This section gives you an overview with examples of the additional description logic features that Snow Owl supports on top of SNOMED CT's default expressibility. Snow Owl supports a variety of different reasoners that should be used to semantically evaluate the changes made using advanced level ontology authoring.

Depending on the meaning that you would like to express, on top of SNOMED CT's current ontological expressibility, you can use universal restriction, disjoint concepts, negation, disjunction and at special use cases numerical datatypes as well. When classifying, you should make sure that you select the appropriate classifier for the semantic evaluation.

Running the classification

To start the classification, press the Classify SNOMED CT ontology button in the main toolbar. The reasoner now evaluates the defining relationships between the concepts to infer new connections and identify unnecessary or redundant ones. Afterwards an ontology-comparison process calculates the changes that the reasoner found between the old and the new ontology. When the process is completed, a dialog pops up that gives you a detailed overview of the new relationships. If the changes are accepted newly inferred relationships will be added, and redundant relationships set to inactive with an updated effective time.

Classification Results

Equivalency checking on save

The concept editor lets you check to see if a new concept is equivalent to an existing concept's definition. This equivalency check is performed using the description logic reasoner set in File > Preferences > Snow Owl > Reasoners.

Equivalency checking action

Quick fix for equivalency errors

We offer a "quick fix" for equivalent concepts. Following classification, equivalency errors are displayed in the problems view. You can now select one or more concepts to quick fix, which simply changes the defined status on the offending concept to primitive.

Quick-fixing an equivalency error

This is useful to bypass known errors following programmatic generation of large ontologies.