The author describes a semiformal process model for technology transfer at Ferranti computersystems. Experience has shown that satisfactory transition takes place only when staff members move from one group to the ne...
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ISBN:
(纸本)0818620269
The author describes a semiformal process model for technology transfer at Ferranti computersystems. Experience has shown that satisfactory transition takes place only when staff members move from one group to the next either with the technology or with the problem.< >
One of the primary concerns in developing computer embedded safety-critical systems is how to develop quality software. software must fulfill its functional requirements and must not contribute to the violation of saf...
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ISBN:
(纸本)0818685972
One of the primary concerns in developing computer embedded safety-critical systems is how to develop quality software. software must fulfill its functional requirements and must not contribute to the violation of safety properties of the entire system. To this end, capturing error free and satisfactory functional requirements is crucial before proceeding to the subsequent development phases. We describe an approach to specifying and verifying software for safety-critical systems with the practical formal method SOFL (Structured-Object-based-Formal Language). Requirements specification focuses on the functionality of the software, but with the consideration of safety constraints and its interaction with the surrounding operational environment. The verification of specifications can be carried out using three techniques: da ta flow reachability checking, specification testing, and rigorous proofs, respectively. We apply this approach to a realistic railway crossing controller for a case study and analyzes its result.
General synthesis methods for efficiently implementing self-timed combinational logic (CL) and finite-state machines (FSM) are presented. The resulting CL is shown to require fewer gates than other proposed methods. T...
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ISBN:
(纸本)0818620412
General synthesis methods for efficiently implementing self-timed combinational logic (CL) and finite-state machines (FSM) are presented. The resulting CL is shown to require fewer gates than other proposed methods. The FSM is implemented by interconnecting a CL module with a self-timed master-slave regime. Alternate FSM synthesis methods are also considered. A formal system of behavioral sequential constraints is presented for each of the systems, and their behavior is proven correct. Thus, the synthesized CLs and FSMs can serve as correct-by-construction building blocks for self-timed silicon system compilation.
This paper presents the Architecture Tradeoff Analysis Method (ATAM), a structured technique for understanding the tradeoffs inherent in the architectures of software-intensive systems. This method was developed to pr...
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ISBN:
(纸本)0818685972
This paper presents the Architecture Tradeoff Analysis Method (ATAM), a structured technique for understanding the tradeoffs inherent in the architectures of software-intensive systems. This method was developed to provide a principled way to evaluate a software architecture's fitness with respect to multiple competing quality attributes: modifiability, security, performance, availability, and so forth. These attributes interact-improving one often comes at the price of worsening one or more of the others-as is shown in the paper, and the method helps us to reason about architectural decisions that affect quality attribute interactions. The ATAM is a spiral model of design: one of postulating candidate architectures followed by analysis and risk mitigation, leading to refined architectures.
Resource scheduling in distributed systems aims at achieving maximal system performance by utilizing the available system resources efficiently. Large distributed systems, comprising hundreds or thousands of nodes and...
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ISBN:
(纸本)0818681365
Resource scheduling in distributed systems aims at achieving maximal system performance by utilizing the available system resources efficiently. Large distributed systems, comprising hundreds or thousands of nodes and spanning vast geographical distances (e.g. Internet), require resource scheduling to be scalable. Scalability has become a common requirement in the design and development of distributed software. This paper describes a comprehensive approach to software development, leading from the stage of requirements specification, through design and algorithm assessment to a prototype implementation of a scalable resource scheduling policy. Scalability is achieved by system partitioning. Communication delays may limit scalability and degrade system performance. In this work, delays are handled to improve the performance of a scheduling policy. The paper demonstrates performance results obtained in simulation under communication and computation overload conditions. The simulation code is later used for prototype implementation. Finally, we examine the software design issues and applicability of the prototype to different distributed environments, providing the example of PVM [7].
Highlights are presented of the visual notation MachineCharts and the corresponding architectural design method. The approach has its roots in Buhr diagrams for Ada, but is both deeper than Buhr diagrams and wider in ...
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ISBN:
(纸本)0818620412
Highlights are presented of the visual notation MachineCharts and the corresponding architectural design method. The approach has its roots in Buhr diagrams for Ada, but is both deeper than Buhr diagrams and wider in scope than Ada. Relationships to current tools are identified. The primary objectives were to provide human designers with means of (1) building confidence in the robustness of their designs for reactive systems, by exploring them visually in the (time, place) domain in powerful ways, and (2) making design thinking portable between different implementation technologies.
This paper examines the reciprocal influence of method, process and tool as evidenced in a case study in which a requirements management method and process were defined, evolved and applied on projects. Although a too...
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The authors focus on two modes of operation, namely, rational and experimental, and on two means of expression, namely, specifications and prototypes, as key features of approaches to software design. The discussion i...
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ISBN:
(纸本)0818620412
The authors focus on two modes of operation, namely, rational and experimental, and on two means of expression, namely, specifications and prototypes, as key features of approaches to software design. The discussion is based on an examination of relevant trends in software development and on reappreciation of well-known principles of human problem-solving. They conclude that the effectiveness of a design effort is restricted by what they we call the principle of limited reduction: relying on rational behavior to reduce complexity introduces new sources of uncertainty and this requires experimental countermeasures. Correspondingly, relying on experimental behavior to reduce uncertainty introduces new sources of complexity requiring rational countermeasures. One important implication of this principle is that effective software design requires a systematic effort combining rational and experimental modes of operation, independently of whether specifications or prototypes are used.
Robot systems are an archetype of complex process control systems where valid production programs may have any number (>2) of process commands, which are difficult to optimize with classical methods. Robot trajecto...
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ISBN:
(纸本)0818620412
Robot systems are an archetype of complex process control systems where valid production programs may have any number (>2) of process commands, which are difficult to optimize with classical methods. Robot trajectories can be programmed automatically by a genetic algorithm providing the algorithm will consider the order and varying lengths of trajectories. A genetic, adaptive, heuristic algorithm which is designed to optimize robot trajectories is described. Though the model presented is a general model for redundant structures and could represent any n-link structures, it was applied to a 3-link structure. The performance of the genetic algorithm show characteristic improvements when compared with that of a hill-climb and a random search algorithm.
The EEM (Effort Estimation Model) for software development is a support system to assist in the process of economic evaluation of software projects that takes place when a project is about to start. At that point the ...
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ISBN:
(纸本)0818620412
The EEM (Effort Estimation Model) for software development is a support system to assist in the process of economic evaluation of software projects that takes place when a project is about to start. At that point the estimates are done only at a low level of precision, to enable the management to determine project feasibility. The EEM uses techniques consistent with the level of knowledge generally available in the organization at that time. Estimates for the effort required at the later stages of the software development life cycle are done in a detailed form, using differential techniques, towards the end of the requirement analysis and the preliminary design stages. Different estimating approaches can be used at the different points in the system development process. A prototype was developed based on these principles and has been working for the last 18 months. This report discusses the underlying assumptions, concepts and process involved.
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