Nondeterministic control structures for graph rewriting systems

Abstract

The work reported here is part of the IPSEN3 project whose very goal is the development of an Integrated Project Support ENvironment. Within this project directed, attributed, node- and edge- labeled graphs (diane graphs) are used to model the internal structure of software documents and PROgrammed Graph REwriting SyStems are used to specify the operational behavior of document processing tools like syntax-directed editors, static analyzers, or incremental compilers and interpreters. Recently a very high-level language, named PROGRESS, has been developed to support these activities. This language offers its users a convenient, partly textual, partly graphical concrete syntax and a rich system of consistency checking rules (mainly type compatibility rules) for the underlying calculus of programmed diane-graph rewriting systems. This paper presents a partly imperative, partly rule-oriented sublanguage of PROGRESS for composing complex graph queries and graph transformations (transactions) out of simple subgraph tests and graph rewriting rules (productions). It also contains a formal definition of this sublanguage by mapping its main control structures onto so-called nondeterministic control flow graphs. We believe that these control structures or at least the underlying flow graph formalism could be incorporated into many graph-/tree-/term- rewriting systems in order to control the nondeterministic selection and application of rewriting rules.