E. Pitoura, O. Bukhres, and A. Elmagarmid. Object orientation in multidatabase systems. ACM Computing Surveys, 27(2):141--195, June 1995.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....as an implementation base for various applications of information fusion. 3 Federated Database Technology in Information Fusion Technologies from the federated database eld could ful ll an essential part of the discussed requirements. Federated database design concerns with schema integration [3, 15, 4] and integrity constraints; FDBS components support transparent data access and manipulation [7] as well as translation and optimization of queries [14] For fusion applications the most important tasks are as follows: Intelligent support of integration: In many cases the integration of the ....

E. Pitoura, O. Bukhres, and A. K. Elmagarmid. Object Orientation in Multidatabase Systems. ACM Computing Surveys, 27(2):141-195, 1995.

....and conceptualizations employed by the various information providers and consumers. Providing access to heterogeneous and distributed databases through integrated views has been studied from the early 80 s [6] A large number of papers exist on the integration of distributed databases and [36,46,43] are comprehensive studies on the topic. However such approaches for data This work was partially supported by the European project C Web (IST1999 13479) The work of this author was supported by a fellowship from the TMR European Network Chrorochronos. integration are not appropriate ....

E. Pitoura, O.A. Bukhres, and A.K. Elmagarmid. Object orientation in multidatabase systems. ACM Computing Surveys, 27(2):141--195, June 1995. Bernd Amann et al.: Integrating ontologies and thesauri

....instead of the join equivalences used (Section 4.2) 6 Related Work The general notion of software external to the DBMS participating in query processing is classic. Much work has been done on heterogeneous databases [HK89, ERS95, OV99] also called federated databases [SL90] or multidatabases [PBE95]) in which data resident in multiple, not necessarily consistent databases is combined for presentation to the user [RH98, YM98] This approach shares much with the notion of temporal middleware: the underlying database cannot be changed, the data models and query languages exposed to the users ....

E. Pitoura, O. Bukhres, and A. Elmagarmid. Object Orientation in Multidatabase Systems. ACM Computing Surveys, 27(2): 141--195 (1995).

....data access to accomplish query formulation, users must have information about the distribution and the semantics of data. Distributed Object Management (DOM) Another way to model heterogeneous distributed systems is to represent the resources of the system as a collection of interacting objects (PITOURA, 1995; ZU, 1994; MANOLA et al. 1992) Each component system defines a service interface and provides the implementation of such services. The OMA (OMG, 1995) architecture and the ODMG (CATTEL, 1997) model are important research works devoted to this approach. MIND METU Interoperable DBMS (DOGAC ....

PITOURA, E., BUKHERS, O., ELMAGARMID, A., 1995, "Object Orientation in Multidatabase Systems". In: ACM Computing Survey, v.27(2), Jun.

....5 we sketch basic principles of a method which we are currently developing for resolving conflicts as part of data integation. Finally, Section 6 concludes the paper and outlines future work. 2 Related Work The more general problem of schema integration is addressed by several approaches [BLN86,PBE95] For describing conflicts arising in the integration phase various classifications were developed, e.g. in [KS91,SCG93,SPD92] Data models and query languages supporting the integration of heterogeneous sources are particularly multidatabase languages like MSQL [GLRS93] SQL M [KGK 95] and ....

E. Pitoura, O. Bukhres, and A. K. Elmagarmid. Object Orientation in Multidatabase Systems. ACM Computing Surveys, 27(2):141--195, June 1995.

....can be resolved by transforming the local schemata into the canonical data model of the FDBS. In the second step schematic heterogeneity is solved. In general, this step is a very complex task due to many kinds of conflicts. Therefore, different integration methodologies were proposed in [2, 12, 21, 7, 15, 14]. There are different requirements attributed to the integration of local schemata into an integrated schema (adopted from [2] page 337) ffl Completeness and Correctness : The integrated schema must contain all concepts present in any component schema correctly. The integrated schema must be a ....

....all new buildings (S1.Buildings not specialized to old buildings) are included in the second database as habitable buildings. S1.Building: S1.Old Building: S2.Building: S2.Habitable Building: 1 2 3 4 5 Figure 2: Extensional Overlapping of Input Classes Most existing integration approaches [13, 12, 21, 3, 7, 22, 15, 8, 14] do only mark pairs of classes with a possibly non empty population intersection as candidates for integration. Additionally, attributes may be marked to be corresponding. The resulting integration assertions can be listed in the notation proposed by [22] S1fflBuilding S2fflBuilding ....

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E. Pitoura, O. Bukhres, and A. K. Elmagarmid. Object Orientation in Multidatabase Systems. ACM Computing Surveys, 27(2):141--195, June 1995.

....schemata is how to correctly deal with the heterogeneity. Data model heterogeneity can be resolved by transforming each local schema into the canonical data model. After that schema heterogeneity has to be overcome. Many methodologies were proposed (e.g. BLN86, LNE89, SPD92, Dup94, RPRG94, PBE95] which describe various conflict resolution techniques. In order to support logical data independence, different external schemata must be derivable from the integrated schema. From now on, we refer to such views as external integrated schemata. The generation of a view has to fit to the ....

....the right canonical data model can be found in [SCG91] The choice of the canonical data model influences the quality of the integration step, which is the most difficult step of the design process. Most of the recent proposals prefer an object oriented data model (e.g. in [TS93, RPRG94, GCS95, PBE95, Bra93] It is often argued that only a semantically rich data model can be the right canonical data model because no or only little semantics is lost during the transformation from an object oriented local schema to the canonical data model (see also [SCG91] Instead, we propose the use of a ....

E. Pitoura, O. Bukhres, and A. K. Elmagarmid. Object Orientation in Multidatabase Systems. ACM Computing Surveys, 27(2):141--195, June 1995.

....For a data model to t as a CDM, Saltor et. al [SCG91] suggest that it should have two properties: Expressiveness, and Semantic Relativism. Especially for schema integration they argue that data models should support views. Views are also discussed as an enhancement to to models by Pitoura et. al [PBE95] and we therefore add it as an additional requirement. We summarize the three requirements in table 2.2 and describe them in the following. Requirements for a canonical data model RCDM 1 Expressiveness RCDM 2 Semantic Relativism RCDM 3 Support for Views Table 2.2: Requirements for a ....

....to them. The denition of a view is dependent upon the data model and the facilities of the language used to specify the view. Object oriented views are in general dened by a set of virtual classes that are populated by existing objects or by imaginary objects constructed from existing objects ( PBE95] In general, the object oriented models lacks some necessary mechanisms for grouping already existing objects and we need therefore to dene a suitable way to dene and express views. 2.6 Schema Integration As we mentioned in section 2.4.1 the three key issues were; constructing a global schema ....

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Evaggelia Pitoura, Omran Bukres, and Ahmed Elmagarmid. Object Orientation in Multidatabase Systems. ACM Computing Surveys, 27(2):141195, June 1995.

....often appears to be a main component of conceptual design which is itself a part of the overall activity of software design. This explains the significant interest in schema integration methodologies: a vast diversity of various approaches, techniques and tools were proposed (see, eg, surveys [1, 11, 10]) Moreover, to date the value of the issue has increased greatly due to the tendency of organizing modern (and of the nearest future) information systems into federal environments where schema and data integration are among primary questions. The main difficulty in view integration consists in ....

E. Pitoura, O. Bukhres, and A. Elmagarmid. Object orientation in multidatabase systems. ACM computing surveys, 27(2):141--195, 1995.

....integrated with specific products. This means that the format might change in any new version of the product and render existing database components obsolete. Interoperability is the general term for describing issues concerning the cooperation of software in the joint execution of a task [22]. Building systems that combine resources and services in a distributed and heterogeneous environment raises a number of new issues concerning the exchange, modification (transaction management) integration (semantic interoperability) and querying of distributed data. All of these issues depend ....

....window. 6. Future Work The Mediated Perspective A different solution to the problem of integrating software components is the definition of a mediator based architectures [25] where applications access data via data access providers [9] which play the role of mediators, global layers [22] or master components [2] Mediators break the strong coupling between servers and clients, caused by low level interfaces allowing only restricted forms of abstraction. They are generally based on common data models restricted to some application domain and include various information processing ....

Pitoura, E., Bukhres, O., and Elmagarmid, A. Object orientation in multidatabase systems. ACM Computing Surveys 27, 2 (June 1995), 141--195.

....that suggests quite new methodologies for the area. In [8, 15] we described how a bit more involved algebraic machinery solves the problem of heterogeneuos schema integration which for a long time was a challenge for information modeling methodologies and tools (see, eg, the recent survey [33]) The present paper reviews the machinery from a more refined algebraic standpoint and motivates a framework which might be entitled Algebraic graph based model theory for databases (cf. 11] The term schema (or, sometimes, view) integration refers to the activity aimed at producing a global ....

....conceptual design which is itself a part of the overall activity of database design. This explains the significant interest in schema integration methodologies: a vast diversity of various approaches, techniques and sometimes tools were proposed (see, eg, 10, 30, 42, 43, 40, 39, 36] and surveys [4, 37, 33]) Moreover, to date the value of the issue has increased greatly due to the evident tendency of organizing modern (and of the nearest future) information systems on cooperative federal principals. Indeed, in the context of federated database systems (FDBS) integration is a function regularly ....

[Article contains additional citation context not shown here]

E. Pitoura, O. Bukhres, and A. Elmagarmid. Object orientation in multidatabase systems. ACM Computing Surveys, 27(2):141--195, 1995.

..... translate each subquery into a request that can be answered by the source . submit the translated subqueries and . collect and merge the results. The last decade has seen a number of projects addressing the integration of semantically and schematically heterogeneous databases (for instance [26, 23, 13, 10]) One important issue in this area that in our mind was not yet considered sufficiently is maintainability. Maintainability appears in various aspects. First, the global level should be protected against changes inside the sources as much as possible, enabling their independent evolution. Second, ....

Pitoura, E., O. Bukhres, et al. (1995). "Object Orientation in Multidatabase Systems." ACM Computing Survey 27(2): 141-195.

.... Research on semantic interoperability is relatively recent with the development of networks and networks and groupware tools [5] Its tries to benefit from a large body of knowledge and experience in the field of program translation, and more recently of access to multiple heterogeneous databases [6 8]. The Challenge of Semantic Interoperability in Health Information Systems Semantic interoperability issues are likely to increase exponentially with the rapid development and internetworking of existing information systems. Here are some of the main reasons. Current health informatics ....

....developers need to share the knowledge of semantics of data that is hidden in the data dictionary associated with the data server. In a multidatabase system, a common object model might facilitate the access to the different pieces of information that are stored in the heterogeneous environment [6 8]. The functional architecture of a semantic interoperability mediator Argument Describers and Descriptors For each atomic element that composes the message, it is necessary to vehicle the meaning of the possible values. The representation of this knowledge is called an argument descriptor. For ....

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Pitoura E, Bukhres O, Elmagarmid A. Object orientation in multidatabase systems. ACM Computing Surveys 1995; 27 (2): 141--95.

....repositories of data, and the proliferation of computer networks worldwide is providing universal access to countless sources of heterogeneous databases, which are created and administered by a wide range of organizations. Several surveys of heterogeneous multidatabase systems are available [4, 20, 27, 31, 36, 40]. Two important challenges are: 1) to develop techniques to integrate semantically heterogeneous schemas from existing databases into a single, uniform schema; and 2) to translate queries expressed in terms of the integrated schema into queries that may be evaluated against the existing ....

E. Pitoura, O. Bukhres, and A. Elmagarmid. Objectorientation in multidatabase systems. ACM Computing Surveys, 27(2), June 1995.

....Representative examples of system components in geographic applications are database management systems, modeling systems and graphical user interfaces. Interoperability has become the general term for describing issues concerning the cooperation of software in the joint execution of a task [18]. Building systems that combine resources and services in a distributed and heterogeneous environment raises a number of new issues concerning the exchange, modification (transaction management) and integration (semantic interoperability) of distributed data. All of these issues depend on the ....

.... A Mediator Based Architecture for GIS Data heterogeneity is an essential issue to existing and future GIS applications and can be solved by adopting a layered architecture as it is proposed by the Open Geodata Interoperability Specification (OGIS) 4, 12] in general distributed database systems [20, 18], and in heterogeneous multimedia information systems (e.g. TSIMMIS [7] and Garlic [5] An example of a system implementing the different layers of such an architecture is shown in Figure 1. C2 C1 7 3 6 2 5 1 1 4 Applications Data Access Providers Database Layer FS W1 W2 W3 DB1 ....

[Article contains additional citation context not shown here]

E. Pitoura, O.A. Bukhres, and A.K. Elmagarmid. Object orientation in multidatabase systems. ACM Computing Surveys, 27(2):141--195, June 1995.

....a canonical data model. In the second step schematic heterogeneity has to be overcome. In general, this step is a very complex task due to many kinds of conflicts. Therefore, different integration methodologies were proposed in [BLN86, NEL86, LNE89, SP94, SPD92, Bra93, TS93, Dup94, RPRG94, GCS95, PBE95] There are different requirements attributed to the integration of local schemata into an integrated schema (adopted from [BLN86] page 337) ffl Completeness and Correctness: The integrated schema must contain all concepts present in any component schema correctly. The integrated schema must ....

....the second database as habitable buildings. Extensional Overlappings S1.Building: S1.Old Building: S2.Building: S2.Habitable Building: 1 2 3 4 5 Figure 2: Extensional Overlapping of Input Classes Most existing integration approaches [NEL86, LNE89, SPD92, Bra93, Dup94, SP94, RPRG94, GCS95, PBE95] do only mark pairs of classes with a possibly non empty population intersection as candidates for integration. Additionally, attributes may be marked to be corresponding. The resulting integration assertions can now be listed in the notation proposed by [SP94] S1fflBuilding S2fflBuilding ....

[Article contains additional citation context not shown here]

E. Pitoura, O. Bukhres, and A. K. Elmagarmid. Object Orientation in Multidatabase Systems. ACM Computing Surveys, 27(2):141--195, June 1995.

....can be incorporated into the multidatabase system by providing an object oriented interface between such sources and the global schema. The use of the object oriented model as a canonical model and language for interface definitions has been widely addressed and supported in the literature [17, 7, 2, 19, 16, 22]. The advantages of having a canonical object model integrating heterogeneous data sources include a common methodology for modeling and querying, encapsulation, inheritance, coupling and modular extension. In Donaj i, semantic information about the structure and organization of the data in the ....

....data source LS2; and class PUBLICATION is taken from a local data source LS3. The process of integration and creation of the GCS is not considered in this paper. We assume that it has been performed following one of any of the object oriented integration techniques well addressed in the literature [7, 2, 16, 22]. We consider that the result of the integration process is a GCS similar to Figure 5.2. However, implicit in the GCS may be classes that contain attributes making reference to classes taken from other sources (virtual relationships, denoted by thin dashed arrows) The GCS may also contain ....

Pitoura, E., Bukhres, O., Elmagarmid, A., "Object Orientation in Multidatabase Systems," ACM Computing Surveys, Vol. 27, No. 2, June 1995, pp. 141-195.

....between all the component system representations. The chosen CDM is best if it is a canonical data model and expressive enough to capture the meaning of all local data models [CAS94, HUL87, SAL91] The OO data model is a suitable CDM and has been used for this purpose in several projects (e.g. [BER94, FAH94, PIT95]) Query language heterogeneity can be resolved by providing transparent query translators. This means that a user can use his her local query language to formulate a query, and this query will subsequently be translated (and divided into sub queries for different databases, if necessary) by the ....

....3.3 Object Orientation and Multidatabase Systems This section shows how object orientation has shaped current MDB systems in terms of their architectures and CDMs. 3.3. 1 Object Based Multidatabase Systems The application of the OO paradigm in MDB architectures is advocated by many authors [NIC93, PIT95] as it provides a natural model for heterogeneous, autonomous and distributed systems. This model is called the Distributed Object Architecture (DOA) The constituent components of the MDB are treated as large grained objects, where each of them is presented to the MDB system as an object with a ....

[Article contains additional citation context not shown here]

E. Pitoural, O. Bukhres and A. Elmagarmid. Object-Orientation in Multidatabase Systems. ACM Computing Surveys, 27(2), pages 141--195, 1995.

....[26] to design the Generative Communication Service. Our research is based in a healthcare multidatabase environment. We assume a multidatabase or federated database system to refer to a loose coupling of participating heterogeneous database systems. We will use the terminology in [27] and [24] when referring to the multidatabase architecture and components. We have the following problem to consider: two autonomous databases have a requirement to exchange information in a multidatabase environment. They wish to pass information objects using a communication service that should not need ....

E. Pitoura, O. Bukhres, and A. Elmagarmid. Object orientation in multidatabase systems. ACM Comput. Surv., 27(2):141--195, June 1995.

....as an implementation base for various applications of information fusion. 3 Federated Database Technology in Information Fusion Technologies from the federated database field could fulfill an essential part of the discussed requirements. Federated database design concerns with schema integration [3, 15, 4] and integrity constraints; FDBS components support transparent data access and manipulation [7] as well as translation and optimization of queries [14] For fusion applications the most important tasks are as follows: Intelligent support of integration: In many cases the integration of the ....

E. Pitoura, O. Bukhres, and A. K. Elmagarmid. Object Orientation in Multidatabase Systems. ACM Computing Surveys, 27(2):141--195, 1995.

....a proper repre defines Data source Data source Data source UAL with integrated views Query processing: Decomposition . Translation . Result integration View definition User Classification Criteria for Federated Information Systems 13 Federated Information Systems April 1999 sentation [PBE 95] HP 96] SCG 91] Note that the table assumes that it is tried to properly integrate data, i.e. without loss in semantic, and ignores e.g. the possibilities of canonical schemas. 3.4 Kinds of semantic integration The integration layer encapsulates data sources for the user. In contrast to ....

E. Pitoura, O. Bukhres, A.K. Elmagarmid, Object Orientation in Multidatabase Systems, ACM Computing Surveys, Vol. 27, No. 2, pp. 141-195, Jun. 1995.

....of data occurs on remote databases, they are transmitted to the warehouse. Incremental view maintenance techniques are used to maintain the views consistent with the modifications. Multidatabase systems are confederations of pre existing, autonomous and possibly heterogeneous database systems [32]. The pre existing database systems that participate in the multidatabase are called local or component database systems. Usually the term multidatabase denotes nonfederated systems that integrate various heterogeneous database systems by supplying a common query language for specifying queries ....

....of InterBase KB with our previous research. 3 2.1 Schema Integration There are two broad categories for integrating the schemata of individual, heterogeneous databases. Object Oriented (common) data model. Most of the existing approaches for schema integration belong to this category [32, 21, 20, 3, 10]. The databases participating in the federation are mapped to a common data model, which most commonly is object oriented that acts as an interpreter among them. Furthermore, a common view that hides the structural differences on the schemas of the heterogeneous databases offers integration ....

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E. Pitoura, O. Bukhres, and A. Elmagarmid, "Object Orientation in Multidatabase Systems," ACM Computing Surveys, Vol. 27, No. 2, 1995, pp. 141-195.

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E. Pitoura, O. Bukhres, and A. Elmagarmid. Object orientation in multidatabase systems. ACM Computing Surveys, 27(2):141--195, June 1995.

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E. Pitoura, O. Bukhres, and A. Elmagarmid. Object Orientation in Multidatabase Systems. ACM Computing Surveys, 27(2): 141--195 (1995).

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E. Pitoura, O. Bukhres, and A. Elmagarmid. Object Orientation in Multidatabase Systems. ACM Computing Surveys, 27(2), June 1995.

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