A New Tractable Description Logic under Categorical Semantics

TL;DR

This paper introduces a new, tractable extension of the Description Logic EL that incorporates negative knowledge through weakened categorical semantics, enabling more expressive biomedical ontologies without sacrificing computational efficiency.

Contribution

It proposes a novel extension of EL with weakened negation and categorical semantics, maintaining tractability while allowing negative knowledge representation.

Findings

The new logic is more expressive than EL with bottom, transitive roles, and role inclusion.

Categorical semantics are weakened by removing properties responsible for intractability.

The approach preserves tractability while enhancing expressiveness for biomedical ontologies.

Abstract

Biomedical ontologies contain numerous concept or role names involving negative knowledge such as lacks_part, absence_of. Such a representation with labels rather than logical constructors would not allow a reasoner to interpret lacks_part as a kind of negation of has_part. It is known that adding negation to the tractable Description Logic (DL) EL allowing for conjunction, existential restriction and concept inclusion makes it intractable since the obtained logic includes implicitly disjunction and universal restriction which interact with other constructors. In this paper, we propose a new extension of EL with a weakened negation allowing to represent negative knowledge while retaining tractability. To this end, we introduce categorical semantics of all logical constructors of the DL SH including EL with disjunction, negation, universal restriction, role inclusion and transitive roles. The categorical semantics of a logical constructor is usually described as a set of categorical properties referring to several objects without using set membership. To restore tractability, we have to weaken semantics of disjunction and universal restriction by identifying \emph{independent} categorical properties that are responsible for intractability, and dropping them from the set of categorical properties. We show that the logic resulting from weakening semantics is more expressive than EL with the bottom concept, transitive roles and role inclusion.