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—Let G ¼ ðV ; E; wÞ be a simple digraph, in which all edge weights are nonnegative real numbers. Let G 0 be obtained from G by an application of a set of edge weight updates to G. Let s 2 V and let T s and T 0 s be Shortest Path Trees (SPTs) rooted at s in G and G 0 , respectively. The Dynamic Shortest Path (DSP) problem is to compute T 0 s from T s.… (More)

We investigate the problem of how to evaluate efficiently a collection of shortest path queries on massive graphs that are too big to fit in the main memory. To evaluate a shortest path query efficiently, we introduce two pruning algorithms. These algorithms differ on the extent of materialization of shortest path cost and on how the search space is pruned.… (More)

We investigate the fundamental problem of when a ground atom in a disjunctive database is assumed false. There are basically two diierent approaches for inferring negative information for disjunctive databases; they are Minker's Generalized Closed World Assumption (GCWA) and Ross and Topor's Disjunctive Database Rule (DDR). A problem with the GCWA is that… (More)

With the availability of high-level declarative query languages in an object-oriented database system (OODB), the burden of choosing an efficient execution plan for a query is transferred from the user to the database system. A natural first step is to use the typing constraints imposed by the schema to transform a query into an equivalent one that… (More)

This paper describes a disk-based algorithm for finding shortest paths in a large network system. It employs a strategy of processing the network piece by piece and is based on new algorithms for graph partitioning and for finding shortest paths that overcome the problem of existing approaches. To show that it is scalable to large network systems and is… (More)

We propose and investigate the notion of separability to capture the design goal of independently updatable decompositions. As evidence in favor of separability as a natural concept of independence, we show that it is equivalent to a specialization of the abstract independent mappings defined by Bancilhon and SpyraLos. We then enaracterize separable schemes… (More)

In a context considering in a unique framework all the relations in a database, by means of the notion of global consistency, independent database schemes allow enforcement of constraints to be performed JocaJJy, thus providing independent updatability of the various relations. Independent schemes have hitherto been studied in the presence of functionirl… (More)