H. Garcia-Molina, Y. Papakonstantinou, D. Quass, A. Rajararnan, Y. Sagiv, J. Ullman, V. Vassalos, and J. Widom, "The TSIMMIS Approach to Mediation: Data Models and Languages", Journal of Intelligent Information Systems, 2 (1997) 117132.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....author in locating data sources. Unfortunately, applications must still be familiar with a common domain language and they must be somewhat familiar with the underlying database schemas to formulate queries. Systems using the fourth approach communicate via explicit schema mappings. Tsimmis [13] integrates heterogeneous information systems by placing translators (or wrappers) around all information servers. Translators are written to convert the domain specific database representations to a common model. Domain applications call mediators, which are at a level above the translators, to ....

H. Garcia-Molina, Y. Papakonstantinou, D. Quass, A. Rajararnan, Y. Sagiv, J. Ullman, V. Vassalos, and J. Widom, "The TSIMMIS Approach to Mediation: Data Models and Languages", Journal of Intelligent Information Systems, 2 (1997) 117132.

....semantic relations are defined as views. Different mediators are needed to answer different queries or to build distinct relations among data. Existing systems in this class provide the programmer who has designed the mediator, tools to integrate domains, information and to handle conflicts [14, 17 and 18] Mediator Mediator Wrapper Wrapper Source Source Figure 1. A network of Mediators, Wrappers and Information Sources [19] In the latter approach to the design of mediator based systems, query formulation is an activity that stems out from the definition of an integrated schema ....

H. Garcia-Molina, Y. Papakonstantinou, D. Quass, A. Rajaraman, Y. Sagiv, J. Ullman, V. Vassalos, J. Widom, "The TSIMMIS Approach to Mediation: Data Models and Languages", in Journal of Intelligent Information Systems, 1997.

....the semantic relations are defined as views. Different mediators are needed to answer different queries or to build distinct relations among data. Existing systems in this class provide the programmer who has designed the mediator, tools to integrate domains, information and to handle conflicts. Gar97, Lev96 and Sub98) In the latter approach to the of design mediator based systems, query formulation is an activity that stems out from the definition of an integrated schema requiring a partial or total unification of the local data models (Are93, Har97 and She88) In spite of the greatest ....

H. Garcia-Molina, Y. Papakonstantinou, D. Quass, A. Rajaraman, Y. Sagiv, J. Ullman, V. Vassalos, J. Widom, The TSIMMIS Approach to Mediation: Data Models and Languages", in Journal of Intelligent Information Systems, 1997. Available @ http://www-db.stanford.edu/pub/papers/tsimmis.ps.

.... view over virtual classes of the mediator [11, 3] This mediation approach is called local as view (LAV) that is in contrast to global as view (GAV) 4] where information sources should be pre selected before a mediator formation and a global mediator s schema should be defined for them [5, 16]. LAV approach is intended to cope with a dynamic, possibly incomplete set of sources. Sources may change their exported schemas, become unavailable from time to time. Registration method for the LAV approach treated as the process of compositional information systems development is introduced in ....

H. Garcia-Molina, J. Hammer, K. Ireland, Y. Papakonstantinou, J. Ullman, and J. Widom. The Tsimmis Approach to Mediation: Data Models and Languages. Journal of Intelligent Information System, 1997

....the traditional strategy developed for federated databases [12] The global view is constructed by several layers of views on the relations exported by the sources. Queries are expressed in terms of the global view and are evaluated in the conventional way. GAV is the strategy applied by TSIMMIS [7], HERMES [13] and Gestalt [11] for instance. The (LAV) considers that the relations exported by the sources are materialized views defined on virtual relations in the global schema. Queries are still expressed in terms of the global schema. In order to evaluate a query, a rewriting in terms of ....

H. Garcia-Molina, J. Hammer, K. Ireland, Y. Papakonstantinou, J. Ullman, and J. Widom. The TSIMMIS Approach to Mediation: Data Models and Languages. Journal of Intelligent Information System, 1997.

....This scheme has to be powerful enough to combine all characteristics of a collection and simple enough to enhance its acceptance. Improving access to heterogenous information sources is an active area of research. Academic systems using the mediator approach are Ariadne [2] Tsimmis [5] and Information Manifold [12] Popular examples of commercial meta search engines are MetaCrawler 5 and Highway61 6 . In the next three sections we address these issues, offering practical solutions for each. In Section 5 we prove their feasibility by introducing an architecture of a meta ....

H. Garcia-Molina, Y. Papakonstantinou, D. Quass, A. Rajaraman, Y. Sagiv, J. Ullman, and J. Widom. The tsimmis approach to mediation: Data models and languages. In Proceedings of Second International Workshop on Next Generation Information Technologies and Systems, 1995.

....meaning is speci ed in terms of the data residing at the sources. In general, the views associated to the elements of the global schema are considered sound, i.e. they provide a subset of the data satisfying the global schema, rather than the complete set. Examples of global centric systems are [15, 2, 16]. The second approach, called source centric, requires the global schema to be speci ed independently from the sources. In turn, the sources are de ned as views over the global schema. Examples of source centric systems are [21, 11, 6] Comparisons of the two approaches are reported in [31, 5] In ....

Hector Garcia-Molina, Yannis Papakonstantinou, Dallan Quass, Anand Rajaraman, Yehoshua Sagiv, Jerey D. Ullman, Vasilis Vassalos, and Jennifer Widom. The TSIMMIS approach to mediation: Data models and languages. J. of Intelligent Information Systems, 8(2):117-132, 1997. 17

....for integrated and unified access to multiple information sources has stimulated the research on mediators. The concept of mediator was initially proposed by Wiederhold [23] Since then many different approaches have been proposed in order to build mediators over relational databases (e.g. see [13, 7, 8, 24]) SGML documents (e.g. see [5] or information retrieval systems (e.g. see [22, 9, 6, 19, 16] and web based sources (e.g. see [1, 3] Comparing to the integration approaches for relational databases, namely, federated databases, relational warehousing, and relational mediation, our model is ....

....a single mode of operation while our mediators are flexible as they allow multiple modes of operation. The techniques for building relational mediators are appropriate for rendering the structural (schema) heterogeneities of the sources transparent to the users (see the systems TSIMMIS [4] [7], HERMES [18] Information Manifold [13] However these approaches do not support approximate translation although there are many scenarios in which this functionality is necessary. One approach that considers approximate translations is [3] The queries considered there are boolean expressions ....

H. Garcia-Molina, Y. Papakonstantinou, D. Quass, A. Rajaraman, Y. Sagiv, J. Ullman, V. Vassalos, and J. Widom. "The TSIMMIS Approach to Mediation: Data Models and Languages". In Proceedings of IPSJ, Tokyo, Japan, October 1994.

....The work will extend on research developed at Uppsala Database Laboratory (http: www.dis.uu. se udbl) on OO queries over distributed and heterogeneous data [41, 42, 32] Research from other institutes on wrapping and searching heterogeneous, distributed, and semistructured data, e.g. [15, 23, 40], is also applicable. Other important supplemental components are user interface modules for subject oriented visual query specifications and for visualizing retrieved learning objects, which can be added as plugins. Dissemination, Testbeds and Evaluation In the project we will implement a ....

H. Garcia-Molina, Y. Papakonstantinou, D. Quass, A. Rajaraman, Y.Sagiv, J. Ullman, V. Vassalos, and J. Widom. The tsimmis approach to mediation: Data models and languages. Intelligent Information Systems (JIIS), Kluwer, 8(2):117--132, 1997.

....variables can be created from meta variables during problem solving. However, no representation that allows the distribution of knowledge over several agents has been presented so far. The proposed architecture for distributed configuration relates to previous research projects such as TSIMMIS [5] or Infomaster [6] They provide an integrated access to multiple distributed heterogenous information sources on the Internet. Our approach for distributed configuration goes a step further, because not only information sources but problem solving agents with local knowledge are integrated, thus ....

H. Garcia-Molina, Y. Papakonstantinou, D. Quass, A. Rajaraman, Y. Sagiv, J. Ullman, V. Vassalos and J. Widom. The TSIMMIS Approach to Mediation: Data Models and Languages. Journal of Intelligent Information Systems, 8(2):117--132, 1997.

....0 containing information relevant in order to answer Q. We have not developed yet a query planer, because our main purpose was the foundation of the algorithm. Future works will be studying the applicability of existing query planners in our algorithm, and possible extensions of them. In TSIMMIS [ 7 ] a common model, called OEM, and a speci c query language, called LOREL, are used for interrogating the system. Mediators perform query propagation, query interpretation, result propagation and result interpretation. Di erently from Information Manifold, the common model is a very simple one. The ....

H. Garcia-Molina, Y. Papakonstantinou, D. Quass, A. Rajaraman, Y. Sagiv, V. Vassalos, and J. Widom. The TSIMMIS Approach to Mediation: Data Models and Languages. Journal of Intelligent Information Systems, 8(2), 1997.

....speci cation for HTML pages is either a set of rules or a query in some query language designed for wrapping. The wrappers are built semi automatically or automatically from these speci cations using a special tool or a programming language. For heterogenous data sources systems like TSIMMIS [GMP95] and MIX [BGL99] have been developed with the approach of using a query language for the wrapper speci cation. The work of Nakhimovsky [Nak01] is perhaps the closest to our view of describing and implementing wrappers: while he uses formal grammars and parser generators to create a skeleton parser ....

H. Garcia-Molina, Y. Papakonstantinou, D. Quass, A. Rajaraman, Y. Sagiv, J. Ullman, V. Vassalos, and J. Widom. The TSIMMIS approach to mediation: Data models and languages. In Conference proceedings of the NGITS (Next Generation Information Technologies and Systems), Naharia, Israel, June 27-29

....value, object id) is well suited for information exchange in heterogeneous and dynamic environments. TSIMMIS query processing lies on pre defined query pattern matching. The query reformulation is performed by logic (first order predicates) rewriting rules against the pre defined query patterns [GARC97]. In the SIMS project, a domain model (shared ontology) of the application domain is designed : it establishes a fixed vocabulary describing objects in the domain, their attributes and their relationships [AREN96] The SIMS project uses the LOOM (knowledge logic language) knowledge representation ....

GARCIA-MOLINA H.& AL. --- The TSIMMIS Approach to Mediation : Data Models and Languages, in Journal of Intelligent Information Systems 8, pp 117-132, (1997).

....supported by all wrapper agents in order to support query answering. A rst implementation of these tasks, which is correct and complete w.r.t. the formal model, is also presented. 1 Introduction Several reference architectures for information integration have been proposed in the literature [8, 6, 2]. In most of them the key role is played by a mediator, that provides an homogeneous and global model of the di erent information sources, and enables global applications to access the di erent information sources in a transparent way. Mediators suitably distribute queries to the relevant ....

....source S 0 containing information relevant in order to answer Q. We have not developed yet a query planer, because our main purpose was the foundation of the algorithm. Future work will study the applicability (and possible extensions) of existing query planners to our algorithm. In TSIMMIS [6] a common model, called OEM, and a speci c query language, called LOREL, are used for interrogating the system. Mediators perform query propagation, query interpretation, result propagation and result interpretation. Di erently from IM, the common model is very simple. The main idea is that all ....

H. Garcia-Molina, Y. Papakonstantinou, D. Quass, A. Rajaraman, Y. Sagiv, V. Vassalos, and J. Widom. The TSIMMIS Approach to Mediation: Data Models and Languages. Journal of Intelligent Information Systems, 8(2):117-132, 1997.

....[Beeri et al. 1997; Kirk et al. 1995; Ullman, 1997] the problem of query containment corresponds to the subsumption problem. There are two basic approaches to intelligent information integration: the procedural approach and the declarative approach. In the procedural approach (e.g. TSIMMIS [GarciaMolina et al. 1997] ) mediators integrate information from sources through ad hoc procedures defined with respect to a set of predefined information needs. When such needs or sources change (i.e. we have a dynamic information system) a new mediator must be generated. In the declarative approach (e.g. SIMS [Arens ....

H. Garcia-Molina, Y. Papakonstantinou, D. Quass, A. Rajaraman, Y. Sagiv, J. Ullman, V. Vassalos, and J. Widom. The TSIMMIS approach to mediation: data models and languages. Journal of Intelligent Information Systems, 8:117--132, 1997.

....Further this knowledge may only be partially shared among business partners for reasons of privacy and security. Therefore, we have to enable current configuration technology towards co operative problem solving. Our proposed architecture relates to previous research projects such as TSIMMIS in [7] or Infomaster from [8] where an integrated access to multiple distributed and heterogeneous information sources on the internet is provided. As Figure 1 depicts, in our approach not only information sources but problemsolving agents with local knowledge (Configuration KB) are integrated. The ....

Garcia-Molina, H., Papakonstantinou, Y., Quass, D., Rajaraman, A., Sagiv, Y., Ullman, J., Vassalos, V., and Wisom, J., The TSIMMIS Approach to Mediation: Data Models and Languages. Journal of Intelligent Information Systems, Vol. 8(2), 1997, pp. 117-132.

....databases and general query processing. There has been several projects on integration of data in a multi database environment [22 31] The integration facilities of AMOS II are based on work in the area of OO views [32 39] Most of the mediator frameworks reported in the literature (e.g. [26,31,40]) propose centralized query compilation and execution coordination. In [41] it is indicated that a distributed mediation framework is a promising research direction, but to the best of our knowledge no results in this area are reported. Some recent commercial data integration products, such as ....

Garcia-Molina H, Papakonstantinou Y, Quass D, Rajaraman A, Sagiv Y, Ullman J, Vassalos V, Widom J. The TSIMMIS approach to mediation: Data models and languages. Intelligent Information Systems 1997; 8(2):117--132.

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H. Garcia-Molina, Y. Papakonstantinou, D. Quass, A. Rajaraman, Y. Sagiv, J. Ullman, V. Vassalos, and J. Widom. The TSIMMIS Approach to Mediation: Data Models and Languages. Journal of Intelligent Information Systems, 8(2), 1997.

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H. Garcia-Molina, Y. Papakonstantinou, D. Quass, A. Rajaraman, Y. Sagiv, J. Ullman, V. Vassalos, and J. Widom. The TSIMMIS Approach to Mediation: Data Models and Languages. Journal of Intelligent Information Systems, 8(2), 1997.

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H. Garcia-Molina, Y. Papakonstantinou, D. Quass, A. Rajaman, Y. Sagir, J. Ullman, V. Vassalos, and J. Widom. The TSIMMIS approach to mediation: Data models and Languages. Journal of Intelligent Information Systems, 1997. (See also http://wwwdb. stanford.edu/tsimmis/). 17

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H. Garcia-Molina, Y. Papakonstantinou, D. Quass, A. Rajaraman, Y. Sagiv, J. D. Ullman, V. Vassalos, and J. Widom. The TSIMMIS Approach to Mediation: Data Models and Languages. Journal of Intelligent Information Systems, 8(2):117--132, March/April 1997.

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H. Garcia-Molina, Y. Papakonstantinou, D. Quass, A. Rajaraman, Y. Sagiv, J. Ullman, and J. Widom, The TSIMMIS Approach to Mediation: Data Models and Languages, presented at Proc. International Workshop on Next Generation Information Technologies and Systems, Naharia, Israel, 1995.

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Garcia-Molina , Y. Papakonstantinou , D. Quass , A. Rajaraman , Y. Sagiv , J. Ullman , V. Vassalos , J. Widom (1996). The TSIMMIS approach to mediation: Data models and Languages. Journal of Intelligent Information Systems.

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H. Garcia-Molina, Y. Papakonstantinou, D. Quass, A. Rajaraman, Y. Sagiv, J. Ullman, V. Vassalos, and J. Widom. The TSIMMIS Approach to Mediation: Data Models and Languages. Journal of Intelligent Information Systems, 8(2), 1997.

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H. Garcia-Molina, Y. Papakonstantinou, D. Quass, A. Rajaraman, Y. Sagiv, J. Ullman, and J. Widom. The TSIMMIS Approach to Mediation: Data Models and Languages. In Proceedings of NGITS (Next Generation Information Technologies and Systems), 1995.

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