Hussein S. M. Zedan

A specification-oriented semantics for the refinement of real-time systems

A refinement calculus for the development of real-time systems is presented. The calculus is based upon a wide-spectrum language called the temporal agent model (TAM), within which both functional and timing properties can be expressed in either abstract or concrete terms. A specification-oriented semantics for the language is given. Program development is considered as a refinement process, i.e. calculation of a structured program from an unstructured specification. A calculus of decomposition is defined. An example program is developed.

TAM: A Formal Framework for the Development of Distributed Real-Time Systems

The Temporal Agent Model (TAM) is a wide-spectrum development language for real-time systems. In TAM, limited resources are modelled by deriving release times and absolute deadlines from weakest pre-condition predicate transformers. In this paper the language syntax and semantics are described along with a number of examples.

A distributed algorithm for distributed termination

Abstract We improve on Ranas distributed and fully symmetric solution for detection of distributed termination.

Lucinda - A Polymorphic Linda

This document describes the courting of Linda (a coordination language) by Russell (a computation language), and the subsequent conception of their child Lucinda. Mother and baby are both doing well.

Congruent weak bisimulation with dense real-time

Abstract New definitions for connectives in a real-time process algebra are introduced, for which the natural weak bisimulation relation is a congruence. Two kinds of weak bisimulation can be distinguished: step and path bisimulation.

Weakest precondition semantics for time and concurrency

Abstract A weakest precondition semantics for a real-time concurrent language is defined. An example in verification is presented, and the use of predicate transformers as the basis of a refinement calculus is also discussed.

Lucinda—an overview

This document describes the courting of Linda (a coordination language) by Russell (a computation language), and the subsequent conception of their child Lucinda. Mother and baby are both doing well.A number of disadvantages with current Linda implementations are discussed, and a new language, Lucinda, is proposed to overcome them. Lucinda provides multiple, typed tuple spaces, polymorphism, and a novel approach to data structuring and storage.

On guaranteeing hard real-time tasks

Abstract The development of complex real-time systems has become a reality with the move from uniprocessor to distributed systems. In general, these systems require adaptability in order to cope with many types of timing constraints. The most critical part in the development of these systems is the scheduler. Our approach is based on the view that if the system is adaptable then the reliability is easier to be attained. We are proposing the use of milestone notion within the Least Laxity Scheduler Algorithm and augmenting it with an “alert” mechanism that is generated using the information provided by the milestone. The scheduler is fully implemented in an industrially available kernel namely RTXC/MP1

A Predicative Semantics for the Refinement of Real-Time Systems

A formal framework for a calculus of real-time systems is presented. Specifications and program statements are combined into a single language called TAM (the Temporal Agent Model), that allows the user to express both functional and timing properties. A specification-oriented semantics for TAM is given, along with the definition of a refinement relation and a calculus which is sound with respect to that relation. A simple real-time program is also developed using the calculus.

PCHAN: a notion for dynamic resource management in distributed occam systems

Abstract PCHAN (Priority CHANnel) is a new notion for resource management in the design of distributed occam systems. The concept itself effectively redefines the usual idea of “priority”. Priority usually refers to the relative importance of access to the SAME resource. In this paper, the client is requesting different services from the same manager, and priority defines the relative importance of those services. PCHAN permits dynamic resource allocation by allowing clients to (dynamically) vary their priorities. The notion is introduced within the framework of occams model of computations and illustrated using various programming paradigms.