This article is part of the supplement: Selected contributions to the First European Conference on SNOMED CT
Proceedings
Formal representation of complex SNOMED CT expressions
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* Corresponding author: Stefan Schulz stschulz@uni-freiburg.de
1 Institute of Medical Biometry and Medical Informatics, University Medical Center, Freiburg, Germany
2 AVERBIS GmbH, Freiburg, Germany
3 Master Program in Health Technology, Pontificial Catholic University of Paraná, Curitiba, Brazil
4 Department of Computer Science, Technical University Dresden, Germany
BMC Medical Informatics and Decision Making 2008, 8(Suppl 1):S9 doi:10.1186/1472-6947-8-S1-S9
Published: 27 October 2008Abstract
Background
Definitory expressions about clinical procedures, findings and diseases constitute a major benefit of a formally founded clinical reference terminology which is ontologically sound and suited for formal reasoning. SNOMED CT claims to support formal reasoning by description-logic based concept definitions.
Methods
On the basis of formal ontology criteria we analyze complex SNOMED CT concepts, such
as "Concussion of Brain with(out) Loss of Consciousness", using alternatively full
first order logics and the description logic 
.
Results
Typical complex SNOMED CT concepts, including negations or not, can be expressed in
full first-order logics. Negations cannot be properly expressed in the description
logic underlying SNOMED CT. All concepts concepts the meaning of which implies a temporal
scope may be subject to diverging interpretations, which are often unclear in SNOMED
CT as their contextual determinants are not made explicit.
Conclusion
The description of complex medical occurrents is ambiguous, as the same situations can be described as (i) a complex occurrent C that has A and B as temporal parts, (ii) a simple occurrent A' defined as a kind of A followed by some B, or (iii) a simple occurrent B' defined as a kind of B preceded by some A. As negative statements in SNOMED CT cannot be exactly represented without a (computationally costly) extension of the set of logical constructors, a solution can be the reification of negative statments (e.g., "Period with no Loss of Consciousness"), or the use of the SNOMED CT context model. However, the interpretation of SNOMED CT context model concepts as description logics axioms is not recommended, because this may entail unintended models.