Semantics Club 09 02 2001
Higraphs, which are structures extending graphs by permitting a hierarchy of nodes, underlie a number of diagrammatic formalisms popular in computing. I will talk about an algebraic account of higraphs (and of a mild extension), with the main focus being on the mathematical structures underlying common operations, such as those required for understanding the semantics of higraphs and Statecharts, and for implementing sound software tools which support them.