In organizations where duty is around the clock, seven days a week and every week of the year, timetabling is a very difficult task, juggling between the workload and the constraints to be respected. Our work concerns...
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ISBN:
(纸本)3540424210
In organizations where duty is around the clock, seven days a week and every week of the year, timetabling is a very difficult task, juggling between the workload and the constraints to be respected. Our work concerns cyclical timetabling. This is not just duplicating a fixed sequence of assignments, but has to consider fixed annual leave, and various regulations on assignments on successive days. In some cases, the cycle sequence has to be relaxed and cycle length shortened or extended. In other cases, a small change in leave dates is allowed, except in summer. This paper describes the context and the use of work cycles in the real world, proposes an abstract model to take into account the various constraints, and finally shows how to implement an effective solution using constraint logicprogramming (in particular, CHIP V5) to produce timetables of up to 150 people over a yearly horizon.
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...
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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 actually be applied within a given system. In this paper, we present a unified framework that can enforce multiple access control policies within
Methods for mechanically synthesizing concurrent programs from temporal logic specifications have been proposed by Emerson and Clarke and by Manna and Wolper. An important advantage of these synthesis methods is that ...
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Methods for mechanically synthesizing concurrent programs from temporal logic specifications have been proposed by Emerson and Clarke and by Manna and Wolper. An important advantage of these synthesis methods is that they obviate the need to manually compose a program and manually construct a proof of its correctness. A serious drawback of these methods in practice, however, is that they produce concurrent programs for models of computation that axe often unrealistic, involving highly centralized system architecture (Manna and Wolper), processes with global information about the system state (Emerson and Clarke), or reactive modules that can read all of their inputs in one atomic step (Anuchitanukul and Manna, and Pnueli and Rosner). Even simple synchronization protocols based on atomic read/write primitives such as Peterson's solution to the mutual exclusion problem have remained outside the scope of practical mechanical synthesis methods. In this paper, we show how to mechanically synthesize in more realistic computational models solutions to synchronization problems. We illustrate the method by synthesizing Peterson's solution to the mutual exclusion problem.
The proceedings contain 28 papers. The special focus in this conference is on programming Languages and Systems. The topics include: A query language based on the ambient logic;probabilistic polynomial-time process ca...
ISBN:
(纸本)3540418628
The proceedings contain 28 papers. The special focus in this conference is on programming Languages and Systems. The topics include: A query language based on the ambient logic;probabilistic polynomial-time process calculus and security protocol analysis;a systematic approach to static access control;enforcing safety properties using type specialization;semantics and program analysis of computationally secure information flow;programming the web with high-level programming languages;a foundation for three-valued program analysis;entailment with conditional equality constraints;on the complexity of constant propagation;constraint-based type inference for the join-calculus;the recursive record semantics of objects revisited;a formal executable semantics of the javacard platform;proof-directed de-compilation of low-level code;finding duplicated code using program dependences;semantics and termination of simply-moded logic programs with dynamic scheduling and the def-inite approach to dependency analysis.
Brand and Zafiropulo [1] introduced the model of communicating finite-state machines to represent a distributed system connected with FIFO channels. Several different communication protocols can be specified with this...
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We propose a framework for modeling uncertainty where both belief and doubt can be given independent, first-class status. We adopt probability theory as the mathematical formalism for manipulating uncertainty. An agen...
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We propose a framework for modeling uncertainty where both belief and doubt can be given independent, first-class status. We adopt probability theory as the mathematical formalism for manipulating uncertainty. An agent can express the uncertainty in her knowledge about a piece of information in the form of a confidence level, consisting of a pair of intervals of probability, one for each of her belief and doubt. The space of confidence levels naturally leads to the notion of a trilattice, similar in spirit to Fitting's bilattices. Intuitively, the points in such a trilattice can be ordered according to truth, information, or precision. We develop a framework for probabilistic deductive databases by associating confidence levels with the facts and rules of a classical deductive database. While the trilattice structure offers a variety of choices for defining the semantics of probabilistic deductive databases, our choice of semantics is based on the truth-ordering, which we find to be closest to the classical framework for deductive databases. In addition to proposing a declarative semantics based on valuations and an equivalent semantics based on fixpoint theory, we also propose a proof procedure and prove it sound and complete. We show that while classical Datalog query programs have a polynomial time data complexity, certain query programs in the probabilistic deductive database framework do not even terminate on some input databases. We identify a large natural class of query programs of practical interest in our framework, and show that programs in this class possess polynomial time data complexity, i.e. not only do they terminate on every input database, they are guaranteed to do so in a number of steps polynomial in the input database size.
We present first the logic MTL, a real-time temporal logic that is at the heart of the real-time specification language ALBERT. Since this logic is undecidable, we approximate it (using the theory of Abstract Interpre...
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From the Publisher: programming Languages: Principles and Paradigms by Allen Tucker and Robert Noonan is provides balanced coverage of both the principles of language design and the different programming paradigms. T...
ISBN:
(纸本)9780072381115
From the Publisher: programming Languages: Principles and Paradigms by Allen Tucker and Robert Noonan is provides balanced coverage of both the principles of language design and the different programming paradigms. The principles of language design are covered using a formal model and a hands-on laboratory suite that uses a Java interpreter to implement the formal model. This approach gives students an excellent grasp of language design theory and its relationship to practice. It also lays the foundation for the paradigms that are presented in the second half of the book. The text presents and contrasts six major programming paradigms: imperitave,object-oriented,functional,logic,concurrent,and event-driven programming. Through the use of one language for each paradigm,students gain a deep understanding of the paradigm without being distracted by a profusion of languages.
From the Publisher: programming Languages: Principles and Paradigms by Allen Tucker and Robert Noonan is provides balanced coverage of both the principles of language design and the different programming paradigms. ...
ISBN:
(纸本)9780071122801
From the Publisher: programming Languages: Principles and Paradigms by Allen Tucker and Robert Noonan is provides balanced coverage of both the principles of language design and the different programming paradigms. The principles of language design are covered using a formal model and a hands-on laboratory suite that uses a Java interpreter to implement the formal model. This approach gives students an excellent grasp of language design theory and its relationship to practice. It also lays the foundation for the paradigms that are presented in the second half of the book. The text presents and contrasts six major programming paradigms: imperitave,object-oriented,functional,logic,concurrent,and event-driven programming. Through the use of one language for each paradigm,students gain a deep understanding of the paradigm without being distracted by a profusion of languages.
Plato believed in a "pure" reality, where ideas existed in their perfection into eternity. What we perceive as reality, he claimed, is merely a flawed shadow of this ideal world. Many mathematicians find thi...
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ISBN:
(纸本)3540418636
Plato believed in a "pure" reality, where ideas existed in their perfection into eternity. What we perceive as reality, he claimed, is merely a flawed shadow of this ideal world. Many mathematicians find this view appealing since it is precisely this universe of ideas that is the subject of their exploration and discovery. The computer, and more specifically, software, seem perfectly suited to this viewpoint. They allow us to create our own reality, one in which we can simply ignore the underlying physics, forget the tyranny of inertial mass, the drudgery of dealing with machinery that leaks or parts that do not quite fit. But, can we? Even in the ideal world with infinite resources, we have discovered that there are limits to computability. However, the situation with computers and software is much more dire than mere limits on what can be computed. As computers today play an indispensable part of our daily lives we find that more and more of the software in them needs to interact with the physical world. Unfortunately, the current generation of software technologies and practices are constructed around the old Platonic ideal. Standard wisdom in designing software encourages us to ignore the underlying technological platform Ð after all, it is likely to change in a few years anyway Ð and focus exclusively on the program "logic". However, when physical distribution enters the picture, we find that mundane things such as transmission delays or component failures may have a major impact on that logic. The need to deal with this kind of raw physical "stufi" out of which the software is constructed has been relegated to highly specialised areas, such as real-time programming. The result is that we are singularly unprepared for the coming new generation of Internet-based software. Even languages that were nominally designed for this environment, such as Java, are lacking in this regard. For example, it has no facility to formally express that a communication between two
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