LMNtal: The unifying programming language based on hierarchical graph rewriting

LMNtal is a simple language model based on hierarchical graph rewriting that uses logical variables to represent connectivity and membranes to represent hierarchy. The major goals of LMNtal have been to unify various computational models addressing multiset rewriting, concurrency and mobility, and at the same time to provide a practical programming language based on hierarchical graph rewriting and demonstrate its versatility. The purpose of this paper is to present the aspects of LMNtal as a full-fledged programming language and demonstrate its expressive power using a number of examples. We have designed important language features such as arithmetics, rule application control, modularity and foreign-language interface and integrated them into the hierarchical graph rewriting model. To demonstrate the expressive power of the language, we have successfully encoded diverse related computational models including the λ-calculous, the π-calculus, the ambient calculus and CHR and run them on our LMNtal system.