Tommaso Bolognesi

Introduction to the ISO specification language LOTOS

LOTOS is a specification language that has been specifically developed for the formal description of the OSI (Open Systems Interconnection) architecture, although it is applicable to distributed, concurrent systems in general. In LOTOS a system is seen as a set of processes which interact and exchange data with each other and with their environment. LOTOS is expected to become an ISO international standard by 1988.

A Consistent Causality-Based View on a Timed Process AlgebraIncluding Urgent Interactions

This paper discusses a timed variant of a process algebra akin to LOTOS, baptized UPA, in a causality-based setting. Two timed features are incorporated—a delay function which constrains the occurrence time of atomic actions and an urgency operator that forces (local or synchronized) actions to happen urgently. Timeouts are typical urgent phenomena. A novel timed extension of event structures is introduced and used as a vehicle to provide a denotational causality-based semantics for UPA. Recursion is dealt with by using standard fixpoint theory. In addition, an operational semantics is presented based on separate time- and action-transitions that is shown to be consistent with the event structure semantics. An interleaving semantics for UPA is immediately obtained from the operational semantics. By adopting this dual approach the well-developed timed interleaving view is extended with a consistent timed partial order view and a comparison is facilitated of the partial order model and the variety of existing (interleaved) timed process algebras.

Correctness Preserving Transformations for the Early Phases of Software Development

The Lotosphere methodology is meant to support system designers and implementors along the trajectory from an initial, abstract specification, down to concrete design and implementation: the latter should be obtained from the former via a disciplined sequence of transformation and refinement steps.

G-LOTOS: a graphical language for concurrent systems

Abstract This paper introduces G-LOTOS, a graphical language for the formal specification of concurrent systems. More precisely, G-LOTOS is a graphical syntax for the Formal Description Technique LOTOS, which is an ISO international standard. This paper requires no familiarity with LOTOS and can also be used as a first approach to the language. G-LOTOS is intended to provide a better readability and more intuitive understanding of formal specifications than textual LOTOS, and is itself being standardised in a joint ISO/CCITT effort. The introduction to the graphical syntax is supported by several short examples, by a complete G-LOTOS specification, and by a LOTOS/G-LOTOS conversion table.

The definition of a graphical G-LOTOS editor using the meta-tool LOGGIE

Abstract We present a prototype implementation of a graphical editor for a subset of G-LOTOS. The graphical G-LOTOS syntax is being standardized within ISO for the LOTOS specification language. First, we provide a formal definition of the G-LOTOS subset. Then, the specification of the editor is derived from this formal definition. Finally, such a specification is used for the automatic generation of the editor by means of the LOGGIE meta-tool.

Formal Methods for Distributed System Development

This paper describes the fonnal verification of a fault-tolerant group membership algorithm that constitutes one of the central services of the Time-Triggered Protocol (TTP). The group membership algorithm is formally specified and verified using a diagrammatic representation of the algorithm. We describe the stepwise development of the diagram and outline the main part of the correctness proof. The verification has been mechanically checked with the PVS theorem prover.

Composing Event Constraints in State-Based Specification

Event-based process algebraic specification languages support an elegant specification technique by which system behaviours are described as compositions of constraints on event occurrences and event parameters. This paper investigates the possibility to export this specification paradigm to a state-based formalism, and discusses some deriving advantages in terms of verification.

Non-standard Interpretations of LOTOS Specifications

Non-standard interpretations of LOTOS specifications are proposed as a most convenient and conservative way to extend the expressivity of the language without affecting its standard syntax and transition-system-based semantics. Some simple non-standard interpretations, alse called view functions, are introduced. Two different styles of formal definition are adopted (denotational and operational) for providing, respectively, a refinement of the standard LOTOS process functionality parameter, and a new parameter measuring the degree of synchronization exhibited by a specification.

Erratum to: Formal Methods for Distributed System Development

Erratum to: Tommaso Bolognesi and Diego Latella (Eds.) Formal Methods for Distributed System Development DOI: 10.1007/978-0-387-35533-7