HyperLMNtal: An Extension of a Hierarchical Graph Rewriting Model

LMNtal (pronounced “elemental”) is a language model based on hierarchical graph rewriting that uses point-to-point links to represent connectivity and membranes to represent hierarchy. LMNtal was designed to be a substrate language of various computational models, especially those addressing concurrency, mobility and multiset rewriting. Although point-to-point links and membranes could be used together to represent multipoint connectivity, our experiences with LMNtal showed that hyperlinks would be an important and useful extension to the language. We have accordingly expanded LMNtal into a hierarchical hypergraph rewriting language model, HyperLMNtal. HyperLMNtal enabled concise description of computational models involving flexible and diverse forms of references between data; in particular, it enabled efficient encoding of a constraint processing language CHR in terms of both performance and computational complexity. This paper describes the design and implementation of HyperLMNtal as a case study of language evolution.