We show how the Hindley/Milner polymorphic type system can be extended to incorporate overloading and subtyping. Our approach is to attach constraints to quantified types in order to restrict the allowed instantiation...
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We show how the Hindley/Milner polymorphic type system can be extended to incorporate overloading and subtyping. Our approach is to attach constraints to quantified types in order to restrict the allowed instantiations of type variables. We present an algorithm for inferring principal types and prove its soundness and completeness. We find that it is necessary in practice to simplify the inferred types, and we describe techniques for type simplification that involve shape unification, strongly connected components, transitive reduction, and the monotonicities of type formulas.
the proceedings contains 72 papers. Topics discussed include computer applications in manufacturing, process planning, inventory and materials control, knowledge based systems, softwareengineering, quality management...
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ISBN:
(纸本)0444815988
the proceedings contains 72 papers. Topics discussed include computer applications in manufacturing, process planning, inventory and materials control, knowledge based systems, softwareengineering, quality management, decision support systems and optimization techniques.
In this paper we introduce a new approach for parallel, distributed simulation of modular, hierarchical DEVS and DEVS-based combined discrete/continuous multiformalism models. the algorithm combines conservative and o...
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ECOSIM, a software tool for the simulation of ECLSS which has been developed for the European Space Agency (ESA), provides a powerful, friendly graphical interface to users. To test and verify the evolutional capabili...
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computersystems are increasingly employed in circumstances where their failure (or even their correct operation, if they are built to flawed requirements) can have serious consequences. there is a surprising diversit...
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computersystems are increasingly employed in circumstances where their failure (or even their correct operation, if they are built to flawed requirements) can have serious consequences. there is a surprising diversity of opinion concerning the properties that such critical systems' should possess, and the best methods to develop them. the dependability approach grew out of the tradition of ultra-reliable and fault-tolerant systems, while the safety approach grew out of the tradition of hazard analysis and system safety engineering. Yet another tradition is found in the security community, and there are further specialized approaches in the tradition of real-time systems. In this article are examined the critical properties considered in each approach, and the techniques that have been developed to specify them and to ensure their satisfaction. Since systems are now being constructed that must satisfy several of these critical system properties simultaneously, there is particular interest in the extent to which techniques from one tradition support or conflict withthose of another, and in whether certain critical system properties are fundamentally compatible or incompatible with each other. As a step toward improved understanding of these issues, it is suggested that a taxonomy, based on Perrow's analysis (Perrow, C. Normal Accidents: Living with High Risk Technologies. Basic Books, New York, 1984), that considers the complexity of component interactions and tightness of coupling as primary factors, is used.
this paper describes a user-friendly computer program containing an approach for the prediction of extreme wave climates based on the extrapolation of the scatter diagram of significant wave height Hs and mean zero-up...
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this paper describes a user-friendly computer program containing an approach for the prediction of extreme wave climates based on the extrapolation of the scatter diagram of significant wave height Hs and mean zero-upcrossing period Tz. Following the validity tests of data input, the computer program takes into account the existence of missing data and calms and includes routines for the treatment of various theoretical descriptions of Hs. Sensitivity studies have been completed to appraise the changes in wave predictions due to missing data considered either as calms or instrument failure and due to inadequacies of measurement systems to record low Tz values. the possible influence of currents on extreme wave height predictions has also been taken into account. For example purposes, the computer program is used for the prediction of extreme wave heights in a location (Morecambe Bay, UK) where wave data (scatter diagrams) are available.
HYDROSCOPE is a Greek nation-wide research programme with 14 participating organisations aiming at the development of a national distributed database system for meteorological, hydrological and hydrogeological informa...
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HYDROSCOPE is a Greek nation-wide research programme with 14 participating organisations aiming at the development of a national distributed database system for meteorological, hydrological and hydrogeological information. Available modern computer technologies such as powerful workstations, high speed wide-area networks, relational distributed database management systems, client-server architecture, graphical user interfaces and fourth generation programming languages have been used throughout the project. In parallel, a human network consisting of scientists and engineers from all participating organisations, universities, ministries, research centres and public agencies, has been set up. In this paper we present the two-year experience from the project, both at technical and human level, the achievements made and the problems encountered, as well as the perspectives up to the year 2000.
In fault-tolerant real-time systems, software errors can be detected, recovered from, and reported using a recovery controller. A simulator has been developed to test the performance of an ANN (Artificial Neural Netwo...
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ISBN:
(纸本)0819415472
In fault-tolerant real-time systems, software errors can be detected, recovered from, and reported using a recovery controller. A simulator has been developed to test the performance of an ANN (Artificial Neural Network) based recovery controller. the simulator for a highly reliable, fault-tolerant multiprocessor telecommunications exchange provides a real-world application to test the effectiveness of the ANN recovery controller. the ANN provides the software recovery controller withthe adaptability to determine recovery actions for faults that were previously unseen or not anticipated. this reduces the number of times that human intervention is required to recover the system, and thus reduces the total down-time for the system. the ANN is trained by inserting known faults into the simulated real-time system. the system collects data on the characteristics observed when the fault is detected and uses the back propagation learning algorithm to classify the observed characteristics and recent history of recovery actions into an appropriate recovery action such as restarting or terminating a process, initializing the operating system for a specific processor, or reloading a data base for a processor of group of processors. Once the neural network has been trained, it is used to determine the appropriate responses for faults that occur during the operation of the system.
this paper describes some basic issues and requirements for software structure of distributed CIM systems. Such systems have a wide applicability, especially in the context of geographically distributed manufacturing ...
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this paper presents a new approach for improving performance of instruction cache based systems. the idea is to prevent cache misses caused when different segments of code, which are executed in the same loop, are map...
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