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ABSTRACT: Web services choreography is used to design peer-to-peer applications where each peer is potentially a Web service. It defines the required behavior of participating Web services along with their interactions through message exchanges. Implementing a complex system described by a choreography requires selecting actual Web services whose individual behaviors are compatible with the overall behavior described by the choreography. Although the selected Web services implement the specified behavior, they may not be able to interact due to the policies they enforce to protect their resources. A Web service' resource can be an operation or a credential type to be submitted to be able to invoke an operation. In this paper, we propose a novel approach to determine at design time whether a choreography can be implemented by a set of Web services based on their access control policies and the disclosure policies regulating the release of their credentials. We model both Web services and Web services choreography as transition systems and represent Web services credential disclosure policies as directed graphs. We then verify that all possible conversations of the Web services choreography can be implemented by matching credential disclosure policies of the invoker Web service with the access control policy of the Web services being invoked. We propose a resource release graph to enable this verification.
Services Computing, 2008. SCC '08. IEEE International Conference on; 08/2008
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ABSTRACT: Existing techniques for schema matching are classified as either schema-based, instance-based, or a combination of both. In this paper, we define a new class of techniques, called usage-based schema matching. The idea is to exploit information extracted from the query logs to find correspondences between attributes in the schemas to be matched. We propose methods to identify co-occurrence patterns between attributes in addition to other features such as their use in joins and with aggregate functions. Several scoring functions are considered to measure the similarity of the extracted features, and a genetic algorithm is employed to find the highest- score mappings between the two schemas. Our technique is suitable for matching schemas even when their attribute names are opaque. It can further be combined with existing techniques to obtain more accurate results. Our experimental study demonstrates the effectiveness of the proposed approach and the benefit of combining it with other existing approaches.
Data Engineering, 2008. ICDE 2008. IEEE 24th International Conference on; 05/2008
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ABSTRACT: Annotations and provenance data play a key role in under-standing and curating scientific databases. However, cur-rent database management systems lack adequate support for managing annotations and provenance data including: (1) handling annotations at multiple granularities, i.e., at the table, tuple, column and cell levels, (2) propagating an-notations along with query answers, (3) querying data based on their annotations, and (4) providing declarative ways to add, archive, and restore annotations. In this paper, we propose to treat multi-granular annotations and provenance as first class objects inside the database. We introduce the concept of "Annotated Relations" along with new operators and extended semantics for the standard relational oDera-tors in support of annotated relations. We present an ex-pressive and declarative extension to SQL to support the processing and querying of annotated tables. We study sev-eral schemes for storing and indexing annotations based on annotation granularity and annotation size. Extensions to PostgreSQL are introduced to support annotated relations and implementation challenges are discussed. Performance analysis illustrates the potential of annotated relations as they achieve up to an order-of-magnitude reduction in stor-age and I/O costs.
12/2007;
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ABSTRACT: Space-partitioning trees, like the disk-based trie, quadtree, kd-tree and their variants, are a family of access methods that index multi-dimensional objects. In the case of indexing non-zero extent objects, e.g., line segments and rectangles, space-partitioning trees may replicate objects over multiple space partitions, e.g., PMR quadtree, expanded MX-CIF quadtree, and extended kd-tree. As a result, the answer to a query over these indexes may include duplicates that need to be eliminated, i.e., the same object may be reported more than once. In this paper, we propose generic duplicate elimination techniques for the class of space-partitioning trees in the context of SP-GiST; an extensible indexing framework for realizing space-partitioning trees. The proposed techniques are embedded inside the INDEX-SCAN operator. Therefore, duplicate copies of the same object do not propagate in the query plan, and the elimination process is transparent to the end-users. Two cases for the index structures are considered based on whether or not the objects' coordinates are stored inside the index tree. The theoretical and experimental analysis illustrate that the proposed techniques achieve savings in the storage requirements, I/O operations, and processing time when compared to adding a separate duplicate elimination operator in the query plan.
Scientific and Statistical Database Management, 2007. SSBDM '07. 19th International Conference on; 08/2007
