Tony Modica

Petri Net Transformations

Abstract Petri Nets: A Uniform Approach and Rule-Based Refinement. PhD thesis, Technical University Berlin, 1996. Shaker Verlag. [23] J. Padberg. Categorical Approach to Horizontal Structuring and Refinement of High-Level Replacement Systems. Applied Categorical Structures, 7(4):371-403, 1999. [24] J. Padberg. Basic Ideas for Transformations of Specification Architectures. In Proc.Workshop on Software Evolution through Transformations (SET 02), volume 74 of ENTCS, 2002. [25] J. Padberg, H. Ehrig, and L. Ribeiro. Algebraic High-Level Net Transformation Systems. Mathematical Structures in Computer Science, 5(2):217-256, 1995. [26] J. Padberg, P. Schiller, and H. Ehrig. New Concepts for High-Level Petri Nets in the Application Domain of Train Control. In Proc. Symposium on Transportation Systems, pages 153-160, 2000. [27] J. Padberg and M. Urbasek. Rule-Based Refinement of Petri Nets: A Survey. In Proc. Petri Net Technology for Communication-Based Systems, volume 2472 of LNCS, pages 161-196. Springer, 2003. [28] W. Reisig. Petri Nets and Algebraic Specifications.

Independence Analysis of Firing and Rule-based Net Transformations in Reconfigurable Object Nets

The main idea behind Reconfigurable Object Nets (RONs) is to support the visual specification of controlled rule-based net transformations of place/transition nets (P/T nets). RONs are high-level nets with two types of tokens: object nets (place/transition nets) and net transformation rules (a dedicated type of graph transformation rules). Firing of high-level transitions may involve firing of object net transitions, transporting object net tokens through the high-level net, and applying net transformation rules to object nets, e.g. to model net reconfigurations. A visual editor and simulator for RONs has been developed as a plug-in for ECLIPSE using the ECLIPSE Modeling Framework (EMF) and Graphical Editor Framework (GEF) plug-ins. The problem in this context is to analyze under which conditions net transformations and token firing can be executed in arbitrary order. This problem has been solved formally in a previous paper. In this contribution we present an extension of our RON tool which implements the analysis of conflicts between parallel enabled transitions, between parallel applicable net transformation rules (Church-Rosser property), and between transition firing and net transformation steps. The conflict analysis is applied to a RON simulating a distributed producer-consumer system.

Formal Modeling of Communication Platforms using Reconfigurable Algebraic High-Level Nets

Communication nowadays is based on communication platforms like Skype, Facebook, or SecondLife. The formal modeling and analysis of communication platforms poses considerable challenges, namely highly dynamic structures and complex behavior. Since most of the well-known formal modeling approaches are adequate only for specific aspects of communication platforms, in this paper we introduce the approach of reconfigurable algebraic high-level nets with individual tokens and show in our case study Skype that this approach is adequate for modeling the main aspects and features of communication platforms.

Towards Translating Graph Transformation Approaches by Model Transformations

Recently, many researchers are working on semantics preserving model transformation. In the field of graph transformation one can think of translating graph grammars written in one approach to a behaviourally equivalent graph grammar in another approach. In this paper we translate graph grammars developed with the GROOVE tool to AGG graph grammars by first investigating the set of core graph transformation concepts supported by both tools. Then, we define what it means for two graph grammars to be behaviourally equivalent, and for the regarded approaches we actually show how to handle different definitions of both - application conditions and graph structures. The translation itself is explained by means of intuitive examples.

Modeling multicasting in communication spaces by reconfigurable high-level Petri nets

In this paper, we extend this previous work on recon-figurable Petri nets on the one hand by marking-changing Petri net transformations, and on the other hand by a technique parallelizing the application of net transformation rules at several matches at once. Both extensions together allow a flexible modeling of communication concepts in communication spaces, like e.g. multicasting, where one actor transmits contents to a group of selected actors. We apply our extended technique to model multicasting group communication in the Internet telephone system Skype.

Implementing Petri Net Transformations using Graph Transformation Tools

Petri net transformations have been defined formally in the abstract framework of adhesive HLR categories, which allows rule-based rewriting of graph- like structures, similar to graph transformation. In this paper we discuss differences between Petri net rewriting and graph rewriting which makes it necessary to add checks and conditions when implementing Petri net transformations using an exist- ing graph transformation tool like AGG. The extensions concern the preservation of Petri net transition firing behavior and the mapping of markings. As a running example, we present the RON environment, a visual editor, simulator and net trans- formation tool for reconfigurable Petri nets which has been developed as a plug-in for ECLIPSE based on the graph transformation engine AGG.

Formal modeling and analysis of communication platforms like skype based on Petri net transformation systems

The aim of this PhD thesis is to use an extension of Petri nets and Petri net transformation systems called AHOI nets in order to allow formal modeling and analysis of communication platforms (CP) like Skype. In the following, we explain the main ideas of AHOI nets and discuss how they can be used to model features of Skype. We give an overview of results achieved so far and remaining open problems to be solved in this PhD thesis.