Over the past few years increasing research effort has been directed towards the automatic verification of infinite-state systems. This paper is concerned with identifying general mathematical structures which can serve as sufficient conditions for achieving decidability. We present decidability results for a class of systems (called well-structured systems) which consist of a finite control part operating on an infinite data domain. The results assume that the data domain is equipped with a preorder which is a well quasi-ordering, such that the transition relation is`m onotonic'' (a simulation) with respect to the preorder. We show that the following properties are decidable for well-structured systems: v Reachability: whether a certain set of control states is reachable. Other safety properties can be reduced to the reachability problem.
In this paper we present the theory of Timed Modal Specifications (TMS) together with its implementation, the tool EPSILON. TMS and EPSILON are timed extensions of respectively Modal Specifications [7, 9] and the TAV system [6, 4]. Also, the theory of TMS is an extension of real-timed process calculi with the specific aim of allowing loose or partial specifications. This allows us to define a notion of refinement, generalizing in a natural way the classical notion of bisimnlation.
Abstract. There have been several attempts to visualize OWL ontologies with UML style diagrams. Unlike ODM approach of defining a UML profile for OWL, we propose an extension to UML class diagrams (hard extension) that allows a more compact OWL visualization. The compactness is achieved through the native power of UML class diagrams extended with optional Manchester encoding for class expressions thus avoiding many explicit anonymous classes typical in ODM. We have implemented the proposed compact visualization in a UML style graphical editor for OWL 2. The editor contains a rich set of graphical layout algorithms for automatic ontology visualization, search facilities, graphical refactoring and interoperability with Protégé 4.
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