtuoso, etc.) are available and able to hold data in the range of several hundred million triples. Compared to object stores and assuming an average number of 10 object attributes, one can easily store and retrieve several million objects. These capabilities gives CTS2-LE the opportunity to “weave” instance nets for arbitrary medical data objects together with referenced vocabularies.

Use of RDF in CTS2-LE

CTS2-LE manages all semantic resources as RDF graphs. RDF-Schemas are used for implementing the CTS2 functional model on top of RDF. CTS2-LE uses the Jena TDB quad store for efficently managing these graphs.

Interoperability with 3rd-Party Solutions

Using RDF Schema language, further information schemes can be defined and integrated with CTS2-LE. In such scenarios CTS2-LE acts as an integrator that allows to link new artifacs with existing terminologies.

By default the CTS2-LE distribution uses Jena TDB for storing terminology data. This component can easily be exchanged by any other triple store solution (e.g. Virtuoso).

SPARQL

The SPARQL Protocol And RDF Query Language (SPARQL) is a W3C semantic web standard for manipulating and querying RDF graphs. For further information about SPARQL, see:

• W3C SPARQL Working Group homepage with references to all parts of the SPARQL standard
• SPQRQL by Example tutorial containing many example queries to open RDF stores (e.g. medication databases)

Use of SPARQL in CTS2-LE

Due to the full RDF-encoding of all terminology artifacts, CTS2-LE allows for arbitrary queries within and across terminologies, value sets, concepts, and concept relationships. For this means are provided to transmit a standard SPARQL query to CTS2-LE. The query result is provided in standard SPARQL Query Results XML Format.

Interoperability with 3rd-Party Solutions

Third-Party-Solutions have full access to the complete CTS2-LE terminology base through the CTS2-LE SPARQL REST API. Queries must comply to the CTS2-LE CTS2 RDF-Binding.

HL7 FHIR

HL7 Fast Healthcare Interoperability Resources is an HL7 draft standard for exchanging healthcare information in a structured, interoperable and easily implementable manner. In contrast to the constraint-based approach of HL7v3 (e.g. an implementation guide for a referral letter constraints the CDA RMIM, which constraints the HL7 RIM ist), HL7 FHIR is based on modular resources which can be composed to use-case-specific data interchange definitions. FHIR already comes with a catalogue of standard resource definitions which can be composed and tailored to match the need of a specific healthcare data exchange problem. For further information about HL7 FHIR see:

• HL7 FHIR homepage with links to the full FHIR documentation and the FHIR catalogue of standard resource definitions
• Introduction to FHIR (German)
• German FHIR Blog (Simone Heckmann)