Porgy Strategy Language: User Manual

This document provides concrete syntax illustrated with ex- amples for the Porgy’s strategy language and the language for rule algorithm and conditions. Porgy is a visual, interactive modelling tool based on port graph rewriting. In Porgy, system states are represented by port graphs, and the dynamic evolution of the system is defined via port graph rewrite rules. Strategy expressions are used to control the application of rules, more precisely, strategy expressions indicate both the rule to be applied at each step in a rewriting derivation, and the position in the graph where the rule is applied (the latter is done via focusing constructs). Some of the strategy constructs are strongly inspired from term rewriting languages such as Elan [Borovansk´yBorovansk´y et al., 1998], Stratego [Visser, 2001] and Tom [Balland et al., 2007]. Focusing operators are not present in term rewriting languages (although they rely on implicit traversal strategies). The direct management of positions in strategy expressions, via the distinguished position and banned subgraphs in the target graph and in a located port graph rewrite rule are original features of the language and are managed using positioning constructs. This document describes the concrete syntax of strategy expressions, explains how the different kinds of constructs are used, and provides examples.