1,354,592 research outputs found
A Basis for feature-oriented modelling in Event-B
No full textFeature-oriented modelling is a well-known approach for Software Product Line (SPL) development. It is a widely used method when developing groups of related software. Due to reuse methods, the development of the software product is quicker, less expensive and of higher quality. However, this approach is not common in formal methods development, which is generally high cost and time consuming, yet crucial in the development of critical systems. We present a method to integrate feature-oriented development with the formal specification language Event-B. Our approach allows the user to map a feature from the feature model to an Event-B component, which contains a formal specification of that feature. We also present some patterns, which assist the user in the modelling of Event-B components. We describe a composition process which consists of the user selecting an instance in the feature model and then constructing this instance in Event-B. While composing, the user may also discharge new composition proof obligations in order to ensure the model is consistent. The model is then constructed using a number of composition rules.<br/
Retrenching partial requirements into system definitions: A simple feature interaction case study
No full textIn conventional model-oriented formal refinement, the abstract model is supposed to capture all the properties of interest in the system, in an as-clutter-free-as-possible manner. Subsequently, the refinement process guides development inexorably towards a faithful implementation. However refinement says nothing about how to obtain the abstract model in the first place. In reality, developers experiment with prototype models and their refinements until a workable arrangement is discovered. Retrenchment is a formal technique intended to capture some of the informal approach to a refinable abstract model in a formal manner that will integrate with refinement. This is in order that the benefits of a formal approach can migrate further up the development hierarchy. The basic ideas of retrenchment are presented, and a simple telephone system feature interaction case study is elaborated. This illustrates not only how retrenchment can relate incompatible and partial models to a more definitive consolidated model during the development of the contracted specification, but also that the same formalism is applicable in a reengineering context, where the subsequent evolution of a system may be partly incompatible with earlier design decisions. The case study illustrates how the natural method of composing retrenchments can give results that are too liberal in certain cases, and stronger laws of composition are derived for systems possessing suitable properties. It is shown that the methodology can encompass more ad hoc and custom built techniques such as Zave’s layered feature engineering approach to applications exhibiting a feature oriented architecture (such as telephony)
The composition of Event-B models
No full textThe transition from classical B [2] to the Event-B language and method [3] has seen the removal of some forms of model structuring and composition, with the intention of reinventing them in future. This work contributes to thatreinvention. Inspired by a proposed method for state-based decomposition and refinement [5] of an Event-B model, we propose a familiar parallel event composition (over disjoint state variable lists), and the less familiar event fusion (over intersecting state variable lists). A brief motivation is provided for these and other forms of composition of models, in terms of feature-based modelling. We show that model consistency is preserved under such compositions. More significantly we show that model composition preserves refinement
Java implementation platform for the integrated state- and event-based specification in PROB
No full textPROB is an animation and model checking tool, which supports integrated event- and state-based specifications combining B and CSP. We present an initial strategy for implementing the combined specification model as a concurrent Java program. Our Java implementation for the combined B and CSP model uses a similar approach to that of JCSP. The restricted operational semantics for the integrated B and CSP model in PROB is defined. Then a new Java package, JCSProB, is developed for implementing the semantics. The new package supports external choice with multi-way synchronization, and introduces an improved multi-threading implementation from JCSP
Timing diagrams add Requirements Engineering capability to Event-B Formal Development
No full textEvent-B is a language for the formal development of reactive systems. At present the RODIN toolkit [15] for Event-B is used for modeling requirements, specifying refinements and doing verification. In order to extend graphical requirements modeling capability into the real-time domain, where timing constraints are essential, we propose a Timing diagram (TD) [13] notation for Event-B. The UML 2.0 based notation provides an intuitive graphical specification capability for timing constraints and causal dependencies between system events. A translation scheme to Event-B is proposed and presented. Support for model refinement is provided. A partial case study is used to demonstrate the translation in practice
A. J. Poppleton
No full textA. J. Poppleton was the chief attorney of the Union Pacific Railroad. Along with John L. Webster, he agreed to represent Standing Bear and the Ponca nation without a fee during Standing Bear's trial
Towards a method for rigorous development of generic requirements patterns
No full textWe present work in progress on a method for the engineering, validation and verification of generic requirements using domain engineering and formal methods. The need to develop a generic requirement set for subsequent system instantiation is complicated by the addition of the high levels of verification demanded by safety-critical domains such as avionics. Our chosen application domain is the failure detection and management function for engine control systems: here generic requirements drive a software product line of target systems. A pilot formal specification and design exercise is undertaken on a small (twosensor) system element. This exercise has a number of aims: to support the domain analysis, to gain a view of appropriate design abstractions, for a B novice to gain experience in the B method and tools, and to evaluate the usability and utility of that method.We also present a prototype method for the production and verification of a generic requirement set in our UML-based formal notation, UML-B, and tooling developed in support. The formal verification both of the structural generic requirement set, and of a particular application, is achieved via translation to the formal specification language, B, using our U2B and ProB tools
Engineering and theoretical underpinnings of retrenchment
No full textRefinement is reviewed, highlighting in particular the distinction between its use as a specification constructor at a high level, and its use as an implementation mechanism at a low level. Some of its shortcomings as a specification constructor at high levels of abstraction are pointed out, and these are used to motivate the adoption of retrenchment for certain high level development steps. Basic properties of retrenchment are described, including a justification of the operation proof obligation, simple examples, its use in requirements engineering and model evolution, and simulation properties. The interaction of retrenchment with refinement notions of correctness is overviewed, as is a range of other technical issues. Two case study scenarios are presented. One is a simple digital redesign control theory problem, and the other is an overview of the application of retrenchment to the Mondex Purse development
Feature composition - towards product lines of event-B models
No full textEvent-B is a formal language for modelling reactive systems, based on set theory and first-order logic. The RODIN toolkit provides comprehensive tool support for modelling and refinement in Event-B, analysis and verification using animator/model-checkers and theorem provers. We consider the need to support reuse, in particular product line reuse, in such a formal development method. Feature modelling is an established technique for reuse in product lines. We introduce concepts of feature modelling and composition in Event-B to support the reuse of formal models and developments. A prototype feature composition tool has been developed (as a RODIN plug-in) for Event-B, based on the Eclipse Modelling Framework (EMF). Using an MDD philosophy, the tool extends the Event-B language meta-model to a composition meta model, and implements prototype composition patterns for Event-B features. Thus, a required composite model can be constructed by selecting, specializing, and composing input features in a defined way. The tool is the first step towards full feature modelling for product line model reuse for Event-B. We describe future work required to meet this goal
Towards an integrated formal method for verification of liveness properties in distributed systems: with application to population protocols
No full textState-based formal methods [e.g. Event-B/RODIN (Abrial in Modeling in Event-B—system and software engineering. Cambridge University Press, Cambridge, 2010; Abrial et al. in Int J Softw Tools Technol Transf (STTT) 12(6):447–466, 2010)] for critical system development and verification are now well established, with track records including tool support and industrial applications. The focus of proof-based verification, in particular, is on safety properties. Liveness properties, which guarantee eventual, or converging computations of some requirements, are less well dealt with. Inductive reasoning about liveness is not explicitly supported. Liveness proofs are often complex and expensive, requiring high-skill levels on the part of the verification engineer. Fairness-based temporal logic approaches have been proposed to address this, e.g. TLA Lamport (ACM Trans Program Lang Syst 16(3):872–923, 1994) and that of Manna and Pnueli (Temporal verification of reactive systems—safety. Springer, New York, 1995). We contribute to this technology need by proposing a fairness-based method integrating temporal and first-order logic, proof and tools for modelling and verification of safety and liveness properties. The method is based on an integration of Event-B and TLA. Building on our previous work (Méry and Poppleton in Integrated formal methods, 10th international conference, IFM 2013, Turku, Finland, pp 208–222, 2013. doi:10.?1007/?978-3-642-38613-8_?15), we present the method via three example population protocols Angluin et al. (Distrib Comput 18(4):235–253, 2006). These were proposed as a theoretical framework for computability reasoning about Wireless Sensor Network and Mobile Ad-Hoc Network algorithms. Our examples present typical liveness and convergence requirements. We prove convergence results for the examples by integrated modelling and proof with Event-B/RODIN and TLA. We exploit existing proof rules, define and apply three new proof rules; soundness proofs are also provided. During the process we observe certain repeating patterns in the proofs. These are easily identified and reused because of the explicit nature of the reasoning
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