4,601,324 research outputs found
Applying Atomicity and Model Decomposition to a Space Craft System in Event-B
No full textEvent-B is a formal method for modeling and verifying consistency of systems. In formal methods such as Event-B, refinement is the process of enriching or modifying an abstract model in a step-wise manner in order to manage the development of complex and large systems. To further alleviate the complexity of developing large systems, Event-B refinement can be augmented with two techniques, namely atomicity decomposition and model decomposition. Our main objective in this paper is to investigate and evaluate the application of these techniques when used in a refinement based development. These techniques have been applied to the formal development of a space craft system. The outcomes of this experimental work are presented as assessment results. The experience and assessment can form the basis for some guidelines in applying these techniques in future cases
Major David Butler letter
No full textThis collection contains a letter written by Major David Butler of the Little Rock Arsenal to General Zachary Taylor at Camp Marcy, Corpus Christi, Texas
Walter Butler to Villers Butler, from Melbourne.
No full textThis record was harvested from a previous catalogue system and will be withdrawn in 2025. Information in this record may be superseded or incomplete. Visit this record in UMA's new catalogue at: https://archives.library.unimelb.edu.au/nodes/view/205159137306
Item: [1963.0020.00018] "Walter Butler to Villers Butler, from Melbourne.
Walter Butler to Kate Butler, from Sale.
No full textThis record was harvested from a previous catalogue system and will be withdrawn in 2025. Information in this record may be superseded or incomplete. Visit this record in UMA's new catalogue at: https://archives.library.unimelb.edu.au/nodes/view/205182137329
Item: [1963.0020.00041] "Walter Butler to Kate Butler, from Sale.
Walter Butler to Villers Butler and to his mother.
No full textThis record was harvested from a previous catalogue system and will be withdrawn in 2025. Information in this record may be superseded or incomplete. Visit this record in UMA's new catalogue at: https://archives.library.unimelb.edu.au/nodes/view/205157137304
Item: [1963.0020.00016] "Walter Butler to Villers Butler and to his mother.
Tasking Event-B: An Extension to Event-B for Generating Concurrent Code
No full textThe Event-B method is a formal approach for modelling systems in safety-, and business-critical, domains. Initially, system specification takes place at a high level of abstraction; detail is added in refinement steps as the development proceeds toward implementation. Our aim has been to develop a novel approach for generating code, for concurrent programs, from Event-B. We formulated the approach so that it integrates well with the existing Event-B methodology and tools. In this paper we introduce a tasking extension for Event-B, with Tasking and Shared Machines. We make use of refinement, decomposition, and the extension, to structure projects for code generation for multitasking implementations. During the modelling phase decomposition is performed; decomposition reduces modelling complexity and makes proof more tractable. The decomposed models are then extended with sufficient information to enable generation of code. A task body describes a task’s behaviour, mainly using imperative, programming-like constructs. Task priority and life-cycle (periodic, triggered, etc.) are also specified, but timing aspects are not modelled formally. We provide tool support in order to validate the practical aspects of the approach
Specification and refinement of discrete timing properties in Event-B
No full textEvent-B is a formal language for systems modeling, based on set theory and predicate logic. It has the advantage of mechanized proof, and it is possible to model a system in several levels of abstraction by using refinement. Discrete timing properties are important in many critical systems. However, modeling of timing properties is not directly supported in Event-B. In this paper we identify three main categories of discrete timing properties for trigger-response pattern, deadline, delay and expiry. We introduce language constructs for each of these timing properties that augment the Event-B language. We describe how these constructs can be mapped to standard Event-B constructs. To ease the process of using the timing constructs in a refinement-based development, we introduce patterns for refining the timing constructs that allow timing properties on abstract models to be replaced by timing properties on refined models. The language constructs and refinement patterns are illustrated through some generic examples. Event-B refinement allows atomic events at the abstract level to be broken down into sub-steps at the refined level. The goal of our refinement patterns is to provide an easy way to represent and correctly refine timing constraints on abstract atomic events with more elaborate timing constraints on the refined events. This paper presents an initial set of patterns
Richard C. Butler Sr. papers
No full textThis collection contains professional, business, and personal files of Richard C. Butler, Sr
Letters from May and June 1950 from Gerald Butler Michael O\u27Connor to Zilla Linford Richards
No full textTwo letters, dated 16 May 1950 and 29 June 1950 from Gerald Butler Michael O\u27Connor at Barnards Mead, Devonshire, England, to Zilla Linford Richards before her planned visi
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