Conditional Preferences: A New Semantics for Database Queries

Preference queries aim to retrieve from large databases those objects that better match user’s requirements. Approaches proposed so far in the DB field for specifying preferences are limited when one needs to consider conditional, rather than absolute, preferences (e.g., I prefer driving by car in winter, and by motorbike in summer), which are common in context-aware applications. CP-nets are a powerful formalism for concisely representing such preferences, which has its roots in decision making problems. However, CP-nets, being based on a ceteris paribus (all else being equal) interpretation, are hardly applicable in complex DB scenarios. In this paper we introduce a new totalitarian (i.e., not ceteris paribus) semantics for CP-nets. We prove that our semantics is equivalent to ceteris paribus for complete acyclic CP-nets, whereas it avoids some counterintuitive effects of ceteris paribus when the CP-net is partially specified.