A distributed computing system consists of heterogeneous computing devices, communication networks, operating system services, and applications. As organisations move toward distributed computing environments, there w...
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A distributed computing system consists of heterogeneous computing devices, communication networks, operating system services, and applications. As organisations move toward distributed computing environments, there will be a corresponding growth in distributed applications central to the enterprise. The design, development, and management of distributed applications presents many difficult challenges. As these systems grow to hundreds or even thousands of devices and similar or greater magnitude of software components, it will become increasingly difficult to manage them without appropriate support tools and frameworks. Further, the design and deployment of additional applications and services will be, at best, ad hoc without modelling tools and timely data on which to base design and configuration decisions. This paper presents a framework for management of distributed applications and systems. The framework is based on a set of common management services that support management activities. The services include monitoring, control, configuration, and data repository services. A prototype system built on the framework is described that implements and integrates management applications providing visualisation, fault location, performance monitoring and modelling, and configuration management. The prototype also demonstrates how various management services can be implemented.
An early version of the Z Standard included the deductive system W for reasoning about Z specifications. Later versions contain a different deductive system. In this paper we sketch a proof that W is relatively sound ...
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ISBN:
(纸本)3540627170
An early version of the Z Standard included the deductive system W for reasoning about Z specifications. Later versions contain a different deductive system. In this paper we sketch a proof that W is relatively sound with respect to this new deductive system. We do this by demonstrating a semantic basis for a correspondence between the two systems, then showing that each of the inference rules of W can be simulated as derived rules in the new system. These new rules are presented as tactics over the the inference rules of the new deductive system.
Knowledge-Based systems (KBS) are developed to contain substantial elements of human knowledge and expertise in a well-defined domain, and use these to support user or expert tasks. Issues related to the social and or...
Knowledge-Based systems (KBS) are developed to contain substantial elements of human knowledge and expertise in a well-defined domain, and use these to support user or expert tasks. Issues related to the social and organisational contexts of these systems are widely acknowledged to be particularly critical to their success. However, methodology proposals usually stop short of adequately handling soft and unstructured data that frame the contexts of use. The handling of qualitative data needs to be done in a way that directly impinges on the wider Knowledge-Based System engineering processes and decisions. In this paper, we discuss the nature of context-sensitive issues, and describe a methodological approach for resolving them through the rigorous analysis of qualitative data, using a methodology which is based upon the Grounded Theory method from the social sciences.
High-level reusability has been achieved in software architecture using design patterns. In this paper, two different applications are presented using design patterns in the system analysis and design cycle. It is con...
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High-level reusability has been achieved in software architecture using design patterns. In this paper, two different applications are presented using design patterns in the system analysis and design cycle. It is concluded that software development using design patterns greatly reduces the design time and reduces the risk of design error.
Use of formal specification does not a priori guarantee correctness. So far a number of animation approaches have been used for validating formal specification correctness. However, they require complex validation pro...
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ISBN:
(纸本)0818682183
Use of formal specification does not a priori guarantee correctness. So far a number of animation approaches have been used for validating formal specification correctness. However, they require complex validation procedures and exhaustive testing and have some intrinsic limitations. On the other hand, formal specification can be validated by showing that certain properties are logical consequences of the specification, which is called formal reasoning or verification. Tool support, in particular an automated theorem prover, is needed for this task. We discuss some experiences in formal specification validation with the automated theorem prover.
In this paper we present a method and a tool for modelling a teletraining session in heterogenous, distributed open environments. We propose a mathematical notion for the training process. Therefore we divide a whole ...
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In this paper we present a method and a tool for modelling a teletraining session in heterogenous, distributed open environments. We propose a mathematical notion for the training process. Therefore we divide a whole training session into presentation units, define some relations on these units and develop a controller for running the session. Units consist of multimedia objects, such as text, graphics, video and audio, which have to be displayed with time and space synchronisation and coordination. In a related project at the department of softwareengineering at the Upper Austria Polytechnic University a tool for modelling and running such teletraining sessions was developed. It is based on the herein defined formalism and compiles well defined unit models into JAVAT/sup TM/ code, which can be executed by usual WEB-Browsers.
We describe the application of model checking tools to analyze a real-time software challenge in the design of Lucent Technologies' 5ESS telephone switching system. We use two tools: COSPAN for checking real-time ...
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ISBN:
(纸本)0897919149
We describe the application of model checking tools to analyze a real-time software challenge in the design of Lucent Technologies' 5ESS telephone switching system. We use two tools: COSPAN for checking real-time properties, and TPWB for checking probabilistic specifications. We report on the feedback given by the tools, and based on our experience, discuss the advantages and the limitations of the approach used.
Although several access control policies can be devised for controlling access to information, all existing authorization models, and the corresponding enforcement mechanisms, are based on a specific policy (usually t...
ISBN:
(纸本)9780897919111
Although several access control policies can be devised for controlling access to information, all existing authorization models, and the corresponding enforcement mechanisms, are based on a specific policy (usually the closed policy). As a consequence, although different policy choices are possible in theory, in practice only a specific policy can be actually applied within a given system. However, protection requirements within a system can vary dramatically, and no single policy may simultaneously satisfy them *** this paper we present a flexible authorization manager (FAM) that can enforce multiple access control policies within a single, unified system. FAM is based on a language through which users can specify authorizations and access control policies to be applied in controlling execution of specific actions on given objects. We formally define the language and properties required to hold on the security specifications and prove that this language can express all security specifications. Furthermore, we show that all programs expressed in this language (called FAM/CAM-programs) are also guaranteed to be consistent (i.e., no conflicting access decisions occur) and CAM-programs are complete (i.e., every access is either authorized or denied). We then illustrate how several well-known protection policies proposed in the literature can be expressed in the FAM/CAM language and how users can customize the access control by specifying their own policies. The result is an access control mechanism which is flexible, since different access control policies can all coexist in the same data system, and extensible, since it can be augmented with any new policy a specific application or user may require.
In our paper, "An analytical model for designing memory hierarchies" (see ibid., vol. 45, no. 10, p. 180-1, 194 (1996)), we made the following statement: "Failing to apply a specific model of workload l...
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In our paper, "An analytical model for designing memory hierarchies" (see ibid., vol. 45, no. 10, p. 180-1, 194 (1996)), we made the following statement: "Failing to apply a specific model of workload locality makes it impossible to provide an easily used, closed-form solution for the optimal cache configuration, and so the results from these papers have contained dependencies on the cache configuration-the number of levels, or the sizes and hit rates of the levels." Our description did not accurately reflect the contents of the paper by J.E. MacDonald and K.L. Sigworth (1975), and we regret any false impressions caused by the inaccuracy.
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