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Hybrid Unification in the Description Logic EL

5 pagesPublished: July 29, 2013


Unification in Description Logics (DLs) has been proposed as an inference
service that can, for example, be used to detect redundancies in ontologies.
For the DL EL, which is used to define several large
biomedical ontologies, unification is NP-complete. However, the unification algorithms for EL developed
until recently could not deal with ontologies containing general concept inclusions (GCIs).
In a series of recent papers we have made some progress towards addressing this problem, but the ontologies the
developed unification algorithms can deal with need to satisfy a certain cycle restriction.
In the present paper, we follow a different approach. Instead of restricting the input ontologies,
we generalize the notion of unifiers to so-called hybrid unifiers. Whereas classical unifiers can be viewed as acyclic TBoxes,
hybrid unifiers are cyclic TBoxes, which are interpreted together with the ontology of the input using a hybrid semantics that
combines fixpoint and declarative semantics. We show that hybrid unification in EL is NP-complete

Keyphrases: Description Logic, NP-complete, unification

In: Konstantin Korovin and Barbara Morawska (editors). UNIF 2013. 27th International Workshop on Unification, vol 19, pages 8--12

BibTeX entry
  author    = {Franz Baader and Oliver Fernandez Gil and Barbara Morawska},
  title     = {Hybrid Unification in the Description Logic EL},
  booktitle = {UNIF 2013. 27th International Workshop on Unification},
  editor    = {Konstantin Korovin and Barbara Morawska},
  series    = {EPiC Series in Computing},
  volume    = {19},
  pages     = {8--12},
  year      = {2013},
  publisher = {EasyChair},
  bibsource = {EasyChair,},
  issn      = {2398-7340},
  url       = {},
  doi       = {10.29007/h59c}}
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