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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 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)
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)