Showing papers on "Wait-for graph published in 1989"

Finding regular simple paths in graph databases

Abstract: We consider the following problem: given a labelled directed graph G and a regular expression R, find all pairs of nodes connected by a simple path such that the concatenation of the labels along the path satisfies R. The problem is motivated by the observation that many recursive queries can be expressed in this form, and by the implementation of a query language, G+, based on this observation. We show that the problem is in general intractable, but present an algorithm than runs in polynomial time in the size of the graph when the regular expression and the graph are free of conflicts. We also present a class of languages whose expressions can always be evaluated in time polynomial in the size of both the database and the expression, and characterize syntactically the expressions for such languages.

A deadlock detection and recovery algorithm using the formalism of a directed graph matrix

Abstract: A new method of detecting and resolving deadlocked processes in an operating system or database system is presented. It is based on matric theoretic principles and effectively automates tasks heretofore only achievable via adjacency list representations. Two algorithms are presented with examples for each.

Describing distributed systems by categorical graph grammars

Abstract: The structure of an asynchronous system of processes is described by a labeled hypergraph. It represents both the past and the present of the system. The set of all possible traces is defined by a hypergraph grammar. In the graph, actions and process states are represented by hyperedges. Each hyperedge is connected to some event nodes, some of which are considered to be predecessors of the edge, whereas others are successor nodes. This induces a partial ordering of the hyperedges. Some aspects of the Ada rendezvous are used as an example and translated into hypergraph productions.

Modular System Design Applying Graph Grammars Techniques

Abstract: In this paper we combine notions from the well known theory of algebraic graph grammars with the theory of large software system specifications based on modules. The intent is to tackle the problem of designing a modular system (if it exists) which realizes a given goal specification using a library of module specifications and a collection of "primitive" realized data type specifications. The interfaces of the module are treated as productions and direct derivations and operations on productions are converted into system design.

A flow graph analysis algorithm for a data driven reconfigurable parallel pipelined computer architecture

Abstract: A flow graph analysis algorithm (FGAA) and its proof, utilized in conjunction with a data-driven reconfigurable parallel-pipelined computer architecture system, are presented. The architectural system was developed such that any real-time data-driven application describable as a data-flow graph could be executed on the system. A requirement for utilization of the architectural system is an ability to describe the structure and linkages of the data-flow graph to the operating system (OS). This requirement is accomplished by a data-flow language and interpreter, which is described. A second requirement is that the OS must have the capability of algorithmically assigning processes of a flow graph to specific computing elements (CEs) of the architecture, in a manner that assures that real-time timing constraints from input node to output node of any data flow graph can be met. A third requirement is that processes must be assigned to CEs in a manner which minimizes system resources. The FGAA was developed to meet these latter requirements. >