Win-move is coordination-free (sometimes)

In a recent paper by Hellerstein [15], a tight relationship was conjectured between the number of strata of a Datalog¬ program and the number of “coordination stages” required for its distributed computation. Indeed, Ameloot et al. [9] showed that a query can be computed by a coordinationfree relational transducer network iff it is monotone, thus answering in the affirmative a variant of Hellerstein’s CALM conjecture, based on a particular definition of coordinationfree computation. In this paper, we present three additional models for declarative networking. In these variants, relational transducers have limited access to the way data is distributed. This variation allows transducer networks to compute more queries in a coordination-free manner: e.g., a transducer can check whether a ground atom A over the input schema is in the “scope” of the local node, and then send either A or ¬A to other nodes. We show the surprising result that the query given by the well-founded ...

• Type: Journal
• Year: 2012
• Where: ICDT
• Authors: Daniel Zinn, Todd J. Green, Bertram Ludäscher
• Keywords: Database, Database Management Systems, Free Queries, ICDT 2012, Strict Hierarchy