Variable-Strength Conditional Preferences for Ranking Objects in Ontologies

15 Pages Posted: 11 Jul 2018 First Look: Accepted

See all articles by Thomas Lukasiewicz

Thomas Lukasiewicz

University of Oxford - Computing Laboratory

Jorg Schellhase

University of Kassel - Information Systems


We introduce conditional preference bases as a means for ranking objects in ontologies. Conditional preference bases consist of a description logic knowledge base and a finite set of conditional preferences, which are statements of the form "generally, in the context φ, property α is preferred over property -α with strength s". They are inspired by variable-strength defaults in conditional knowledge bases. We define the notion of consistency for conditional preference bases, and we show how consistent conditional preference bases can be used for ranking objects in ontologies, where every object represents essentially a set of individuals that are sharing the same ranking-relevant properties. More concretely, we define two object rankings, denoted κsum and κlex, which evaluate the strengths of conditional preferences in an additive and a lexicographic way, respectively. Furthermore, we provide algorithms for the main computational tasks for ranking objects under conditional preference bases, we analyze the complexity of these tasks, and we delineate a tractable special case. To give evidence of the usefulness of this approach in practice, we describe two applications in the areas of product and literature search, where it allows especially for a flexible user-defined ranking of the query results reflecting personal preferences.

Keywords: Variable-Strength Conditional Preference, Ranking, Ontology, Description Logic, Semantic Web, Literature Search, Algorithms and Complexity

Suggested Citation

Lukasiewicz, Thomas and Schellhase, Jorg, Variable-Strength Conditional Preferences for Ranking Objects in Ontologies (2007). Journal of Web Semantics First Look 5_3_4. Available at SSRN: https://ssrn.com/abstract=3199366 or http://dx.doi.org/10.2139/ssrn.3199366

Thomas Lukasiewicz (Contact Author)

University of Oxford - Computing Laboratory ( email )

Wolfson Building
Parks Road
Oxford, OX1 3QD
United Kingdom

Jorg Schellhase

University of Kassel - Information Systems ( email )

Nora-Platiel 4
Kassel, 34127

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