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Controlled vocabularies (also known as code systems or terminologies) are common information artefacts in healthcare. They allow for univocally and precisely referencing of concepts and are core foundation of any semantic processing of health data. In particular all electronic communication in healthcare relies on coded concepts for semantic interoperability and automated data processing.

The Object Management Group's Common Terminology Services Version 2 (CTS2) standard defines an accepted industry standard service interface to share, query and maintain value sets and other terminology artifacts. The CTS2 specification is structured within a platform independent model that provides two profiles:

1. Structural profiles define how code systems, associations, or value sets are organized;
2. Functional profiles define fundamental operations of persistent storage (CRUD) in an information system that change these structures.

One method to achieve compliance with the structural profiles of CTS2 is to use semantic web technologies that are widely used for vocabularies. In this way, CTS2 artifacts such as code systems, code system elements (i.e., codes and their designations), associations and value sets (i.e., sets of code system elements) can be processed with reasoning engines including code member validations.

The CTS2 Linked Data Edition (CTS2-LE) terminology server provided by Fraunhofer FOKUS follows that foundation. It relies on the the Resource Description Framework (RDF) in conjunction with a RDFS-based schema vocabulary oriented towards the Frame Logic. So-called RDF signatures, based on this schema vocabulary, describe structural constraints according to the CTS2 information model. Likewise, arbitrary object graphs can be processed and stored with these RDF signatures.

CTS2-LE Overview

This section provides an overview about CTS2-LE. It introduces the CTS2-LE building blocks and summarizes the most important functional features provided by CTS2-LE.

CTS2-LE Fact Sheet (German)

The CTS2-LE Fact Sheet provides an overview of CTS2-LE considering the implemented CTS2 functionalities and additional usability related features.

CTS2-LE Building Blocks

The foundation of CTS2-LE features a structural compliance to the OMG CTS2 Information Model, is linked-data ready by the means of W3C RDF, and is accessible through a HL7 FHIR and REST API as well as supporting the definition, composition and import of value sets. The knowledge base functionality is implemented with RDF as the representation language providing linkage capabilities for intra- or cross-domain artifacts such as HL7 CDA and HL7 FHIR. This section describes the architecture and internal design of CTS2-LE.

CTS2-LE Supported Terminologies

CTS2-LE is highly suitable for representing netlike vocabularies of varying complexity. Thus, it facilitates the integration of several healthcare relevant terminologies. This section gives an overview of the vocabularies that can be loaded so far.

CTS2-LE Interoperability

CTS2-LE is build upon international standards and provides multiple standard interfaces for connecting to external services. This section gives an overview on the standards supported by CTS2-LE and how these can be utilized for integrating CTS2-LE with third party products.

Further Information Sources for CTS2-LE

Fraunhofer FOKUS has published various papers and brochures about CTS2-LE in particular and terminology services in general. This section provides links to online resources related to CTS2 and CTS2-LE.

Licence and Availability Notes

When distributing CTS2-LE along with its supported terminologies, licence restrictions have to be considered. This section outlines the terminology specific terms of distribution.

CTS2-LE Installation, Deployment, and Setup

This section covers the installation and initial setup of CTS-LE within an organization.

Prerequisites

This section describes the hardware, OS and network requirements for installing CTS2-LE as a stand-alone-system on a server.

Installation, Deployment, and Setup V3

V3 is designed to run in distributed mode, i.e. search engine (solr), database (fuseki quad store), and service layer can run separately. Furthermore, terminologies can be loaded remotely.

Security Configuration

CTS2-LE standard configuration allows unrestricted read access while administrative functionalities (e. g. loading/updating terminologies) is restricted to registered named users. This section describes how to configure these defaut security settings and how enhanced security services (e. g. full access control) may be linked with CTS2-LE.

CTS2-LE Web Services

CTS2-LE provides a simple REST interface for integrating CTS2-LE terminology services with custom and third-party applications. This section provides the technical specification of the CTS2-LE REST Application Programming Interface including sample code snippets for each interface.

General

• Suggester update

The suggester has to be updated whenever a code system is loaded. The suggester is used for searches within the navigation frontend.

• Search index update

Update only has to be invoked for RDF triple loading or if elements of a resource are modified via editing. The search index is automatically updated whenever a code system is loaded.

• Delete resource by uri and version

FHIR R4

CTS2-LE supports essential parts of the FHIR REST API for

• code systems
• value sets and
• concept maps

that will deprecate most of the API below. Not all parameters are supported, but in the context of customization for a project it will be enhanced. The following operations are supported:

Resource-type-independent

• read (currently, only for code systems and value sets)
• update (Special Parameters)

if extra parameter ext:deactivateExistent == true then the existing resource is not deleted, only deactivated. It is recommended for huge stores/indexes due to high costs of updates in quad stores.

• delete by resource id (unconditional)

Code Systems

• lookup

supported parameters: code, system, version, coding, displayLanguage

• validate-code

supported parameters: url, code, version, display, coding, codeableConcept, displayLanguage

• subsumes

supported parameters: codeA, codeB, system, version, codingA, codingB

Value Sets

• expand

supported parameters: url, valueSetVersion, includeDesignations

• validate-code

supported parameters: url, valueSetVersion, code, system, systemVersion, display, coding, codeableConcept, displayLanguage

Concept Maps

• translate

supported parameters: url, code, system, version, coding, codeableConcept, targetsystem

OWL

• update

For index updating and deletion see General

FHIR-oriented (deprecated, use FHIR R4 instead)

Read Code System

reads a code system.

Resolve Value Set (multi-modal)

provides means to resolve and/or fetch an FHIR origined value set (or code system).

Resolve Complete Value Set

provides means to resolve and/or fetch an FHIR origined value set (or code system) which is identified by it's URI.

Request Concept Details

used for fetching the details of a concept which is identified through a codesystem and code.

Check Value Set Containment

allows to check wether a code (from a code system) is contained in a Value Set.

Update Value Set / Code System

allows to create or update a FHIR coded value set (or code system).

Delete Value Set / Code System

allows to delete a FHIR coded value set (or code system).

SPARQL

SPARQL Query

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. This API provides means to transmit a standard SPARQL query to CTS2-LE. The query result is provided in standard SPARQL Query Results XML Format.

CTS2 REST-API (deprecated in future)

Most of the API below is supported by the FHIR R4 API. FHIR is emerging as a modern standard to cover all aspects of interoperable communication between all agents (human or machine) in eHealth.

The below services mainly implement the standard services as specified in the documents provided by OMG/HL7. For further references (to the normative documents or XML schema files) please visit this site. Please note that these services are not fully tested at this time. Hence, they are not available on any machine.

Read Code Systems and Code System Versions

Read Entity Descriptions

Read Maps and Map Versions

Read Value Set Definitions

Sharing Value Sets (SVS)

Update Codesystem or Value Set

Retrieve Codesystem or Value Set

Classification Markup Language (ClaML)

Update Codesystem

Retrieve Codesystem

Futher Services

Concept Suggestion

retrieve results from suggestion (plain, restricted)

Concept Search

perform search operations (plain, restricted, similar)

EXCEL/CSV Value Set Catalog Import

CTS2-LE Solution Management

CTS2-LE Licensing

CTS2-LE is distributed by Fraunhofer FOKUS under a commercial license. This section provides information about the licensing terms and conditions for various CTS2-LE usage scenarios.

CTS2-LE Release Management

Fraunhofer FOKUS is continuosly maintaining and further developing CTS2-LE. This section gives insight into the CTS2-LE development roadmap by sketching CTS2-LE add-ons and improvements which are under development at Fraunhofer FOKUS.

CTS2-LE Wish List

You have an idea for a cool new feature for CTS2-LE? There is some interface you desperately need for your terminology consuming solution? You have discovered a useful terminology that should be distributed through the public CTS2-LE? The CTS2-LE Wish List summarizes all ideas for new CTS2-LE featurs and acts as a major input to the CTS2-LE development roadmap.