http://www.cs.ox.ac.uk/seminars/ All en-gb 360 Thu, 23 Feb 2012 13:59:48 GMT Thu, 23 Feb 2012 01:59:48 GMT All http://blogs.law.harvard.edu/tech/rss/ http://www.cs.ox.ac.uk/seminars/710.html <br/>Room 105 Department of Computer Science, University of Oxford SeminarSeries All oucl-seminar-cakes-710 Wed, 25 Jan 2012 03:04:07 GMT http://www.cs.ox.ac.uk/seminars/687.html Department of Computer Science, University of Oxford SeminarSeries All oucl-seminar-oasis-687 Tue, 22 Nov 2011 11:27:16 GMT http://www.cs.ox.ac.uk/seminars/667.html <br/>380 Department of Computer Science, University of Oxford SeminarSeries All oucl-seminar-departmental-667 Fri, 07 Oct 2011 09:19:29 GMT http://www.cs.ox.ac.uk/seminars/718.html <br/>147 Department of Computer Science, University of Oxford SeminarSeries All oucl-seminar-infsys-718 Sun, 12 Feb 2012 06:29:09 GMT http://www.cs.ox.ac.uk/seminars/706.html <br/>Room 105 Department of Computer Science, University of Oxford SeminarSeries All oucl-seminar-cakes-706 Tue, 24 Jan 2012 01:55:46 GMT http://www.cs.ox.ac.uk/seminars/697.html <p>&nbsp;</p> <p>To be defined, but should deal with observations on the evolution of a large piece of code.</p> <br/>Room 051 Department of Computer Science, University of Oxford SeminarSeries All oucl-seminar-Software Engineering at Credit Suisse-697 Wed, 04 Jan 2012 24:20:12 GMT http://www.cs.ox.ac.uk/seminars/696.html <p>Quality assurance in very large information systems is a big challenge. We will talk about testing as a means to assure appropriate quality. Testing practices we will discuss include a multi-stage testing process, separate organizations for testing in order to be more efficient and avoid conflicts of interest, avoiding sensitive data in development and testing and static quality assurance. We will focus on how to test in a large, highly integrated application landscape. Finally, we will discuss testing practices that go beyond functional tests, such as performance, penetration, and destruction tests.</p> <br/>Room 051 Department of Computer Science, University of Oxford SeminarSeries All oucl-seminar-Software Engineering at Credit Suisse-696 Wed, 04 Jan 2012 24:20:12 GMT http://www.cs.ox.ac.uk/seminars/695.html <p>In this talk, we will make the point that the security of an information system is determined by the weakest link in a long chain of security measures, both technical and organizational. Very often this weakest link is human behavior, while it is very rarely a theoretical weakness in the cryptographic algorithm. We will show, how we focus on holistic design of security measures in order to strengthen the weakest link. Finally, we will discuss the necessary measures to secure financial transactions in the Internet and, becoming more important every day, on mobile devices.</p> <br/>Room 051 Department of Computer Science, University of Oxford SeminarSeries All oucl-seminar-Software Engineering at Credit Suisse-695 Wed, 04 Jan 2012 24:20:12 GMT http://www.cs.ox.ac.uk/seminars/694.html <p>Depending on the data they store and the processes they support, information systems incur different levels of risk. Credit Suisse categorizes its information systems in a finite number of levels along the three dimensions of availability/maximum data loss, confidentiality and integrity. Each level comes with clear guidelines regarding design, development and testing of the corresponding system. We will show the framework, explain some of the concepts in more detail and analyze how development and operating cost of a system changes when it has to fulfill different standards.</p> <br/>Room 051 Department of Computer Science, University of Oxford SeminarSeries All oucl-seminar-Software Engineering at Credit Suisse-694 Wed, 04 Jan 2012 24:17:34 GMT http://www.cs.ox.ac.uk/seminars/725.html Department of Computer Science, University of Oxford SeminarSeries All oucl-seminar-infsys-725 Thu, 23 Feb 2012 01:59:48 GMT http://www.cs.ox.ac.uk/seminars/724.html <p>I'll present a quick summary of the new reachability proof for Vector Addition Systems, designed by J. Leroux (POPL'11). Then, we'll consider a variation of Vector Addition Systems where one counter can be tested for zero and extend the proof of Leroux to our model. This provides an alternate, and hopefully simpler to understand, proof of the reachability problem that was originally proved by Reinhardt.<br /> <br />I'll end the talk by an overview of the various problems that are known decidable for Vector Addition Systems with one zero-test.<br /> <br />This is based on work published in MFCS'11.</p> <br/>380 Department of Computer Science, University of Oxford SeminarSeries All oucl-seminar-verification-724 Thu, 23 Feb 2012 09:07:28 GMT http://www.cs.ox.ac.uk/seminars/721.html <p>Programmable logic has been in the peripheral vision of computer science for the past 25 years or so. While the idea of &lsquo;soft hardware&rsquo; has seemed full of potential, productive application has been held back by two main factors: the small size of the physical devices, and the programming experience being akin to hardware chip design. The former issue has now been ameliorated by the emergence of modern FPGA devices containing millions of programmable logic gates, plus other embedded processing and memory. The latter issue is the subject of this talk. One line of attack is attempting to map general-purpose programming languages, with &ldquo;automatic extraction of parallelism&rdquo;. I prefer a domain-specific approach, looking to map natural domain parallelism onto the fine-grain concurrency of the FPGA. The talk will focus on the particular domain of packet processing. It has been shown that FPGAs have the raw capability to perform packet processing at very high data rates, currently up to 100-200 Gb/s, with 400 Gb/s and 1Tb/s on the horizon. The challenge is to allow the networking programmer in the street to describe packet processing problem instances, and automatically obtain FPGA solutions that deliver the required performance with acceptable power consumption. I will describe research on domain-specific languages for packet processing that has gone through several generations since 2005. Recent work demonstrated high-level packet parsing descriptions being compiled into 400 Gb/s rate FPGA implementations. The story of this research will not just cover the technicalities, but will also include discussion of what directions proved acceptable to the target audience, and what did not.</p> <br/>051 Department of Computer Science, University of Oxford SeminarSeries All oucl-seminar-verification-721 Mon, 20 Feb 2012 10:18:23 GMT http://www.cs.ox.ac.uk/seminars/717.html <p>Model checking based on Petri net unfoldings is an approach widely applied to cope with the state space explosion problem caused by concurrency. In this talk I will describe a recent condensed representation of a Petri net's behaviour called merged processes, which copes well not only with concurrency, but also with other sources of state space explosion, like sequences of choices and non-safeness. Moreover, this representation is sufficiently similar to the traditional unfoldings, so that a large body of results developed for the latter can be re-used. Experiments indicate that this representation of a Petri net's behaviour alleviates the state space explosion problem to a significant degree and is suitable for model checking.</p> Department of Computer Science, University of Oxford SeminarSeries All oucl-seminar-verification-717 Mon, 06 Feb 2012 11:00:02 GMT http://www.cs.ox.ac.uk/seminars/716.html <p>Stochastic modeling and algorithmic verification techniques have been proved useful in analyzing and detecting unusual trends in performance and energy usage of systems such as power management controllers and wireless sensor devices. Many important properties are dependent on the cumulated time that the device spends in certain states, possibly intermittently. We study the problem of verifying continuous-time Markov chains (CTMCs) against linear duration properties (LDP), i.e. properties stated as conjunctions of linear constraints over the total duration of time spent in states that satisfy a given property. We identify two classes of LDP properties, eventuality duration properties (EDP) and invariance duration properties (IDP), respectively referring to the reachability of a set of goal states, within a time bound; and the continuous satisfaction of a duration property over an execution path. The central question that we address is how to compute the probability of the set of infinite timed paths of the CTMC that satisfy a given LDP. We present algorithms to approximate these probabilities up to a given precision, stating their complexity and error bounds. The algorithms mainly employ an adaptation of uniformization and the computation of volumes of multi-dimensional integrals under systems of linear constraints, together with different mechanisms to bound the errors.<br /><br /> This is a rehearsal talk for HSCC12', joint work with Taolue Chen, Marta Kwiatkowska and Alexandru Mereacre.</p> <br/>147 Department of Computer Science, University of Oxford SeminarSeries All oucl-seminar-verification-716 Fri, 03 Feb 2012 09:54:14 GMT http://www.cs.ox.ac.uk/seminars/712.html <p>We present automatic verification techniques for the modelling and analysis of probabilistic systems that incorporate competitive behaviour. These systems are modelled as turn-based stochastic multi-player games, in which the players can either collaborate or compete in order to achieve a particular goal. We define a temporal logic called rPATL for expressing quantitative properties of stochastic multi-player games. This logic allows us to reason about the collective ability of a set of players to achieve a goal relating to the probability of an event's occurrence or the expected amount of cost/reward accumulated. We give a model checking algorithm for verifying properties expressed in this logic and implement the techniques in a probabilistic model checker, based on the PRISM tool. We demonstrate the applicability and efficiency of our methods by deploying them to analyse and detect potential weaknesses in a variety of large case studies, including algorithms for energy management and collective decision making for autonomous systems.<br /> <br />This is joint work with Taolue Chen, Vojtech Forejt, Marta Kwiatkowska and David Parker.</p> <br/>051 Department of Computer Science, University of Oxford SeminarSeries All oucl-seminar-verification-712 Thu, 26 Jan 2012 08:33:48 GMT http://www.cs.ox.ac.uk/seminars/723.html <p><span>In recent years, surprising connections between type theory and&nbsp;</span><span>homotopy theory have been discovered. In this talk I will recall the&nbsp;</span><span>notions of&nbsp;intensional type theories and identity types. I will&nbsp;</span><span>describe "infinity groupoids", formal algebraic models of topological&nbsp;</span><span>spaces, and explain how identity types carry the structure of an&nbsp;</span><span>infinity groupoid.&nbsp;I will finish by discussing categorical semantics&nbsp;</span><span>of intensional type theories.</span></p> <br/>Lecture Theatre B, Department of Computer Science Department of Computer Science, University of Oxford SeminarSeries All oucl-seminar-oasis-723 Wed, 22 Feb 2012 10:22:54 GMT http://www.cs.ox.ac.uk/seminars/709.html <br/>Lecture Theatre B (LTB) Department of Computer Science, University of Oxford SeminarSeries All oucl-seminar-oasis-709 Wed, 25 Jan 2012 24:31:53 GMT http://www.cs.ox.ac.uk/seminars/708.html <pre>By a fragment of a natural language we mean a subset of that language equipped with a semantics that translates its sentences into some formal system such as first-order logic. The familiar concepts of satisfiability and entailment can be defined for <br />any such fragment in a natural way. The question then arises, for any given fragment of a natural language, as to the computational complexity of determining satisfiability and entailment within that fragment. We present a series of fragments of <br />English whose satisfiability problems range in complexity from NLOGSPACE-complete to r.e.-complete, showing how different combinations of grammatical constructions conspire to yield the observed complexity. <br />We also discuss some proof-theoretical reflexes of these complexity results, in terms of the existence (or non-existence) of syllogism-like systems of inference rules for the fragments in question. Thus, this talk constitutes a study in how to <br />investigate the computational and logical properties of grammatical constructions in natural language.<br /></pre> <br/>Lecture Theatre B (LTB) Department of Computer Science, University of Oxford SeminarSeries All oucl-seminar-oasis-708 Wed, 25 Jan 2012 24:25:16 GMT http://www.cs.ox.ac.uk/seminars/722.html <p>One of the surprising developments in the area of program verification in the late part of the 20th Century is the emergence of Linear Temporal Logic (LTL), a logic that emerged in philisophical studies of free will, as the cannonical language for describing temporal behavior of computer systems. LTL, however, is not expressive enough for industrial applications. The first decade of the 21 Century saw the emergence of industrial temporal logics such as ForSpec, PSL, and SVA. These logics, however, are not clean enough to serve as objects of theoretical study. This talk will describe the rise and fall of LTL, and will propose a new cannonical temporal logic: Linear Dynamic Logic (LDL).</p> <br/>Lecture Theatre B Department of Computer Science, University of Oxford SeminarSeries All oucl-seminar-departmental-722 Mon, 20 Feb 2012 08:34:39 GMT http://www.cs.ox.ac.uk/seminars/719.html <p>Despite significant advances in programming languages and verification tools, programming <br />remains a tedious, error-prone, and expensive activity.&nbsp; This talk surveys an emerging approach <br />to software design in&nbsp; which a programmer and an automated program-synthesis tool collaborate <br />to generate software that meets its specification.&nbsp; A programmer expresses her insights about the <br />design using synthesis artifacts of different kinds such as programs that may contain ambiguities, <br />declarative specifications of high-level requirements,&nbsp; positive and negative examples of desired <br />behaviors, and optimization criteria for selecting among alternative implementations. <br />The synthesis tool composes these different views about the structure and functionality of the system <br />into a unified&nbsp; concrete implementation using a combination of algorithmic techniques such as decision <br />procedures for constraint-satisfaction problems, iterative schemes for abstraction and refinement, <br />and data-driven learning. We will illustrate this approach using a number of projects, including one <br />at Penn focusing on design of cache coherence protocols from a mix of concrete and symbolic <br />execution scenarios.</p> <br/>Lecture Theatre B Department of Computer Science, University of Oxford SeminarSeries All oucl-seminar-strachey-719 Mon, 13 Feb 2012 10:33:38 GMT