Higraph

Abstract: This paper presents a graphical modeling method and tool for DEVS model and DEVS-based combined discrete/continuous model specification. In DEVS-based modeling, atomic model behavior specification is organized around different phases which define a partition of the state space of the model. The phase transitions depict the qualitative state changes and naturally lend themselves to be represented by a state transition diagram. Our representation of these phase transitions is based on the higraph extension to conventional graph representations. In higraphs, the area of the diagram is used to represent set enclosure and exclusion and the Cartesian product which leads to remarkable reduction in the diagram's complexity. An interactive modeling tool based on the graphical representation developed is presented.

Abstract: We present an algorithm for the aesthetic drawing of basic hierarchical blob structures, of the kind found in higraphs and statecharts and in other diagrams in which hierarchy is depicted as topological inclusion. Our work could also be useful in window system dynamics, and possibly also in things like newspaper layout, etc. Several criteria for aesthetics are formulated, and we discuss their motivation, our methods of implementation and the algorithm's performance.

Abstract: This paper examines the use of higraphs as a means of representing dependencies and relationships among multiple aspects of system development models (e.g., requirements, hardware, software, testing concerns). We show how some well-known diagram types in UML have counterpart higraph representations, how these models incorporate hierarchy and orthogonality, and how each model can be connected to the others in a useful (and formal) manner. Present-day visual modeling languages such as UML and SysML do not readily support: (1) the traceability mechanisms required for the tracking of requirements changes and (2) built-in support for systems validation. Higraphs also deviate from UML and SysML in their ability to model requirements, rules, and domain knowledge relevant to the development of models for system behavior and system structure. To accommodate these demands, an extension to the basic mathematical definition of higraphs is proposed. Capabilities of the extended higraph model are examined through the model development for an office network computing system. © 2008 Wiley Periodicals, Inc. Syst Eng

Abstract: Higraphs, which are structures extending graphs by permitting a hierarchy of nodes, underlie a number of diagrammatic formalisms popular in computing. We provide an algebraic account of higraphs (and of a mild extension), with our 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.