| URL | http://www-db.stanford.edu/pub/papers/wrapper-demo.ps |
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| Title | Template-Based Wrappers in the TSIMMIS System. |
| Authors | J. Hammer , M. Breunig , H. Garcia-Molina , S. Nestorov , V. Vassalos , R. Yerneni |
| Year | 1997 |
| Citation | In Proceedings of the Twenty-Sixth SIGMOD International Conference on Management of Data, Tucson, Arizona, May 12-15, 1997. |
| Keywords | |
| Abstract | T emplate-Based W rappers in the tsimmis System Joachim Hammer, Hector Garcia-Molina, Svetlozar Nestorov, Ramana Yerneni, Marcus Breunig, Vasilis Vassalos Department of Computer Science Stanford University Stanford, CA 94305-9040 E-mail: fjoachim,hector,evtimov,yerneni,vassalosg@db.stanford.edu http://www-db.stanford.edu/tsimmis 1 Overview In order to access information from a variety of heterogeneous information sources, one has to be able to translate queries and data from one data model into another. This functionality is provided by so-called (source) wrappers [4,8] which convert queries into one or more commands/queries understandable by the underlying source and transform the native results into a format understood by the application. As part of the tsimmis project [1, 6] we have developed hard-coded wrappers for a variety of sources (e.g., Sybase DBMS, WWW pages, etc.) including legacy systems (FHowever, anyone who has built a wrapper before can attest that a lot of effort goe |
| URL | http://www-db.stanford.edu/pub/papers/cap.ps |
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| Title | Capability Based Mediation in TSIMMIS |
| Authors | C. Li , R. Yerneni , V. Vassalos , H. Garcia-Molina , Y. Papakonstantinou , J. Ullman , M. Valiveti |
| Year | 1998 |
| Citation | Demonstration description in proceedings of SIGMOD 98 |
| Keywords | information integration, heterogeneous databases, mediator, plan generation |
| Abstract | Conventional mediators focus their attention on the contents of the sources and their relationship to the integrated views provided to the users. They do not take into account the capabilities of sources to answer queries. This may lead them to generate plans involving source queries that cannot be answered by the sources. In the TSIMMIS system, we have developed a source capability sensitive plan generation module that constructs feasible plans for user queries in the presence of limited source capabilities. |
| URL | http://www-db.stanford.edu/pub/papers/expr-cap.ps |
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| Title | Expressive Capabilities Description Languages and Query Rewriting Algorithms |
| Authors | V. Vassalos , Y. Papakonstantinou |
| Year | 1998 |
| Citation | Accepted for publication in the Journal of Logic Programming, Special issue on Logic-Based Heterogeneous Information Systems |
| Keywords | information integration, mediators, heterogeneous databases, capability-based rewriting, query languages, expressibility |
| Abstract | Information integration systems have to cope with a wide variety of different information sources, which support query interfaces with very varied capabilities. To deal with this problem, the integration systems need descriptions of the query capabilities of each source, i.e., the set of queries supported by each source. Moreover, the integration systems need algorithms for deciding how a query can be answered given the capabilities of the sources. Finally, they need to translate a query into the format that the source understands. We present two languages suitable for descriptions of query capabilities of sources and compare their expressive power. We also use one of the languages to automatically derive the capabilities description of the integration system itself, in terms of the capabilities of the sources it integrates. We describe algorithms for deciding whether a query "matches" the description and show their application to the problem of translating user queries into source-sp |
| URL | http://www-db.stanford.edu/pub/papers/mslcont.ps |
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| Title | Query rewriting using semistructured views |
| Authors | Y. Papakonstantinou , V. Vassalos |
| Year | 1998 |
| Citation | Technical Report |
| Keywords | information integration, semistructured data, heterogeneneous databases, query rewriting,views |
| Abstract | We address the problem of query rewriting for TSL, a language for querying semistructured data. We develop and present an algorithm that, given a semistructured query q and a set of semistructured views V, finds rewriting queries, i.e., queries that access the views and produce the same result as q. Our algorithm is based on appropriately generalizing containment mappings, the chase, and unification -- techniques that were developed for structured, relational data. We also develop an algorithm for equivalence checking of TSL queries. We show that the algorithm is sound and complete for TSL, i.e., it always finds every TSL rewriting query of q, and we discuss its complexity. We extend the rewriting algorithm to use available structural constraints (such as DTDs) to find more opportunities for query rewriting. We currently incorporate the algorithm in the TSIMMIS system. |
| URL | http://www-db.stanford.edu/pub/papers/integr-optim.ps |
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| Title | Using Knowledge of Redundancy for Query Optimization in Mediators |
| Authors | V. Vassalos , Y. Papakonstantinou |
| Year | 1998 |
| Citation | Proceedings of the AAAI Workshop on AI and Information Integration, Madison, Wisconsin, July 1998. |
| Keywords | information integration, heterogeneous databases, mediators, redundancy, source overlap, WWW |
| Abstract | ABSTRACT: Many autonomous and heterogeneous information sources are becoming increasingly available to the user through the Internet -- especially through the World Wide Web. The integration of Internet sources poses several challenges which have not been sufficiently addressed. In particular, knowledge of redundancy can be used to reduce the number of source accesses that have to be performed to retrieve the answer to the user query. Moreover, probabilistic information about source overlap can help derive efficient query plans for delivering partial answers to queries. |
| URL | http://www-db.stanford.edu/pub/papers/incr-oemviews.ps |
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| Title | Incremental Maintenance for Materialized Views over Semistructured Data |
| Authors | S. Abiteboul , J. McHugh , M. Rys , V. Vassalos , J. Wiener |
| Year | 1998 |
| Citation | VLDB 98 |
| Keywords | semistructured data, incremental view maintenance |
| Abstract | Semistructured data is not strictly typed like relational or object-oriented data and may be irregular or incomplete. It often arises in practice, e.g., when heterogeneous data sources are integrated or data is taken from the World Wide Web. Views over semistructured data can be used to filter the data and to restructure (or provide structure to) it. To achieve fast query response time, these views are often materialized. This paper studies incremental maintenance techniques for materialized views over semistructured data. We use the graph-based data model OEM and the query language Lorel, developed at Stanford, as the framework for our work. We propose a new algorithm that produces a set of queries that compute the changes to the view based upon a change to the source. We develop an analytic cost model and compare the cost of executing our incremental maintenance algorithm to that of recomputing the view. We show that for nearly all types of database updates, it is more efficie |
| URL | http://www-db.stanford.edu/pub/papers/tsimmis.ps |
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| Title | The TSIMMIS approach to mediation: Data models and Languages |
| Authors | H. Garcia-Molina , Y. Papakonstantinou , D. Quass , A. Rajaraman , Y. Sagiv , J. Ullman , V. Vassalos , J. Widom |
| Year | 1997 |
| Citation | In Journal of Intelligent Information Systems - journal version of http://www-db.stanford.edu/pub/papers/tsimmis-models-languages.ps |
| Keywords | Heterogeneous Databases, Information Integration, Semistructured Data |
| Abstract | TSIMMIS -- The Stanford-IBM Manager of Multiple Information Sources -- is a system for integrating information. It offers a data model and a common query language that are designed to support the combining of information from many different sources. It also offers tools for generating automatically the components that are needed to build systems for integrating information. In this paper we shall discuss the principal architectural features and their rationale. |
| URL | http://www-db.stanford.edu/pub/papers/query-cap.ps |
|---|---|
| Title | Describing and Using Query Capabilities of Heterogeneous Sources |
| Authors | V. Vassalos , Y. Papakonstantinou |
| Year | 1997 |
| Citation | VLDB'97 |
| Keywords | Information Integration, Heterogeneous Databases, Mediators |
| Abstract | Information integration systems have to cope with the different and limited query interfaces of the underlying information sources. First, the integration systems need descriptions of the query capabilities of each source, i.e., the set of queries supported by each source. Second, the integration systems need algorithms for deciding how a query can be answered given the capabilities of the sources. Third, they need to translate a query into the format that the source understands. We present two languages suitable for descriptions of query capabilities of sources and compare their expressive power. We also describe algorithms for deciding whether a query "matches" the description and show their application to the problem of translating user queries into source-specific queries and commands. Finally, we propose new improved algorithms for the problem of answering queries using these descriptions. |
| URL | http://www-db.stanford.edu/pub/papers/oemview97.ps |
|---|---|
| Title | Views for Semistructured Data |
| Authors | S. Abiteboul , R. Goldman , J. McHugh , V. Vassalos , Y. Zhuge |
| Year | 1997 |
| Citation | 1997 Workshop on Management of Semistructured Data |
| Keywords | Semistructured Databases, Heterogeneous Databases, Views |
| Abstract | Defining a view over a semistructured database introduces many new problems. In this paper we propose a view specification language and consider the problem of answering queries posed over views. The two main approaches, query rewriting and view materialization, are outlined with focus on the diffcult problems caused by the semistructured nature of the data. |
| URL | http://www-db.stanford.edu/pub/papers/techtransfer.ps |
|---|---|
| Title | An Analysis of Factors Directing the Admission Process of Artificial Intelligence Technologies |
| Authors | V. Vassalos , S. Venkatasubramanian |
| Year | 1995 |
| Citation | 8th International Symposium on Artificial Intelligence, Monterrey, Mexico, Oct 1995. |
| Keywords | AI, industry, technology transfer |
| Abstract |
[Stanford University | Computer Science Dept | Database Group]
Qingshan Luo
/ qluo@cs.stanford.edu / Last updated on 9/30/96.