F. Saltor, M. Castellanos, and M. Garca-Solaco. Suitability of data models as canonical models for federated databases. SIGMOD Record, 20(4):45--48, 1991.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....in loosely coupled FDBS are discussed, for example, in [Wie92, ZHK96] Very important for a schema integration is the choice of the right common data model in which the schema integration is performed. The suitability of different data models as common data model is discussed in [BLN86, SCG91, HB96] The favorite data model is usually an object oriented data model due to its semantical richness. As common data model for homogenization in the GIM approach we use the Generic Integration Model GIM which enables an efficient algorithm to derive an integrated schema in a user friendly data ....

F. Saltor, M. Castellanos, and M. Garcia-Solaco. Suitability of Data Models as Canonical Models for Federated Databases. ACM SIGMOD Record, 20(4):44--48, December 1991.

....been tailored to loosely coupled systems (which do not fit with the architecture that is required for MIGI) and are based on schema translation. However, a global object oriented data model and operational integration are essential to cope with heterogeneous component systems ( GaCO90] 6 [Salt91]. Most GIS do not support the database concept schema, and their data can only be accessed via application programming interfaces. Therefore, the schema translation approach is not appropriate for integrating spatial data. Summing up, MIGI has to develop its own integrity control concept which ....

F. Saltor et al. Suitability of data models as canonical models for federated databases. SIGMOD Record, 20(4), December 1991.

....Granada (Spain) has been researching on these topics since 1986. Main results of the BLOOM research group since 1986 include (see the Web page http: wwwlsi. upc.es bloom home.html for details) Development of a framework of characteristics of a data model that make it suitable as CDM of a FIS [SCG91]. Development of the BLOOM data model to satisfy all these characteristics [CSG92] Classification of semantic heterogeneities [GSC96] Semantic enrichment of schemas [CSG94] Detection and resolution of semantic heterogeneities [SCRR96] GSC96] Development of a 7 level schema ....

Saltor, Castellanos & Garca-Solaco: "Suitability of Data Models as Canonical Models for Federated DBs". ACM SIGMOD Record vol 20(4), pp 44-48 (special refreed issue: A. Sheth (ed.): Semantic Issues in Multidatabase Systems, December 1991).

....access, as explained in [SR99] it is necessary to overcome semantic heterogeneities, and represent related concepts. This is accomplished through an integration process in which a Canonical Data Model (CDM) plays a central role. Once argued the desirable characteristics of a suitable CDM in [SCGS91], and after stating that existing models did not satisfy these characteristics, the BLOOM model (BarceLona Object Oriented Model) was progressively defined in [CKSGS94] and [GSSC95] among others. It results in an extension of an object oriented model with a semantically rich set of abstractions. ....

F. Saltor, M. Castellanos, and M. Garc'ia-Solaco. Suitability of Data Models as Canonical Models for Federated DBs. ACM SIGMOD Record, 20(4):44-- 48, 1991.

....a document as such, i.e. the container, rather than the data themselves. PDM systems are also inferior to FDBMS in many other aspect, most notably, transparent, homogeneous access to distributed, heterogeneous data. A 5 level schema architecture [16] and an objectoriented global data model [12] are generally accepted for most FDBMS [4] 2] proposes operational integration to cope with a high degree of heterogeneity of the component systems. This is applied in [8] to introduce usability specifications to non versioned object types such that even objects from component systems with weak ....

F. Saltor, M. G. Castellanos, and M. Garca--Solaco. Suitability of data models as canonical models for federated databases. SIGMOD Record, 20(4):44--48, Dec. 1991.

....recent proposals prefer an object oriented data model. 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 [16]) On the other hand, a semantically rich data model causes more heterogeneity on the schema level than a semantically poor data model does (cf. 2] This heterogeneity on schema level in turn increases the complexity of the integration process (cf. object oriented integration methodologies ....

F. Saltor, M. Castellanos, and M. Garcia-Solaco. Suitability of Data Models as Canonical Models for Federated Databases. ACM SIGMOD RECORD, 20(4):44--48, December 1991.

....able to influence the derivation of their external integrated schemata. 2 Generic Integration Model The right choice of the canonical data model is essential to the design process of a federated database system (FDBS, cf. SL90] A discussion about 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 ....

.... 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 canonical data model which is semantically poor. On the basis of the semantically poor data model GIM, abbreviation of Generic Integration Model, we propose an algorithm which generates external object oriented schemata automatically. In this way we do not ....

F. Saltor, M. Castellanos, and M. Garcia-Solaco. Suitability of Data Models as Canonical Models for Federated Databases. In J. Clifford and R. King, editors, Proc. of the 1991 ACM SIGMOD Int. Conf. on Management of Data, Denver, Colorado, SIGMOD RECORD 20(2), pages 44--48. ACM Press, June 1991.

....datatype of the component database models should have a natural analogue in the meta datamodel. Further, such a model should be sufficiently simple and expressive as to allow data to be represented in multiple ways so that conflicts between alternative representations of data can be resolved. In [39] the requirements on a model for transforming heterogeneous databases are examined, and the authors conclude that a model supporting complex data structures (sets, records and variants) object identity and specialization and generalization relations between object classes is desirable. Person ....

F. Saltor, M. Castellanos, and M. Garcia-Solaco. Suitability of data models as canonical models for federated databases. SIGMOD Record, 20(4):44--48, December 1991.

....consequence of the use of dioeerent native data models. The CDM must be chosen according to requirements for suitability in such a system. This is discussed next. 2.5. CANONICAL DATA MODEL 23 2.5.1 Requirements for a Canonical Data Model 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 ....

....mechanism adds AEexibility to the model, since it allows arbitrary renements of the model itself, e.g. additions of new relationships. As we discussed in section 2.5 the canonical model should have the properties of expressiveness, semantic relativism, and support for views. Saltor et. al [SCG91] argue that object oriented models are among the best suited models to serve as a canonical model in that they meet the two rst required properties to a better degree than other models. The only lack of essential properties, according to Saltor et. al [SCG91] is that they don t support views as ....

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F. Saltor, M. Castellanos, and M. Garc#a-Solaco. Suitability of Data Models as Canonical Models for Federated Databases. ACM SIGMOD Record, 20(4):44 48, December 1991.

....object migration also instead to local object l2. What data migrates of an object depends on the canonical data model of the FDBS and the object definition within this data model. Our solution is based on an object oriented data model fulfilling the requirements for an FDBS canonical data model [15]. An upcoming standard for an object oriented data model is fixed in [14] with the following object notion: An object consists of several attributes that express its structure (data attributes and relationships) and owns some methods describing the object s behavior. To formally define the ....

SALTOR F., CASTELLANOS M., GARCIA-SOLACO M. Suitability of data models as canonical models for federated databases. SIGMOD RECORD 20(4), pages 44--48, 1991.

....value problems. Data model problems occur, if the data model of the old system is different from the data model of the new one (e.g. migrating from a hierarchical data model to a relational one) In these cases, a translation of the different data models into a common data model has proven useful [21]. This class of problems is beyond the scope of this paper. The remaining two classes, data definition problems and data value problems are strongly interrelated, i.e. changes in the definition of an attribute also demand data values to be changed. Data definition problems have to be solved ....

Saltor, F.: Suitability of Data Models as Canonical Models for Federated Databases. Sigmod Record, 20, 1991.

....control documents, i.e. containers, rather than the data themselves. PDM systems are also inferior to FDBMS in many other aspect, most notably, transparent, homogeneous access to distributed, heterogeneous data. A 5 level schema architecture [SL90] and an object oriented global data model [SCG91] are generally accepted for most FDBMS [CEH 97] BNPS88] proposes operational integration to support a high degree of heterogeneity of the component systems. This is applied in [HD92] to introduce usability speci cations to non versioned object types such that even objects from component ....

F. Saltor, M. G. Castellanos, and M. Garca{Solaco. Suitability of data models as canonical models for federated databases. SIGMOD Record, 20(4):44-48, December 1991.

....recent proposals prefer an object oriented data model. 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] On the other hand, a semantically rich data model causes more heterogeneity on the schema level than a semantically poor data model does (cf. BLN86] This heterogeneity on schema level in turn increases the complexity of the integration process (e.g. object oriented integration methodologies ....

F. Saltor, M. Castellanos, and M. Garcia-Solaco. Suitability of Data Models as Canonical Models for Federated Databases. In J. Clifford and R. King, editors, Proc. of the 1991 ACM SIGMOD Int. Conf. on Management of Data, Denver, Colorado, SIGMOD RECORD 20(2), pages 44--48. ACM Press, June 1991.

....(DDTS [23, 91] Relational (MERMAID [14, 91, 104] DATAPLEX [14, 26, 104] ADDS [14, 104] Functional (MULTIBASE [14, 23, 91, 97, 104] Object Oriented (PEGASUS [1, 57] Heimbigner [14, 48] Hammer et al. 44, 45, 37, 38] ERC (Tari [103] and so on. As outlined by Saltor et al. [88] a data model is responsible for the representation ability of a database which is composed of two factors: expressiveness and semantic relativism. Expressiveness means the degree that a data model can represent the conceptualisation of the reality aspects. It is composed of structural and ....

....believe that an o o data model is suitable as a canonical data model. At the federation level it is necessary a strong notion of identity (the property that distinguishes an object from all other objects in the system) and object oriented data models support this identity notion. Saltor et al. [88] developed a framework to analyse what are the characteristics that a data model should have to be suitable to be used as a canonical data model. They conclude that the hierarchical and network models are not suitable. On the other hand, the ER model and its extensions are inferior when compared ....

F. Saltor, M. Castellanos, and M. Garcia-Solaco. Suitability of data models as canonical models for federated databases. SIGMOD RECORD, 20(4):44--48, December 1991.

....model (CDM) representation reduces the number of translators needed compared with an approach based on translating directly 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 ....

....requires a good understanding of the meaning of data (i.e. how data is interpreted by database administrators, application programs and end users) and it also evolves with time. Unfortunately, it is not possible to fully capture real world semantics by using available data modelling techniques [SAL91]. Therefore, nearly all tools that deal with detecting and reconciling semantic heterogeneity depend on user interaction to complement and validate their results [GAR96, GOT92, KIM91a, KIM93, SPA91, SAV91] 2.4.1 Heterogeneity Aims for MVDS Heterogeneity is a natural consequence of progress and ....

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F. Saltor, M. Castellanos and M. Garcia-Solaco. Suitability of Data Models as Canonical Models for Federated Databases. SIGMOD RECORD, 20(4), pages 44--48, 1991.

....CDBS (CR2, CR7) e.g. with hierarchical, network, relational, and object oriented DBS, or file systems. Moreover they transform the heterogeneous data and operations into a canonical data model (CR3, CR5) Our approach considers an object oriented canonical data model due to its expressive power [14]. It is based on the upcoming standard for object oriented database systems, the ODMG object model [1] which provides concepts like objects, classes, class inheritance, object identity. To ease the dynamic extension of the federation with new DBS, there is a uniform layer (DB coupling) on top of ....

SALTOR F., CASTELLANOS M., GARCIA-SOLACO M. Suitability of data models as canonical models for federated databases. SIGMOD RECORD 20(4), pages 44--48, 1991.

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F. Saltor, M. Castellanos, and M. Garc'ia-Solaco. Suitability of Data Models as Canonical Models for Federated DBs. ACM SIGMOD Record, 20(4), 1991.

....BarceLona Object Oriented Model (BLOOM for short) on an ObjectStore DBMS (DataBase Management System) BLOOM is a semantic extension of object oriented (O O) models, with a high degree of expressiveness. It was designed specifically to satisfy all desirable characteristics found in the analysis [SCGS91], both in expressiveness and in semantic relativism. That paper shows the needed characteristics of a data model to be used as Canonical Data Model (CDM) of a federation of databases. The BLOOM model is similar to other O O models. However, since it is an enrichment, it has things others do not ....

F. Saltor, M. Castellanos, and M. Garcia-Solaco. Suitability of data models as canonical models for federated databases. SIGMOD Record (ACM Special Interest Group on Management of Data), 20(4):44--48, December 1991.

....it explicit by converting the local schemas to rich component schemas expressed in our BLOOM canonical model. This model, briefly described in section 3, has been developed for the interoperability context and complies with all the characteristics of suitability of canonical models reported in [13]. Once the local schemas have been converted to BLOOM, they are analyzed in the detection phase. Typically, the detection of similarities among classes involves a very complex comparison task where each object in one database is compared with each object in another database, and these comparisons ....

....for synonym that are registered in a data dictionary. 3: The BLOOM model The choice of the canonical model used for the federated database system is critical in the process of schema integration. It must comply with several characteristics of expressiveness and semantic relativism reported in [13] that make it adequate for this process. In particular it must be rich enough to model the semantics already expressed in the local schemas, as well, as the semantics obtained from a semantic enrichment process to upgrade the semantic level of the schemas (section 4) so that similarities among ....

F.Saltor, M.G.Castellanos & M.Garca-Solaco: "Suitability of Data Models as Canonical Models for Federated Databases". ACM SIGMOD Record, Vol.20, No.4, Dec. 1991.

....[Fir97] TP98] Leaving aside the importance of performance, and paying special attention to conceptual design, in [AOSS00] we proposed a seven layers conceptual schemas architecture to integrate the DW in a federation of databases. It allowed us to see everything in a different context. Since [SCGS91] found O O models as good Canonical Data Models for a federation (from a semantical point of view) we suggested the usage of a multidimensional O O model to conceptually design the DMs. In next sections, we go further discussing the advantages of using the O O paradigm in multidimensional ....

....Caller Called, Derivability, and Dynamicity) are presented, and their usage in multidimensional modeling, one by one, is exemplified; the paper ends with some conclusions, acknowledgements, and references. 2 Benefits by O O Dimension Expressiveness or Semantic Power , as it is defined in [SCGS91], is the degree to which a model can express or represent a conception of the real world. It measures the power of the structures of the model to represent conceptual structures, and to be interpreted as such conceptual structures. The most expressive a model is, the better it represents the real ....

[Article contains additional citation context not shown here]

F. Saltor, M. Castellanos, and M. Garc'ia-Solaco. Suitability of Data Models as Canonical Models for Federated DBs. ACM SIGMOD Record, 20(4):44-- 48, 1991.

....the data all together. Thus, its strength does not have to be in easy querying, but in good integration and data semantics representation. Precisely because of that, we propose the CDM of the federation as a basis for a good data model for the DW. Object Oriented models were found as good CDM in [SCGS91], thereby we are arguing to have an object oriented model as CDM for the DW. Moreover, the importance of the time dimension in analysis tasks, as well as in the DW (notice the presence of the words time variant in its definition) suggests to use a temporal model. The process to obtain the DW ....

F. Saltor, M. Castellanos, and M. Garc'ia-Solaco. Suitability of Data Models as Canonical Models for Federated DBs. ACM SIGMOD Record, 20(4):44-- 48, 1991.

....the data all together. Thus, its strength does not have to be in easy querying, but in good integration and data semantics representation. Precisely because of that, we propose the CDM of the federation as a basis for a good data model for the DW. Object Oriented models were found as good CDM in [SCGS91] thereby we are arguing to have an object oriented model as CDM for the DW. Moreover, the importance of the time dimension in analysis tasks, as well as in the DW (notice the presence of the words time variant in its definition) suggests to temporally extend the model. The process to obtain ....

F. Saltor, M. Castellanos, and M. Garc'ia-Solaco. Suitability of Data Models as Canonical Models for Federated DBs. ACM SIGMOD Record, 20(4):44--48, 1991. 10

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F. Saltor, M. Castellanos, and M. Garca-Solaco. Suitability of data models as canonical models for federated databases. SIGMOD Record, 20(4):45--48, 1991.

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Felix Saltor, Malu Castellanos, and Manolo Garca-Solaco. Suitability of Data Models as Canonical Models for Federated DBs. ACM SIGMOD Record, 20(4):44-48, 1991.

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F.Saltor, M.Castellanos, M.Garcia-Solaco: `Suitability of Data Models as Canonical Models for Federated Databases ', SIGMOD RECORD, Vol. 20, No. 4, December 1991.

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