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This paper presents a Query-and-Relax System (QaRS) designed to facilitate the exploitation of large knowledge bases. QaRS proposes a graphical interface to construct a SPARQL query and use different cooperative answering techniques. The proposed cooperative techniques help users in finding alternative answers when their queries fail or do not return the expected number of answers. The present demonstration includes three main relaxation strategies: (1)- automatic where the system automatically relaxes the query based on similarity measures, (2)- manual where the user can specify the conditions that can or cannot be relaxed as well as the tolerance values and (3)- interactive where QaRS computes the causes of the query failure as a set of Minimal Failing Subqueries (MFSs )a nd then the user chooses the relaxation operators according to these MFSs.

This paper introduces a new type of database queries involving preferences. The idea is to consider competitive conditional preference clauses structured as a tree, of the type “preferably P1 or ⋅⋅⋅ or Pn; if P1 then preferably P1,1 or …; if P2 then preferably P2,1 or …,” where the Pis are not exclusive (thus the notion of competition). The paper defines two possible interpretations of such queries and outlines two evaluation techniques which follow from them. © 2010 Wiley Periodicals, Inc.

Uncertain relations between temporal points are represented by means of possibility distributions over the three basic relations precedes, equals, and follows. Operations for computing inverse relation, for composing relations, for combining relations coming from different sources and pertaining to the same temporal points, or for representing negative information are defined. An illustrative example of representation and reasoning with uncertain temporal relations is provided. This article shows how possibilistic temporal uncertainty can be handled in the setting of point algebra. Moreover, the article emphasizes the advantages of the possibilistic approach over a probabilistic approach previously proposed. This work does for the temporal point algebra what the authors previously did for the temporal interval algebra. © 2007 Wiley Periodicals, Inc. Int J Int Syst 22: 157–179, 2007.