952247
Understanding Web query interfaces: best-effort parsing with hidden syntax
Recently, the Web has been rapidly "deepened" by many searchable databases online, where data are hidden behind query forms. For modelling and integrating Web databases, the very first challenge is to understand what a query interface says- or what query capabilities a source supports. Such automatic extraction of interface semantics is challenging, as query forms are created autonomously. Our approach builds on the observation that, across myriad sources, query forms seem to reveal some "concerted structure," by sharing common building blocks. Toward this insight, we hypothesize the existence of a hidden syntax that guides the creation of query interfaces, albeit from different sources. This hypothesis effectively transforms query interfaces into a visual language with a non-prescribed grammar- and, thus, their semantic understanding a parsing problem. Such a paradigm enables principled solutions for both declaratively representing common patterns, by a derived grammar, and systematically interpreting query forms, by a global parsing mechanism. To realize this paradigm, we must address the challenges of a hypothetical syntax- that it is to be derived, and that it is secondary to the input. At the heart of our form extractor, we thus develop a 2P grammar and a best-effort parser, which together realize a parsing mechanism for a hypothetical syntax. Our experiments show the promise of this approach-it achieves above 85% accuracy for extracting query conditions across random sources.
32378250
Using Distributed Objects to Build the Stanford Digital Library Infobus
For digital libraries to thrive, the providers of information processing services must be able to evolve their systems autonomously. However, as the complexity of their offerings increases, software tools more sophisticated than existing Web facilities are needed. Distributed object technology may be the answer. The availability of high-volume, increasingly sophisticated information is making the need for metadata facilities more urgent. Traditional, library-based approaches break down when used in an advanced digital library. More modular mechanisms are needed, and the CORBA system is one approach. Digital libraries are affected at a deep technical level by the widely differing user traditions of Web users and library patrons. The challenge and opportunity of digital libraries will be the synthesis of these traditions. The authors set out to create a technical infrastructure to support the construction of digital libraries. In their view, a digital library comprises widely distributed resources that can be maintained autonomously by different organizations and will not require adherence to uniform interfaces.
6980873
Making holistic schema matching robust: an ensemble approach
The Web has been rapidly "deepened" by myriad searchable databases online, where data are hidden behind query interfaces. As an essential task toward integrating these massive "deep Web" sources, large scale schema matching (i.e., discovering semantic correspondences of attributes across many query interfaces) has been actively studied recently. In particular, many works have emerged to address this problem by "holistically" matching many schemas at the same time and thus pursuing "mining" approaches in nature. However, while holistic schema matching has built its promise upon the large quantity of input schemas, it also suffers the robustness problem caused by noisy data quality. Such noises often inevitably arise in the automatic extraction of schema data, which is mandatory in large scale integration. For holistic matching to be viable, it is thus essential to make it robust against noisy schemas. To tackle this challenge, we propose a data-ensemble framework with sampling and voting techniques, which is inspired by bagging predictors. Specifically, our approach creates an ensemble of matchers, by randomizing input schema data into many independently downsampled trials, executing the same matcher on each trial and then aggregating their ranked results by taking majority voting. As a principled basis, we provide analytic justification of the effectiveness of this data-ensemble framework. Further, empirically, our experiments on real Web data show that the "ensemblization" indeed significantly boosts the matching accuracy under noisy schema input, and thus maintains the desired robustness of a holistic matcher.
2091518
Evaluating the cost of Boolean query mapping
Non-uniform query languages make searching over heterogeneous information sources difcult. Our approach is to allow a user to compose Boolean queries in one rich front-end language. For each user query and target source, we transform the user query into a subsuming query that can be supported by the source but that may return extra documents. The results are then processed by a lter query to yield the correct nal results. This post-ltering approach may involve signicant cost because the documents that the users will not see may have to be retrieved and ltered. There are generally two ways to implement post-ltering: batch post-ltering and incremental post-ltering. In this paper we evaluate the costs of both methods for different search features such as proximity operators. The experimental results show that in many cases incremental post-ltering cost may be acceptable, while the batch post-ltering cost may sometimes be extremely large.
5658776
Metadata for digital libraries: architecture and design rationale
In a distributed, heterogeneous, proxy-based digital library, autonomous services and collections are accessed indirectly via proxies. To facilitate metadata compatibility and interoperability in such a digital library, we have designed a metadata architecture that includes four basic component classes: attribute model proxies, attribute model translators, metadata facilities for search proxies, and metadata repositories. Attribute model proxies elevate both attribute sets and the attributes they define to first-class objects. They also allow relationships among attributes to be captured. Attribute model translators map attributes and attribute values from one attribute model to another (where posMetadata facilities for search proxies provide structured descriptions both of the collections to which the search proxies provide access and of the search capabilities of the proxies. Finally, metadata repositories accumulate selected metadata from local instances of the other three component classes in order to facilitate global metadata queries and local metadata caching. In this paper, we outline further the roles of these component classes, discuss our design rationale, and analyze related work. Keywords: Metadata architecture, interoperability, attribute model, attribute model translation, metadata repository, InfoBus, proxy architecture, heterogeneity, digital libraries, CORBA.
15321340
Approximate Query Translation Across Heterogeneous Information Sources
In this paper we present a mechanism for approximately translating Boolean query constraints across heterogeneous information sources. Achieving the best translation is challenging because sources support different constraints for formulating queries, and often these constraints cannot be precisely translated. For instance, a query [score > 8] might be “perfectly” translated as [rating > 0.8] at some site, but can only be approximated as [grade = A] at another. Unlike other work, our general framework adopts a customizable “closeness” metric for the translation that combines both precision and recall. Our results show that for query translation we need to handle interdependencies among both query conjuncts as well as disjuncts. As the basis, we identify the essential requirements of a rule system for users to encode the mappings for atomic semantic units. Our algorithm then translates complex queries by rewriting them in terms of the semantic units. We show that, under practical assumptions, our algorithm generates the best approximate translations with respect to the closeness metric of choice. We also present a case study to show how our technique may be applied in practice.
13199279
Rule-mitigated collaboration framework
Computer supported cooperative work (CSCW) research is the discipline that explores how to utilize computing and networking technologies to facilitate cooperation and collaboration among people. A variety of research has been conducted on CSCW architecture. However, how to ensure CSCW system effectiveness and efficiency on supporting collaboration remains a challenge. In this paper we present a rule mitigated framework for CSCW applications. This research contributes to the state of the art by presenting a robust and comprehensive architecture to support distributed collaboration.
7105622
The space complexity of pass-efficient algorithms for clustering
We present multiple pass streaming algorithms for a basic clustering problem for massive data sets. If our algorithm is allotted 2l passes, it will produce an approximation with error at most ε using Õ(k3/ε2/l) bits of memory, the most critical resource for streaming computation. We demonstrate that this tradeoff between passes and memory allotted is intrinsic to the problem and model of computation by proving lower bounds on the memory requirements of any l pass randomized algorithm that are nearly matched by our upper bounds. To the best of our knowledge, this is the first time nearly matching bounds have been proved for such an exponential tradeoff for randomized computation.In this problem, we are given a set of n points drawn randomly according to a mixture of k uniform distributions and wish to approximate the density function of the mixture. The points are placed in a datastream (possibly in adversarial order), which may only be read sequentially by the algorithm. We argue that this models, among others, the datastream produced by a national census of the incomes of all citizens.
17374517
Model Checking with Induction
We have proposed inductive model checking (IMC) to alleviate the state explosion problem in model checking. IMC divides the whole verification tasks into several sub-tasks, and applies the three inductive steps (basis, hypothesis, and induction) to verify a system with model checking. In this paper, we continue our research by determining those temporal formulas, namely, persistent temporal formulas, which are verifiable with IMC. One important characteristic of a persistent temporal formula is that it contains a periodic temporal formula that must be held persistently. From the verification results of the periodic formula with different sequences of states, IMC concludes the verification of the persistent temporal formula
15818010
Automatic Partitioner for Behavior Level Distributed Logic Simulation
As the complexity of circuit design increases, verification through simulation has become a bottleneck of the IC design process. Distributed parallel simulation is one way to solving the problem. In order to distribute the simulation workload to multiple processors, the design must be carefully partitioned first. While most previous work focus on gate level partitioning, our work extends a previously implemented Verilog gate-level partitioner to support RTL and behavior level partitioning. Techniques to partition special constructs specific to these levels, such as global access, function calls and memory access, are described in this paper. The experimental results show that our techniques are capable of finding partitions which can accelerate simulation.
2264058
A Unified Model for Probabilistic Principal Surfaces
Principal curves and surfaces are nonlinear generalizations of principal components and subspaces, respectively. They can provide insightful summary of high-dimensional data not typically attainable by classical linear methods. Solutions to several problems, such as proof of existence and convergence, faced by the original principal curve formulation have been proposed in the past few years. Nevertheless, these solutions are not generally extensible to principal surfaces, the mere computation of which presents a formidable obstacle. Consequently, relatively few studies of principal surfaces are available. We previously (2000) proposed the probabilistic principal surface (PPS) to address a number of issues associated with current principal surface algorithms. PPS uses a manifold oriented covariance noise model, based on the generative topographical mapping (GTM), which can be viewed as a parametric formulation of Kohonen's self-organizing map. Building on the PPS, we introduce a unified covariance model that implements PPS (0 1) by varying the clamping parameter /spl alpha/. Then, we comprehensively evaluate the empirical performance of PPS, GTM, and the manifold-aligned GTM on three popular benchmark data sets. It is shown in two different comparisons that the PPS outperforms the GTM under identical parameter settings. Convergence of the PPS is found to be identical to that of the GTM and the computational overhead incurred by the PPS decreases to 40 percent or less for more complex manifolds. These results show that the generalized PPS provides a flexible and effective way of obtaining principal surfaces.