Negative Property Assertion Pattern (NPAs)

The basic building blocks of Description Logics (DLs) in general are concept and role constructors (e. g. , intersection, union, nominals, negation etc.), terminological as well as individual axioms. Combining axioms, meaningful statements can be expressed. Additional axiom constructors (so-called syntactical sugar) has been introduced in most ontology language (such as OWL and OWL 2 [1]) in order to simplify ontology modeling, understanding and maintenance. These syntactical sugar axioms can be reduced to basic axioms. A simple example is disjointness of concepts that can be reduced to GCI axioms. However, even experts have often difficulties to understand the reduced forms in comparison to syntactical sugar forms. From the modeling perspective, patterns can support the user in modeling logical meaning that is not directly supported in an ontology language. For instance, OWL 2 provides a syntactical form for modeling negative property assertions whereas using the predecessor OWL 1 one have to model it by a more or less complicated inclusion axiom (or, alternatively, disjoint axiom). The motivation of this pattern is to model negative property assertions (NPAs) in ontology languages such as OWL 1 that do not provide a special construct for it. It is worth mentioning that not all knowledge base systems can be migrated to OWL 2 for several reasons. On the other hand, NPAs modeled according to this pattern can be migrated to OWL 2 using the newly introduced constructor. A negative property assertion as defined in the upcoming OWL 2 states that a given individual i is never connected to a given individual j by a given property expression P . In other words, asserting that i is connected to j by P results in an inconsistent ontology. In this sense this assertion can be considered as a constraint that should not be violated. In contrast, considering an ontology where it cannot be inferred that i is connected to j by p does not necessarily mean that there cannot be such a connection – in fact, it is merely not modeled.