Showing papers by "Alessandro D'Atri published in 1985"
TL;DR: In this article, the concept of strong equivalence between directed hypergraphs, based on the notion of kernel, is considered and its properties are analyzed and the computational complexity of testing strong equivalences and determining a minimal strongly equivalent hypergraph is examined and algorithms which solve such problems in polynomial time are provided.
Abstract: Various concepts of equivalence among graphs and among hypergraphs have been studied by several authors. In this paper the concept of strong equivalence between directed hypergraphs, based on the notion of kernel, is considered and its properties are analyzed. The computational complexity of testing strong equivalence and of determining a minimal strongly equivalent hypergraph is examined and algorithms which solve such problems in polynomial time are provided.
9 citations
TL;DR: It is shown that the problem of deciding whether there exists a Berge-, γ-, or α-acyclic view in a general database scheme is NP-complete and that the Problem of decidingWhether there exists an Berge- or γ-acyClic view on an α-ACYclic scheme is also computationally intractable.
6 citations