Abstract

The productivity and scalability of verifying pipelined circuits can be increased by exploiting the structural and behavioural characteristics that distinguish pipelines from other circuits. This paper presents a formal model of pipelines that augments a state machine with information to describe the transfer of parcels between stages, and reading and writing state variables. Using our model, we created a definition of correctness that is based on the well-established principles of structural, control, and data hazards. We have proved that any pipeline that satisfies our hazards-based definition of correctness is guaranteed to satisfy the conventional correctness statement of Burch-Dill style flushing. Document type: Part of book or chapter of book

Abstract

A joint project of the Austrian company Frequentis1 and the Technical University Graz demonstrates the applicability of executable formal models2. The formal method VDM++ has been applied to specify a safety critical voice communication system (VCS) for air-traffic control. Besides the expected improvement of the informal speciffication documents, 64 defects have been found, the efficiency of the system test-cases to cover the functionality of the VCS has been analyzed. In order to get a test-coverage measure, the formal specification has been animated with existing system test-cases using IFAD’s VDMTools. Document type: Part of book or chapter of book

Abstract

This paper illustrates two different approaches for the application of Formal Methods (FM): integrated-parallel and after-the-fact. In the first approach FMs have been applied integrated and in parallel with structured methods starting from the design phase. In the second approach FMs have been applied after the whole application code had already been developed, before the delivery, to derive an abstract specification of the S/W system and verifY that the most critical properties hold. Both approaches have been adopted in the development of a real application in the domain of the Air Traffic Control, whose purpose is to predict and detect potential air conflicts. The results show that FMs can improve the quality of the software process and products. In particular the accuracy of the final documentation improves and the number of early discovered errors increases. The paper provides general guidelines for the integration of formal and structured methods and presents the documentation outline which has been defined to comment the formal specifications, in the framework of the project applicable standards: 2I67-A military standard and ESA PSS-05-0 and PSS-OI-O. Finally the paper makes an analysis of eight software quality factors, showing also the typology of the discovered errors with the two after-the-fact and integrated-parallel approaches with respect to the traditional development approaches. One conclusion is that FMs provide a real support in developing better quality software, identifYing errors, which sometimes, with traditional approaches, remain undiscovered till and after the software delivery. Document type: Part of book or chapter of book

Abstract

Open Distributed Processing (ODP) is a framework for specifying open distributed systems, under development by the International Standards Organisation (ISO). It is based on the general idea of viewpoints - i.e. partial specifications of an overall system, from different perspectives - but assumes five specific, named viewpoints, which are described informally in the ODP Reference Model (RM-ODP). This paper summarises some observations regarding an attempt to use ODP to specify a complex air traffic control system. Some of the key issues that arise are discussed further in the context of the formal specification of a simpler, idealised model, involving two formalised viewpoints - the Information Viewpoint (a high-level, abstract specification, in Z), and the Computational Viewpoint (a specification of distributed components and objects, in Object-Z). Document type: Book

Abstract

The design of large-scale complex systems requires their analysis from multiple perspectives, often through the use of requirements models. Diversely located experts with different backgrounds (e.g., safety, security, performance) create such models using different requirements modeling languages. One open challenge is how to align these models such that they cover the same parts of the domain. We propose a technique based on natural language processing (NLP) that analyzes several models included in a project and provides suggestions to modelers based on what is represented in the models that analyze other concerns. Unlike techniques based on meta-model alignment, ours is flexible and language agnostic. We report the results of a focus group session in which experts from the air traffic management domain discussed our approach.

Abstract

International audience; The Internet of Things (IoT) consists in connecting every aspect of daily and professional life to a common infrastructure, in order to improve considerably the efficiency of otherwise unthinking objects. The huge scale on which they operate, as well as the lack of adequate standards and infrastructures makes the development of IoT applications a task of gradually growing complexity. The objective of this work is to define a formal model with BiAgents (Bigraphical Agents) for IoT applications, based on a suggested generic multi-layered architecture. We show how bigraphs support the structural aspects modelisation of these applications while the agents specify their analytical and decisional aspects. We proceed then to the edition and execution of our model using the bigraph implementation tool (RCTool4 Bigraphs), and through the exploitation of its model-checker, we formally verify its most critical property. As a practical example, we study the case of a Collision Avoidance System.