Abstraction in Reasoning about Higraph-Based Systems

ion in Reasoning about Higraph-Based Systems John Power and Konstantinos Tourlas Division of Informatics, The University of Edinburgh, King’s Buildings, EH9 3JZ, United Kingdom {ajp,kxt}@inf.ed.ac.uk Abstract. Higraphs, a kind of hierarchical graph, underlie a number of sophisticated diagrammatic formalisms, including Statecharts. Naturally arising from hierarchy in higraphs is an abstraction operation known as zooming out, which is of profound importance to reasoning about higraph-based systems. We motivate how, in general, the use of zooming in reasoning requires sophisticated extensions to the basic notion of higraph and a careful definition of higraph dynamics (i.e. semantics), which we contribute. Our main results characterise zooming by means of a universal property and establish a precise relationship between the dynamics of a higraph and that of its zoom-out. Higraphs, a kind of hierarchical graph, underlie a number of sophisticated diagrammatic formalisms, including Statecharts. Naturally arising from hierarchy in higraphs is an abstraction operation known as zooming out, which is of profound importance to reasoning about higraph-based systems. We motivate how, in general, the use of zooming in reasoning requires sophisticated extensions to the basic notion of higraph and a careful definition of higraph dynamics (i.e. semantics), which we contribute. Our main results characterise zooming by means of a universal property and establish a precise relationship between the dynamics of a higraph and that of its zoom-out.