Rafi Ahmed, Joseph Albert, William Kent, Mohammad Ketabchi, Ming-Chien Shan, "Automatic Importation of Relational Schemas in Pegasus", HPL-9213, Hewlett-Packard Laboratories, October 1992.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....a good loading system should organize data on disk so as to optimize the run time of the applications that will use it. Some systems partly address these issues but none cover them all. Also, previous research on the topic has been targeted towards specific source and target systems [Ora, Fa87, Aa93, INC93, Ont96, WN96, WJLG00] Furthermore, all bulk loading tools are black boxes that generate programs that cannot be easily customized yet are not always appropriate (because, e.g. they use too much memory or result in a bad physical organization) In this paper, we propose a general solution ....

J. Albert and al. Automatic importation of relational schemas in Pegasus. In Intl. workshop on Research Issues on Data Engineering: Interoperability in Multidatabase System, 1993.

....these systems have evolved vastly, an important problem arises: how manage all these data in an integrated form. It has been followed fundamentally two approaches within the area of integration of information systems: a) Structural Integration ( 1, 2, 3, 4, 5, 6, 7] b) Operational Integration ([8, 9, 10]) The integration method that is used in this paper follows the operational integration approach. The data reside in any place in our heterogeneous systems and a group of operations (or services) are provided to allow the management of this data. The other approach, called structural ....

J. Albert, R. Ahmed, M. Ketabchi, W. Kent, and M. Shan. Automatic importation of relational schemas in pegasus. In Proc. of the 3rd International Workshop on Research Issues in data Engineering: Interoperability in Multidatabase Systems. Vienna, Austria, pages 105--113, 1993.

....Discrepancies that may occur within the same data model is investigated by Krishnamurthy et al. . 1991) Kim and Seo (1991) provide an exhaustive list of conflicts that may occur in a multidatabase environment, expressed in the context of the relational data model. Ahmed et al. (1993) Albert et al. (1993) describe Pegasus, a heterogeneous DBMS that provides access to native and external heterogeneous (relational) schema. Here, too, queries can only access the local schema via the imported Pegasus global schema. Finally, in SIMS (see Arens and Knoblock (1992) information sharing from multiple ....

Albert, J., R. Ahmed, M. Ketabchi, W. Kent, M. Shan (1993) "Automatic importation of relational schemas in Pegasus," Proceedings of the International Conference on Data Engineering.

....data model is investigated by [Krishnamurthy et al. , 1991] Kim and Seo, 1991] provide an exhaustive list of conflicts that may occur in a multidatabase environment, expressed in the context of the relational data model. This is later extended to the object data model in [Kim et al. , 1993] In [Albert et al. , 1993], Pegasus, a heterogeneous DBMS that provides access to native and external heterogeneous (relational) schema is described. Here, too, queries can only access the local schema via the imported Pegasus global schema. In SIMS [Arens and Knoblock, 1992] information sharing from multiple relational ....

Albert, J., R. Ahmed, M. Ketabchi, W. Kent, M. Shan (1993) "Automatic importation of relational schemas in Pegasus," Proceedings of the International Conference on Data Engineering.

....such tools, the translation process produces not only the translated schema, but a set of correspondences between the schemas that defines how an instance of the former corresponds to an instance of the latter. We call these correspondences instance mappings. For example, the Pegasus import tool [2] translates relational schemas to Iris schemas (Iris is a functional object model) For each Iris type, the result of translation includes a rule over a collection of relations in the original schema that defines the instances of the type. Such translation tools fully automate the production of ....

J. Albert, R. Ahmed, M. A. Ketabchi, W. Kent, and M. C. Shan. Automatic Importation of Relational Schemas in Pegasus. In Proc. of the 3rd Int'l Workshop on Research Issues in Data Eng.: Interoperability in Multidatabase Systems, pages 105--113, Vienna, Austria, Apr. 1993.

....While some vendors offer import translators from a few common formats, in general these do not provide sufficient interoperability. It has been recognized that finding solutions to interoperability in a large network of databases is going to be a major research area in the next decade or so. [1] 2. Since an API is a set of functions to be accessed via remote or local procedure invocation, a relational API presents data in terms of named arrays (relation tables) that contain flat tuples, with one data value per column in each tuple, and with the number of columns fixed per named array. ....

....[8, 11] Seen from a higher level, what is needed are mediation services [22] among different representations and systems. Schema Integration: Database design tools have been applied to schema integration [17] and related work formalizes interdatabase dependencies [18] and schema merging [1, 6]. Related approaches utilize data migration [16] Some of the work in this area assumes that the resulting target schema or view is to be relational rather than another heterogeneous representation. Object Encapsulation: Since object technology can hide the implementation and data structures ....

Ahmed, R., Albert,J., Ketabchi,M., & Shan,M., Automatic Importation of Relational Schemas in Pegasus, Proc.3rd Int'l Workshop on Research Issues in Data Engineering: Interoperability in Multidatabase Systems, April 1993, Vienna, Austria, IEEE Press.

....interface by making the heterogeneity and distribution of information sources largely transparent. In addition, its construction does not disturb running applications (some of which might be mission critical applications) Many MDB projects have been reported in the literature, for example Pegasus [AHM91, ALB93, RAF91], Multibase [LAN82, SMI81] and Myriad 5 [CLE93, LIM94a] For a comprehensive list refer to [BUK96a] Pegasus [AHM91, ALB93, PIT96, RAF91] is a heterogeneous MDB system that supports interoperability between a wide range of information sources. Its canonical data model is based on the Iris OO ....

.... not disturb running applications (some of which might be mission critical applications) Many MDB projects have been reported in the literature, for example Pegasus [AHM91, ALB93, RAF91] Multibase [LAN82, SMI81] and Myriad 5 [CLE93, LIM94a] For a comprehensive list refer to [BUK96a] Pegasus [AHM91, ALB93, PIT96, RAF91] is a heterogeneous MDB system that supports interoperability between a wide range of information sources. Its canonical data model is based on the Iris OO data model [FIS87] Myriad [CLE93, LIM94a] by contrast, is a federated database prototype that was developed at the University of Minnesota. ....

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J. Albert et al. Automatic Importation of Relational Schemas in Pegasus. In Research Issues in Data Engineering: Interoperability in Multidatabase Systems (RIDE-IMS'93), pages 105--113, Vienna, Austria, 1993.

....of objects with identifiers from relational data using an inflationary fixpoint semantics. A similar approach can be found in [23] The idea of automatically derived class populations appeared first in the notion of virtual and imaginary classes [1] A similar idea has been used in the Pegasus [3, 15] system, based on an import mechanism. Pegasus translates a relational schema into an Iris [14] database schema. It provides mapping facilities for generating imported schema but also translates Pegasus queries into the data manipulation languages of the external databases. More recently, gateways ....

J. Albert et al. Automatic importation of relational schemas in Pegasus. In Proc. RIDE-IMS'93, 1993.

....schema (typically in a different data model) which can be used as a view to pose queries on data stored under the original schema. Within such tools, the translation process produces not only the translated schema, but an instance mapping between the schemas. For example, the Pegasus import tool [2] translates relational schemas to Iris schemas (Iris is a functional object model) For each Iris type, the result of translation includes a rule over a collection of relations in the original schema that defines the instances of the type. Such translation tools fully automate the production of ....

J. Albert, R. Ahmed, M. A. Ketabchi, W. Kent, and M. C. Shan. Automatic Importation of Relational Schemas in Pegasus. In Proc. of the 3rd Int'l Workshop on Research Issues in Data Eng.: Interoperability in Multidatabase Systems, pp. 105--113, Vienna, Austria, Apr. 1993.

....methodology based on a classification of the relations according to the existence of primary key attributes in the left hand side of inclusion dependencies. Some approaches take into account more forms of relational constraints [5] 11] in particular candidate key based inclusion dependencies. [2] offers a technique for automatically importing relational schema into a functional object model. However, they suppose that the relational schema contain primary keys and referential integrity constraints. The most complete method seems to be [6] the innovation is the exhaustive taxonomy used to ....

Albert J., Ahmed R., Ketchabi M., Kent W., Shan M.C., "Automatic Importation of Relational Schemas in Pegasus", Proceedings of the third Int. Workshop on Research Issues in Data Engineering, pp 105113, Vienna, 1993.

....powerful data model has a.o. been conducted by Saltor and Castellanos. 4] contains a quite exhaustive treatment which uses the object oriented data model BLOOM as its target model. The Pegasus project at Hewlett Packard Laboratories uses a functional object model as its common data model. [1] describes the translation method used for relational schemata. The latter approach requires less semantic input, resulting in an output schema that bears more resemblance to the original relational schema; for example, so called missing entities are not identified. Translation of a relational ....

J. Albert, R. Ahmed, M. Ketabchi, W. Kent & M-C. Shan, "Automatic importation of relational schemas in Pegasus," in RIDE Interoperability in Multidatabase Systems, IEEE Computer Society Press, Los Alamitos, CA, 1993, 105--113.

....different schema (F logic schema) where the semantics may not be equivalent. Many approaches advocate support of a global schema and several systems have been proposed and built as a result of this research, e.g. Multibase (see Dayal and Hwang (1984) Pegasus (see Ahmed et al. (1991, 1993) Albert et al. (1993)) UniSQL M (see Kim et al.(1993) Kim and Seo (1991) and SIMS (see (Arens and Knoblock (1992) Arens et al.(1993) Hsu and Knoblock (1993) One shortcoming of building a unified global schema is that all queries must be posed against this schema. Such an approach cannot provide interoperability ....

....relational schema, and it could be an attribute name or a relation name in another schema. In later research, such heterogeneity was also considered and resolved. Several systems have been proposed and or built, e.g. Multibase (see Dayal and Hwang (1984) Pegasus (see Ahmed et al. (1991, 1993) Albert et al. (1993)) UniSQL M (see Kim et al.(1993) Kim and Seo (1991) and SIMS (see (Arens and Knoblock (1992) Arens et al.(1993) Hsu and Knoblock (1993) In the global schema approach, a single unified global schema is created such that each external or remote database is a model of that schema, i.e. the ....

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Albert, J., Ahmed, R., Ketabchi, M., Kent, W. and Shan, M.-C. (1993) "Automatic importation of relational schemas in Pegasus," Proceedings of the Workshop on Research Issues in Data Engineering, International Conference on Data Engineering.

....and Gangopadhyay (1992) Krishnamurthy et al. (1991) Lakshmanan (1993) and are not well supported under current DBMS technology. There have been a few systems that have studied query processing and or have been implemented, e.g. Multibase [Dayal and Hwang (1984) Pegasus [Ahmed et al. (1991) Albert et al. (1993)] UniSQL M [Kim et al. (1993) Kim and Seo (1992) SIMS [Arens and Knoblock (1992) Arens et al. (1993) Alternative approaches either specify a canonical mediator knowledge base which has mapping knowledge among different schema [Chang et al. (1994) Qian (1993) Qian and Raschid (1995) ....

....language. For example, HOSQL in the case of Pegasus and SQL M in the case of UniSQL M. There has been some research in query optimization and query decomposition in heterogeneous environments in the Pegasus, SIMS and UniSQL M projects. For example, the Pegasus project [Ahmed et al. (1991) Albert et al. (1993)] studies both query reformulation as well as query optimization. During query processing, the HOSQL query is represented as an E tree (of sub queries and operations) in some extended relational algebra. If there are multiple external sources for the data (EDRM) then appropriate translations ....

Albert, J., Ahmed, R., Ketabchi, M., Kent, W. and Shan, M.-C. (1993) "Automatic importation of relational schemas in Pegasus," Proc. of the Workshop on Research Issues in Data Engineering, ICDE-93.

....are created to resolve and homogenize heterogeneous entities in both relational and object oriented schemas. They provide several unified operators including a vertical join operator (similar to a tuple constructor) and a horizontal join operator (similar to a union operation) Ahm93] and [Alb93] describe Pegasus, a heterogeneous DBMS that provides access to native and external heterogeneous schemas. Queries access the local schema via the imported Pegasus global schema. In Pegasus, HOSQL, a higher order functional language defines the imported types (corresponding to class definitions) ....

Albert, J., R. Ahmed, M. Ketabchi, W. Kent, M. Shan "Automatic importation of relational schemas in Pegasus," Proceedings of the International Conference on Data Engineering, 1993.

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Rafi Ahmed, Joseph Albert, William Kent, Mohammad Ketabchi, Ming-Chien Shan, "Automatic Importation of Relational Schemas in Pegasus", HPL-9213, Hewlett-Packard Laboratories, October 1992.

....stored data in either UDM. All UDM schema objects are derived, and mapping facilities are provided to define derived constructs. In this paper, the MOOSE UDM consists of those features of the MOOSE data model that are known to be needed to represent relational schemas as object oriented schemas [2]. Specifically, the MOOSE UDM consists of the structural part of a typical object oriented data model. Thus, the results described here would be applicable if a different object oriented data model were used for the object oriented UDM. The relational UDM supports relations with attributes having ....

....to effect the translation, and the MOOSE schema is generated automatically, including the CORAL rules that are needed to define the virtual instances of the type in the MOOSE schema. The method used in RODIN to map relational schemas to object oriented schemas is derived from known techniques [2, 19, 34]. The salient technique is an algorithm that analyzes dependency information (primary keys, foreign keys, and key inclusion dependencies) and generates automatically an object oriented schema that represents the same data semantics. The object oriented schema generated by this algorithm is ....

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J. Albert, R. Ahmed, M. Ketabchi, W. Kent, and M.-C. Shan. Automatic importation of relational schemas in Pegasus. In Proc. of the Int'l Workshop on Research Issues in Data Engineering - Interoperability in Multidatabase Systems,Vienna, Apr. 1993.

....expressed somewhere. 8 4.3.2 Import Suppose we are accessing information about students, teachers, and courses from various universities. One of the university sources might export a relational schema as shown in Figure 3. Type relationships can be inferred from certain inclusion dependencies [3] (indicated as in Figure 3) Simple key inclusions imply subtypes, so the Teacher type is imported as a subtype of Person. Mutual key inclusions imply vertical partitioning, so StudentHealth and StudentAcad are recognized as providing data about the same objects, and hence are imported as a ....

....A plausible implementation strategy would be to construct an object identifier as a concatenation of a producer value with a unique tag associated with each imported type. The disjointness assumption can be relaxed, for example, if inclusion dependencies are known for a relational data source [3]. The disjointness assumption is clearly inapplicable in the case of vertical partitioning, since the underlying relations are imported into a single type. The assumption is also inappropriate for subtypes, as indicated by key inclusion dependencies. It does not make sense to treat Teacher or ....

Joseph Albert, Rafi Ahmed, Mohammad Ketabchi, William Kent, Ming-Chien Shan, "Automatic Importation of Relational Schemas in Pegasus", Proc. RIDE-IMS, April 1920

.... [16, 8, 17] 20 Object Oriented Databases [12, 11] 27 Object Relational Databases [14, 18] Feb 3 Deductive Databases and Recursion [10, 1] Project status report due in class 10 Deductive Databases and Recursion [5, 13] 17 Introduction to Heterogeneous Multidatabases [15] Data Model Translation [3] 24 Data Integration [9, 6, 2] Mar 3 Topics in Relational Database Theory [7, 4] 10 Additional topic time permitting, students choice Project due in class 17 Final in class ....

Albert, J., et al. Automatic importation of relational schemas in Pegasus. In Proc. of the Int'l Workshop on Research Issues in Data Engineering - Interoperability in Multidatabase Systems (Vienna, Apr. 1993).

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Albert, J., R. Ahmed, M. Ketabchi, W. Kent, M. Shan (1993) "Automatic importation of relational schemas in Pegasus," Proceedings of the International Conference on Data Engineering.

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Albert J., Ahmed R., Rafi A., Ketabchi M., Kent W.,Shan M., "Automatic Importation of Relational Schemas in Pegasus", in Proceedings of the 3rd International Workshop on RIDEIMS, Vienna, Austria , april 1993.

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J. Albert, R. Ahmed, M. Ketabchi, W. Kent, and M. Shan. Automatic importation of relational schemas in pegasus. In 3rd International workshop on research issues on data engineering: interoperability in multidatabase systems, 1993.

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