Mostrando recursos 141 - 160 de 5.033

  1. An Open-Source and Declarative Approach Towards Teaching Large-Scale Networked Systems Programming

    Saeed, Taher; Gill, Harjot; Fei, Qiong; Zhang, Zhuoyao; Loo, Boon Thau
    This paper describes our experiences at the University of Pennsylvania in developing course projects for a large advanced undergraduate and first year graduate course in networked systems. Students work in teams to develop substantial networked systems programming projects (>10000 lines of code) using network simulator 3 (ns-3), an emerging open-source network simulator that is aimed at replacing the popular ns-2 simulator. Projects are developed in layers, where students build upon earlier assignments, first developing a protocol for Internet Protocol (IP) routing, followed by a distributed hash table (DHT) overlay network, and finally, a keyword-based search engine. One novelty of our...

  2. Hardware/Software Organization of a High Performance ATM Host Interface

    Traw, C. Brendan S; Smith, Jonathan M
    Concurrent increases in network bandwidths and processor speeds have created a performance bottleneck at the workstation-to-network host interface. This is especially true for BISDN networks where the fixed length ATM cell is mismatched with application requirements for data transfer; a successful hardware/software architecture will resolve such differences and offer high end-to-end performance. The solution we report carefully splits protocol processing functions into hardware and software implementations. The interface hardware is highly parallel and performs all per-cell functions with dedicated logic to maximize performance. Software provides support for the transfer of data between the interface and application memory, as well as the...

  3. Constructive Logics Part I: A Tutorial on Proof Systems and Typed Lambda-Calculi

    Gallier, Jean H
    The purpose of this paper is to give an exposition of material dealing with constructive logic, typed λ-calculi, and linear logic. The emergence in the past ten years of a coherent field of research often named "logic and computation" has had two major (and related) effects: firstly, it has rocked vigorously the world of mathematical logic; secondly, it has created a new computer science discipline, which spans from what is traditionally called theory of computation, to programming language design. Remarkably, this new body of work relies heavily on some "old" concepts found in mathematical logic, like natural deduction, sequent calculus,...

  4. What's So Special About Kruskal's Theorem and the Ordinal To? A Survey of Some Results in Proof Theory

    Gallier, Jean H
    This paper consists primarily of a survey of results of Harvey Friedman about some proof theoretic aspects of various forms of Krusal's tree theorem, and in particular the connection with the ordinal Ƭo. We also include a fairly extensive treatment of normal functions on the countable ordinals, and we give a glimpse of Veblen Hierarchies, some subsystems of second-order logic, slow-growing and fast-growing hierarchies including Girard's result, and Goodstein sequences. The central theme of this paper is a powerful theorem due to Kruskal, the "tree theorem", as well as a "finite miniaturization" of Kruskal's theorem due to Harvey Friedman. These...

  5. Coherence and Consistency in Domains (Extended Outline)

    Gunter, Carl A; Jung, Achim
    Almost all of the categories normally used as a mathematical foundation for denotational semantics satisfy a condition known as consistent completeness. The goal of this paper is to explore the possibility of using a different condition - that of coherence - which has its origins in topology and logic. In particular, we concentrate on those posets whose principal ideals are algebraic lattices and whose topologies are coherent. These form a cartesian closed category which has fixed points for domain equations. It is shown that a "universal domain" exists. Since the construction of this domain seems to be of general significance,...

  6. Verifiable Policy-Based Routing With DRIVER

    Wang, Anduo; Liu, Changbin; Loo, Boon Thau; Sokolsky, Oleg; Basu, Prithwash
    The Internet today runs on a complex routing protocol called the Border Gateway Protocol (BGP). BGP is a policy-based protocol, in which autonomous Internet Service Providers (ISPs) impose their local policies on the propagation of routing information. Over the past few years, there has been a growing consensus on the complexity and fragility of BGP routing. To address these challenges, we present the DRIVER system for designing, analyzing and implementing policy-based routing protocols. Our system utilizes a declarative network verifier (DNV) which leverages declarative networking’s connection to logic programming by automatically compiling high-level declarativen networking program into formal specifications, which...

  7. A Logic Programming Language With Lambda-Abstraction, Function Variables, and Simple Unification

    Miller, Dale
    It has been argued elsewhere that a logic programming language with function variables and λ-abstractions within terms makes a good meta-programming language, especially when an object-language contains notions of bound variables and scope. The λProlog logic programming language and the related Elf and Isabelle systems provide meta-programs with both function .variables and λ-abstractions by containing implementations of higher-order unification. This paper presents a logic programming language, called Lλ, that also contains both function variables and λ-abstractions, although certain restrictions are placed on occurrences of function variables. As a result of these restrictions, an implementation of Lλ does not need to...

  8. Infinitary Logic and Inductive Definability Over Finite Structures

    Dawar, Anuj; Lindell, Steven; Weinstein, Scott
    The extensions of first-order logic with a least fixed point operators (FO + LFP) and with a partial fixed point operator (FO + PFP) are known to capture the complexity classes P and PSPACE respectively in the presence of an ordering relation over finite structures. Recently, Abiteboul and Vianu [AV91b] investigated the relation of these two logics in the absence of an ordering, using a mchine model of generic computation. In particular, they showed that the two languages have equivalent expressive power if and only if P = PSPACE. These languages can also be seen as fragments of an infinitary...

  9. Enriching a Meta-Language With Higher-Order Features

    Hannan, John; Miller, Dale
    Various meta-languages for the manipulation and specification of programs and programming languages have recently been proposed. We examine one such framework, called natural semantics, which was inspired by the work of G. Plotkin on operational semantics and extended by G. Kahn and others at INRIA. Natural semantics makes use of a first-order meta-language which represents programs as first-order tree structures and reasons about these using natural deduction-like methods. We present the following three enrichments of this meta-language. First, programs are represented not by first-order structures but by simply typed λ-terms. Second, schema variables in inference rules can be higher-order variables....

  10. Pi-Calculus: A Unifying Framework for Programming Paradigms

    Bangalore, Srinivas
    π-calculus is a calculus for modeling dynamically changing configurations of a network of communicating agents. This paper studies the suitability of π-calculus as a unifying framework to model the operational semantics of the three paradigms of programming: functional, logic and imperative paradigms. In doing so, the attempt is to demonstrate that π-calculus models a primitive that is pervasive in the three paradigms and to illustrate that the three forms of sequential computing are special instances of concurrent computing.

  11. Linear Time Logic Control of Discrete-Time Linear Systems

    Tabuada, Paulo; Pappas, George J
    The control of complex systems poses new challenges that fall beyond the traditional methods of control theory. One of these challenges is given by the need to control, coordinate and synchronize the operation of several interacting submodules within a system. The desired objectives are no longer captured by usual control specifications such as stabilization or output regulation. Instead, we consider specifications given by linear temporal logic (LTL) formulas. We show that existence of controllers for discrete-time controllable linear systems and LTL specifications can be decided and that such controllers can be effectively computed. The closed-loop system is of hybrid nature,...

  12. Robust Sampling for MITL Specifications

    Fainekos, Georgios E; Pappas, George J
    Real-time temporal logic reasoning about trajectories of physical systems necessitates models of time which are continuous. However, discrete time temporal logic reasoning is computationally more efficient than continuous time. Moreover, in a number of engineering applications only discrete time models are available for analysis. In this paper, we introduce a framework for testing MITL specifications on continuous time signals using only discrete time analysis. The motivating idea behind our approach is that if the dynamics of the signal fulfills certain conditions and the discrete time signal robustly satisfies the MITL specification, then the corresponding continuous time signal should also satisfy...

  13. Facsimile of LJS 56, Logica parva

    Porter, Dot

  14. Facsimile of LJS 457, Loyca parva ... etc.

    Porter, Dot

  15. Facsimile of LJS 229, Commentaries on Aristotle and Porphyry

    Porter, Dot

  16. Facsimile of LJS 203, Commentaries on the logical works of Aristotle

    Porter, Dot

  17. Facsimile of LJS 223, Questiones logicales ... etc.

    Porter, Dot

  18. Facsimile of LJS 224, Expositio in libros Posteriorum Aristotelis

    Porter, Dot

  19. Back To Events: More on the Logic of Verbal Modification

    Champollion, Lucas

  20. The Restorative Logic of Punishment: Another Argument in Favor of Weak Selection

    Baumard, Nicolas
    Strong reciprocity theorists claim that punishment has evolved to promote the good of the group and to deter cheating. By contrast, weak reciprocity suggests that punishment aims to restore justice (i.e., reciprocity) between the criminal and his victim. Experimental evidences as well as field observations suggest that humans punish criminals to restore fairness rather than to support group cooperation

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