Tomasz Szmuc

UML Statecharts Compositional Semantics in LOTOS

This paper gives an overview of LOTOS-based semantics for compositional UML statecharts. The purpose of this work is to develop a description of a UML statechart model using one of the formal description language - LOTOS.Our approach concentrate on two aspects of the statechart model: concurrency and compositionality. We are using a full LOTOS version to define micro-step semantics which allows to implement cross-state boundaries transitions. Based on the translation function we are able to use a formal statechart model to check the equivalence relations and other model checking techniques.

Decision Tables in Petri Net Models

Many monitoring and control computer systems contain a rule-based system as a part of them. Such a rule based system is used to determine which actions should be taken depending on the data collected from sensors. For both embedded and rule-based systems many different approaches have been proposed, but it is hardly possible to find a formalism that can cope with both of them. The paper deals with a problem of including decision tables into colour Petri net models. A few kinds of decision tables are considered and methods of transformation them into coloured Petri nets form called D-nets are presented. Both non-hierarchical and hierarchical D-nets are considered in the paper.

HTCPNs---Based modelling and evaluation of dynamic computer cluster reconfiguration

An extension of HTCPNs-based software tool for Internet systems modelling and evaluation has been proposed in the paper. After the extension the tool provides new possibilities for modelling and analysis of dynamic cluster reconfiguration algorithm. Some implementation details of the algorithm has been presented. The algorithm has been preliminary assessed by simulation.

Modeling robot behavior with CCL

This paper presents the use of a Concurrent Communicating Lists (CCL) library in robot behavior modeling. CCL provides several software components, which allow the model to be built, simulated and formally verified. Due to the integration with the Robust library the CCL models can be deployed and executed on the actual hardware platforms. Besides the modeling robot behavior, the work also addresses the problem of modeling a robots environment. The CCL models can be verified either formally or by simulation. Since the use of formal methods is always associated with the state explosion problem, the work provides practical guidelines on how to deal with this problem using CCL.

Integrated Approach to Modelling and Analysis using RTCP-nets

RTCP-nets are a subclass of coloured Petri nets formed in order to support specification, design, validation, and verification of embedded systems. The advantages of the nets are directly visible in rapid modelling of the so-called rule-based control systems that are widely applied. A method of embedded systems’ modelling based on RTCP-nets has been presented in the paper. The formalism is supported by software tool called Adder. This tool provides an integrated environment supporting formal specification and design of embedded systems.

HTCPNs: based tool for web-server clusters development

A new software tool for web-server clusters development is presented. The tool consist of a set of predefined Hierarchical Timed Coloured Petri Net (HTCPN) structures - patterns. The patterns make it possible to naturally construct typical and experimental server-cluster structures. The preliminary patterns are executable queueing systems. A simulation based methodology of web-server model analysis and validation has been proposed. The paper focuses on presenting the construction of the software tool and the guidelines for applying it in cluster-based web-server development.

Formal methods — Support or scientific decoration in software development?

The applicability of formal methods to support for software development is discussed in the paper. Software for realtime systems (esp. Safety Critical Systems) is of special interest. Petri nets, Alvis language and temporal logic are examined in which way they may support the development process. Selected approaches for using methods and related examples are discussed to answer the question stated in the title.

Design and Verification of Rule-Based Systems for Alvis Models

Alvis is a modelling language designed for embedded systems that provides a possibility of a formal model verification. Because of the fact that many embedded systems contain a rule-based system as a part of them, it is necessary to provide a possibility to include such systems into Alvis models. Alvis combines flexible graphical modelling of interconnections among agents with a high level programming language used for the description of agents behaviour. The most natural way of including a rule-based system into an Alvis model is to encode it in the Haskell functional language. Some Haskell features like lazy evaluation, pattern matching, high level functions etc. make it a very attractive proposition from the rule-based systems’ engineering point of view. The paper presents a method of encoding and verification of rule-based systems with Haskell to include them into Alvis models.

Modeling UML object event handling with Petri nets

The paper describes method of formal modeling object event handling as it is implemented in UML. The resulted Petri net allows to check UML model properties not only by simulation but also formally. For possibly closest congruence between UML and Petri net model an event queue is defined. Each state machine assigned to an object has its own event queue which is available as long as the machine is. That allows to model not only a simple message passing but also cases, when state machine cannot handle an event. A higher priority of submachines event queue was also taken into consideration. The presented solutions are part of bigger conversion algorithm from UML model to Petri nets. However, the paper was intended to describe the issue in such a detailed way it could be used outside the whole algorithm.