Navigating the EL Subsumption Hierarchy

Francesco Kriegel
2021 International Workshop on Description Logics  
The EL subsumption hierarchy consists of all EL concept descriptions and is partially ordered by subsumption. In order to navigate within this hierarchy, one can go up to subsumers and down to subsumees. We analyze how smallest steps can be made. Specifically, we show how all upper neighbors as well as all lower neighbors of a given EL concept description can be efficiently computed, where two concepts are neighbors if one subsumes the other and there is no third concept in between. We further
more » ... how that the hierarchy contains very long chains: there is a sequence of concepts Cn with size linear in n such that each chain of neighbors from ⊤ to Cn has at least n-fold exponential length. As applications, we provide a template for determining upper complexity bounds for deciding whether a concept is maximally general or maximally specific w.r.t. a property, we construct a metric on the set of all EL concept descriptions, we introduce a similarity measure that fulfills the triangle inequality, and we conclude that an uninformed search for a target concept by subsequently computing neighbors or, equivalently, along an ideal refinement operator is not feasible in practical applications.
dblp:conf/dlog/Kriegel21 fatcat:rftswbz2qnb4xa7i2viy6gmi4y