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This paper presents DEDALE, a spatial database syst,cm irltended to overcome some limitations of current systems by providing an abstract and non-specialized data model and query language for the representation and manipulation of spatial objects. DEDALE relies on a logical model based on linear constraints, which generalizes the constraint database model of [KKRSO]. While in the classical constraint model, spatial data is always decomposed into its convex components, in DEDALE holes are allowed to fit the need of pract,ical applications.The logical representation of spatial dat,il although slightly more costly in memory, has the advantage of simplifying the algorithms. DEUALE relics on nest,c,tl rrlations, in which all sorts of data (thematic, spst,ial, etc.) arc stored in a uniform fashion. This new d&a model supports declarative query languages, which allow an intuitive and efficient manipulation of spatial objects. Their forma1 foundation constitutes a basis for practical query optimization. We describe several evaluation rules tailored for geometric data and give the specification of an optimizer module for spatial queries. Except for the latter module, the system has been fully implemented upon the 02 DBMS, thus proving the effectiveness of a constraint-based approach for the design of spatial database systems

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Abstract. We propose a rule-based language, Netlog, to express distributed applications such as communication protocols or P2P applications in a declarative manner. The language extends Datalog with communication primitives, as well as aggregation and non-deterministic constructs, standard in network applications. Our contribution is twofold. First we define a sound distributed fixpoint semantics, which takes explicitly into account the in-node behavior as well as the communication between nodes, and solves semantic problems raised in declarative networking. Second, we show that syntactic restrictions over the programs can ensure polynomial bounds on the complexity (time and message) of the distributed execution. The language has been implemented and runs over a virtual machine, Netquest, which relies on a DBMS. Netlog programs are partly compiled into SQL queries, which makes them portable over heterogeneous architecture.