This section outlines the rationale for distributing an OWL representation of the  stated view of  concept definitions and provides an overview of the way OWL axioms are represented in  SNOMED CT release files.  More detailed information is published separately in the  SNOMED CT OWL Guide and the  SNOMED CT Logic Profile Specification.

Rationale for Using OWL

The mismatch between the requirements for representing enhanced  concept definitions and the capabilities of the current  stated relationship file might in theory be addressed by addition of columns to the file or adding additional information in reference sets. However, in practice this would create a more complex solution able to support a specific set of enhanced features.

Adopting the well-established OWL standards formats offers a more flexible solution that can represent the full range of  description logic features. This approach enables  SNOMED Internation to specify a particular logic profile to be applied to current releases of  SNOMED CT, with the option to extend that profile in the future. Future revisions of the logic profile would not require a change in the distribution file structure provided these were supported by an OWL syntax.

OWL Axioms

OWL axioms can be represented using several different syntaxes. SNOMED International has chose the OWL Functional Syntax as its standard representation.

The OWL Functional Syntax is a formal representation of the web ontology language (OWL) as a simple text base syntax that is used as a bridge between the structural specification and various concrete syntaxes.

OWL Expression Axiom Set

OWL axioms are distributed in a  reference set that follows the  OWL Expression Reference Set specification. The axiom itself is contained in a string field and the  concept whose definition it contributes to is referenced by the the  referencedComponentId. Although a single row in the reference set can provide a  sufficient definition, the definition of a single concept can also include several axioms each represented by a row in the reference set.

Comparing Stated Relationships and OWL Axioms

Figure Diagrammatic representation of the definition of appendectomy

Figure shows the diagrammatic representation of the  stated view of the definition of  80146002 | Appendectomy|Table shows the same definition as represented by three rows in the  stated relationship file together with the  definitionStatusId in the  concept file.

Table Stated relationships and definition status for the concept appendectomy









Table shows a row in the  OWL axiom reference set file representing the same definition. As shown by this example, a single  sufficient definition is represented by a single row in the reference set. However, some  concept definitions may require multiple rows in the reference set. Situations in which multiple row are required include:

Table Example of OWL axiom refset representation of the definition of appendectomy


effective Time










EquivalentClasses(:80146002 ObjectIntersectionOf(:71388002 ObjectSomeValuesFrom(:609096000 ObjectIntersectionOf(ObjectSomeValuesFrom(:260686004 :129304002) ObjectSomeValuesFrom(:405813007 :66754008)))))

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