Using Locality for Efficient Query Evaluation in Various Computation Models (Invited Talk)

In the database theory and logic literature, different notions of locality of queries have been studied, the most prominent being Hanf locality [6, 4, 12] and Gaifman locality [5, 8]. These notions are designed so that, in order to evaluate a local query in a given database, it suffices to look only at small neighbourhoods around tuples of elements that belong to the database. In this talk I want to give a survey of how to use locality for efficient query evaluation in various computation models. In particular, we will take a closer look at how to enumerate query results with constant delay [2, 9, 3], and at how to evaluate queries in a map-reduce like setting [11] or in Pregel [10]. Also, we will have a closer look at how to transform a given local query into a form suitable for exploiting its locality [1, 7]. 1998 ACM Subject Classification H.2.4 [Database Management]: Systems – Query Processing, H.2.3 [Database Management]: Languages – Query Languages, F.4.1 [Mathematical Logic and Formal Languages]: Mathematical Logic – Computational Logic, Model Theory