Process algebras with name passing have been proposed for concurrent mobile processes. They can be suitable to describe dynamical changes of connections among processes. To describe mobile communication or mobile computing systems, however, it is necessary to consider locations at which processes run. We propose a description method to design mobile communication systems using a concurrent calculus in this paper. The concept of a field is introduced to model locality of communication. An extension of π-calculus with a field is proposed. The extension does not include locality represented by a field while most related works treat locality within their languages. A field is given when behavior of a target system is verified in a particular environment. The aim of the extension is to verify and to test connectivity between processes under various geographical constraints. This method could be design-oriented in this context. Equivalence relations with/without location in this calculus are also discussed.

We present a topological framework of stepwise specification for concurrent systems in this paper. Some of description techniques can make topologies on the system space. Such topologies corresponds to abstract levels of those description techniques. Using a family of such description techniques, one can specify systems stepwisely. This framework allows to bridge various DTs and modularizing, so that global properties and module properties of systems become to be related to each other. Within this framework, we show derivation of a LOTOS cpecification from temporal logic formulae. An extended version of LOTOS with respect to concurrency is used in this paper. A semantics including concurrency is introduced to do this in this method. The method presented in this paper is applied to mobile telecommunication.

We propose a method which can construct LOTOS specifications of communication systems from temporal properties described in Extended branching time temporal logic (EBTL) in this paper. Description of LOTOS, one of Formal Description Techniques, is based on behaviors of systems so that LOTOS permits strict expression. However, it is difficult to express temporal properties explicitly. On the other hand, Temporal logic is based on properties of systems. Thus temporal logic permits direct expression of temporal properties which can be understood intuitively. Accordingly, temporal logic is more useful than FDTs on the first step of systems specification. This method is effective in this point of view. Specifications obtained using this method can have a structured style. When temporal properties are regarded as constraints about temporal order among actions of systems, those specification can have a constraint oriented style. This method is based on sequential composition of Labelled Transition Systems (LTSs) which are semantics of LOTOS. EBTL is also defined on LTSs. In general, many LTSs satisfy the same temporal property. To obtain such the minimal LTS, the standard form of LTSs corresponding to EBTL operators are defined. Those standard LTSs are mainly tailored to the field of communication protocol. We also show conditions that original temporal properties are preserved in case of sequential composition of standard LTSs. In addition, applying this method to the Abracadabra Protocol, we show that this method can construct specifications of concrete protocols effectively.

In a distributed concurrent system such as a computer communication network, the system components communicate with each other via communication links in order to accomplish a desired distributed application. If the links are dynamically established among the components, the system configuration as well as its behavior becomes complex. In this paper, we give formal specification of such a dynamically reconfigurable system in which the components are modeled by communicating finite state machines executed concurrently with the communication links which are dynamically established and disconnected. We also present an algorithm to validate the safety and link-related properties in the specified behavior. Finally, we design and implement a simulator and a validator that enables execution and validation of the given specification, respectively.