Theona.Stefanis@G.CS.CMU.EDU.UUCP (03/03/87)
PS SEMINAR
MONDAY, 9 March
WeH 5409
3:30
On Visual Formalisms
David Harel
Weizmann Inst., Rehovot, Israel
(At CMU for the year)
A general mathematical object of diagrammatic nature, the higraph, is
presented. Higraphs borrow and extend ideas from Venn-diagrams, graphs and
hypergraphs. They constitute a visual formalism for describing various
kinds of complex entities, particularly those that involve many sets of
objects having intricate structural (i.e., set-theoretic) interrelationships
as well as additional relations af dynamic, causal or other nature.
Higraphs appear to have many applications, as well as a rich theory that
awaits further research. We shall exhibit a number of applications in
database theory (entity-relationship diagrams), artificial intelligence
(semantic and associative nets) and concurrent reactive systems (statecharts).
Statecharts constitute a natural extension of conventional state-transition
diagrams in ways that make them appropriate for describing large real-world
systems, and they will be described in the talk in some detail.
__________________________________________