Petri nets are known as a modeling language for concurrent and distributed systems. In recent years, various object-oriented Petri nets were proposed, and we are proposing a kind of object-oriented Petri nets, called multi agent nets (MANs). In this letter, we consider the reachability analysis of MANs. We propose an algorithm for generating an abstract state space of a multi agent net, and report results of computational experiments.

This paper describes glyph representation, that is, shape representation of inheritance relationships between a superclass and subclasses in an object-oriented programming language. The inheritance relationships in object-oriented programming languages are usually represented in a visual programming environment by a diagram of a tree graph or a nested structure. That diagram is not integrated with a code view showing control and data flows. Using the proposed representation, one can understand the inheritance relationships of classes and the assignment compatibility or type conformance just by seeing the glyphs. One thus does not need to look at a hierarchy diagram in order to recognize them. The inheritance relationships are represented by inclusion relationships of glyphs. Methods for generating suitable glyphs from a class hierarchy are also described, as is a prototype system for glyph generation. Experiments using the Java 2 Standard Edition (J2SE), which has more than 1,500 classes, show that one can recognize inheritance relationships in the proposed representation faster than in the usual textual representation. Consequently the proposed representation can facilitate the understanding of inheritance in visual object-oriented programming environments.

For advanced data-oriented applications in distributed environments, effective information is frequently obtained by integrating or merging various autonomous information sources. There are many problems: how to search information sources, how to resolve their heterogeneity, how to merge or integrate target sources, how to represent information sources with a common protocol, and how to process queries. We have proposed a new language, QUIK, as an extension of a deductive object-oriented database (DOOD) language, QUIXOTE, and extend typical mediator systems. In this paper, we discuss various features of QUIK: programming capabilities as integrating an exchange model and mediator specifications, merging subsumption relations for maintaining consistency, searching alternative information sources by hypothesis generation, and identifying objects.