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Document Information

Author: Craig Stancl, Scott Bauer, Cory Endle
Team: LexEVS
Contract: 16X237
National Institutes of Heath
US Department of Health and Human Services

Contents of this Page

The purpose of this document is to document the project summary report for the National Cancer Institute Center for Biomedical Informatics and Information Technology (NCI CBIIT) for the duration of this contract (October 1, 2017 - September 30th, 2018).


LexEVS is the central EVS terminology server developed by the National Cancer Institute (NCI).  LexEVS provides a common terminology model and open access to a wide range of terminologies, terminology value sets, and cross-terminology mappings needed by NCI and its partners. LexEVS provides a collection of program interfaces, affording users and developers open access to both controlled terminologies available from the NCI EVS and other supported terminologies. 
The components that make up the LexEVS Terminology Service are:
  • LexEVS API - A Java interface based on the LexGrid Object Model to access LexEVS content
  • LexEVS REST - Common Terminology Services 2 (CTS2) based REST service to access LexEVS content
  • LexEVS Distributed API - A Java interface to provide remote client access to the native LexEVS API to access LexEVS content
  • URI Resolver Server - A REST service for translating identifiers into valid URIs
  • Developer Tools - Tooling (graphical user interfaces) to support server administration, query testing, and value set development for developers

Features 2017-18

  • Efficient Value Set Resolution using Source Asserted Value Sets
    • The source of value sets is the NCI Thesaurus (NCIt), and since the NCIt contains logical, computable assertions about what value sets are in its system, business logic has moved towards direct access to the code system rather than external defining files.  This has been a collaborative effort with NCIt curators and has resulted in improved loading efficiency of value set definitions and resolved value set coding schemes.
  • Detection of Value Set Updates
    • An additional API that detects value set updates has also been made available.  This represents an additional efficiency for value set loading.  
  • Representation of Value Set Hierarchy
    • Other assertions made in the NCIt about the hierarchical style storage of value sets also now have an API as well.  This is specific to the NCIt source at this time.  
  • Fully Dynamic Source Asserted Value Set Resolution
    • Source asserted value set API can fully resolve directly against the source coding scheme.
  • Source Asserted Value Set Search
    • New search API implemented against Value Sets
  • LexEVS Services Support for Source Asserted Value Sets
    • LexEVS Distributed API and LexEVS REST services updated to fully support Source Asserted Value Sets 
  • Enhanced Loaders
    • Continued enhancement of existing LexEVS Loaders
      • Notably, expanded OWL2 and RRF support for MED-RT

Future Task

  • Enhanced OWL2 support
    • To support OWL2 class expressions, model changes will be required.  
  • Enhanced LexEVS REST Support
    • Expand LexEVS REST services by implementing additional features
  • Provide additional services to support LexEVS service.
    • Implement microservices to support additional features  
  • REST Text Search Service for Metathesaurus
    • Implement a prototype to demonstrate text search
  • Migration from LexEVS Distributed API to LexEVS REST services 




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