Most databases contain "name constants" like course numbers, personal names, and place names that correspond to entities in the real world. Previous work in integration of heterogeneous databases has assumed that local name constants can be mapped into an appropriate global domain by normalization. However, in many cases, this assumption does not hold; determining if two name constants should be considered identical can require detailed knowledge of the world, the purpose of the user's query, or both. In this paper, we reject the assumption that global domains can be easily constructed, and assume instead that the names are given in natural language text. We then propose a logic called WHIRL which reasons explicitly about the similarity of local names, as measured using the vector-space model commonly adopted in statistical information retrieval. We describe an efficient implementation of WHIRL and evaluate it experimentally on data extracted from the World Wide Web. We show that WHIR...

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Abstract. Separation logic is a program logic for reasoning about programs that manipulate pointer data structures. We describe Smallfoot, a tool for checking certain lightweight separation logic specifications. The assertions describe the shapes of data structures rather than their detailed contents, and this allows reasoning to be fully automatic. The presentation in the paper is tutorial in style. We illustrate what the tool can do via examples which are oriented toward novel aspects of separation logic, namely: avoidance of frame axioms (which say what a procedure does not change); embracement of “dirty ” features such as memory disposal and address arithmetic; information hiding in the presence of pointers; and modular reasoning about concurrent programs. 1

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We measure and analyze the single-hop packet delay through operational routers in a backbone IP network. First we present our delay measurements through a single router. Then we identify stepby -step the factors contributing to single-hop delay. In addition to packet processing, transmission, and queueing delays, we identify the presence of very large delays due to non-work-conserving router behavior. We use a simple output queue model to separate those delay components. Our step-by-step methodology used to obtain the pure queueing delay is easily applicable to any single-hop delay measurements.

We present new BSP algorithms for deterministic sorting and randomized median finding. We sort n general keys by using a partitioning scheme that achieves the requirements of efficiency (one-optimality) and insensitivity against data skew (the accuracy of the splitting keys depends solely on the step distance, which can be adapted to meet the worstcase requirements of our application). Although we employ sampling in order to realize efficiency, we can give a precise worst-case estimation of the maximum imbalance which might occur. We also investigate optimal randomized BSP algorithms for the problem of finding the median of n elements that require, with high-probability, 3n=(2p) + o(n=p) number of comparisons, for a wide range of values of n and p. Experimental results for the two algorithms are also presented.

this paper is to present, in a completely algorithmic form, a description of five basic calendars and how they relate to one another: the present civil calendar (Gregorian), the recent ISO commercial calendar, the old civil calendar (Julian), the Islamic (Moslem) calendar, and the Hebrew (Jewish) calendar. Information that is sufficiently detailed to allow computer implementation is difficult to find for the Islamic and Hebrew calendars since the published material is often inaccessible, ecclesiastically oriented, incomplete, inaccurate, based on extensive tables, overburdened with extraneous material, focused on shortcuts for hand calculation to 0038--0644/90/090899--30$15.00 Received 31 August 1989 c fl 1990 by John Wiley & Sons, Ltd. Revised 27 March 1990 avoid complicated arithmetic or to check results, or difficult to find in English. Most existing computer programs are proprietary, incomplete, or inaccurate

Most general-purpose processors provide support for memory pages of large sizes, called superpages. Superpages enable each entry in the translation lookaside buffer (TLB) to map a large physical memory region into a virtual address space. This dramatically increases TLB coverage, reduces TLB misses, and promises performance improvements for many applications. However, supporting superpages poses several challenges to the operating system, in terms of superpage allocation and promotion tradeoffs, fragmentation control, etc. We analyze these issues, and propose the design of an effective superpage management system. We implement it in FreeBSD on the Alpha CPU, and evaluate it on real workloads and benchmarks. We obtain substantial performance benefits, often exceeding 30%; these benefits are sustained even under stressful workload scenarios. 1

In this work, control strategies for combining two potentially powerful buffer management techniques in object bases were devised and evaluated: (1) buffer pool segmentation with segment-specific replacement criteria, and (2) dual buffering consisting of copying objects from pages into object buffers. Two diien-sions exist for exerting control on the buffer pool: (1) the copying time which determines at what time objects are copied from their memory-resident home page, and (2) the relo-cation time which determines when a (copied) object is to be transferred back to its home page. Along both dimensions, it is possible to differentiate between an eager and a lazy strategy. The extensive experimental results indicate that lazy object copying combined with an eager relocation strategy is almost always superior and significantly outperforms page-based buffering in most applications. 1

Abstract. Previous shape analysis algorithms use a memory model where the heap is composed of discrete nodes that can be accessed only via access paths built from variables and field names, an assumption that is violated by pointer arithmetic. In this paper we show how this assumption can be removed, and pointer arithmetic embraced, by using an analysis based on separation logic. We describe an abstract domain whose elements are certain separation logic formulae, and an abstraction mechanism that automatically transits between a low-level RAM view of memory and a higher, fictional, view that abstracts from the representation of nodes and multiword linked-lists as certain configurations of the RAM. A widening operator is used to accelerate the analysis. We report experimental results obtained from running our analysis on a number of classic algorithms for dynamic memory management. 1