The ever-growing popularity of the Internet is dramatically changing the landscape of the communications marketplace. The two separate worlds of the Internet and Telecommunications are converging. The respective advantages of the two environments are being integrated to fulfill the promise of the information super-highways. In this paper, we examine the impact of the Internet on the main telecommunication architectures, namely the IN, the TMN and TINA. There are two new tendencies for implementing telephony services in combination with the Internet: running part of the control system over the Internet, or conveying both the user data and the control information over the Internet. We examine these two tendencies, and elaborate on possible ways of salvaging the best parts of the work achieved by the TINA-Consortium in the Internet context. q

Based on the notion of event-based behavioral abstraction (EBBA) we specify properties of object-oriented distributed systems in linear time temporal logic. These properties are then observed at system run-time and it is checked whether or not the system violates the specified behavioral constraints. In our approach, several steps in the testing process can be automized: instrumenting the source code, constructing test-oracles and generating an observer. Taking an industrial example as basis, we discuss how our proposal can be integrated into the software design-and testing process.

The Producer/Comumer (P/C) has been used to model communication in networks. The modei states that in a q s e m there is a producer of a given informution and one or more consumers o f this information With this model dzflerenf kinds of communication failures may occuz In this paper; with the help ofthe adapted Jynchronous model (ASM), we show two methods for formally verifiing the n e c e s s q conditiom to avoid bufer overwrites in the P/C model. Spec@calIy, we aplore the constraints on communication parameters in distributed periodic control and more generally, we demonstrate how behavioral properties can be analyzed using formal methods. B INTRODUCTIQNFieldbusses are real-time Iocal area networks that have been designed to ensure communications at the process level. They are often used to transport input data &om a manufacturing process to controllers and output data back to the process. Designs must take into account the delays introduced by fieldbusses since these delays, and variation them, can deteriorate the quality and correctness of control. It is important to be able to study and verify the limitations on the upper and lower bounds of these time-varying delays to be able to guarantee a certain quality of control and predictable behavior. We shall focus on two types of delay -computation and communication delay -in a producer/consumer model (P/C) with periodic behavior. To this end, we will explore how to formally represent a periodic PIC based on the adapted synchronous model (ASM), a useful abstraction of the computation and communication tasks of periodic applications.More generally, we are interested in applying two different approaches of specification and verification of properties of distributed real-time control applications. Both approaches allow the synthesis of a formal representation which provides us with a nonambiguous description of the computation and communication aspects of applications with periodic behavior (e.g., applications such as control and command systems distributed over a fieldbus network). Both formal models extend the applicability ofthe synchronous model describing how distributed processors perfom computations in a synchronous manner (they perform in a lock-step fashion), and how the communication medium is synchronous (message delivery within a bounded delay).Organization. The paper will be organized as follows. After this introduction we present the synchronous model in nonformal terms, and the principal characteristics and parameters it defines for representing computation and communication.We also present some of the properties that applications corresponding to the informal model should have (ie. sufficient conditions on timing which guarantee that communication overwrites do not occur). The next two sections show how the informal description is formalized. In the first case we use the synchronous language ESTEFEL, and in the second case we use stockmfic timed petri nets. For both representations we discuss how to verify properties dealing with the timely sending a...

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This paper addresses the problems concerning the faulttolerant distributed replication of a controlling application in an automated system. The Manufacturing Message Specificafion ( M M S ) is used as a communication protocol between the controlling application ( M M S client) and the automated industrial equipment (MMS servers). A distribufed systems toolkif @ST) is used to manage the replication of the controlling application. We identify potential obstacles in the MMS environment when passive client replication is used. We suggest methods that the recovering client can use to overme these obstacles. The solutions and alternatives proposed are discussed with respect to their conformance to tbe MMS standard.