U. Dayal and H. Hwang. View definition and generalisation for database integration in multibase: A system for heterogeneous distributed databases. IEEE Transactions on Software Engineering, 10(6):628--644, November 1984.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....and integration, is programmed in JAVA. YAT is now being used within the OPAL European Project that is concerned with Intranet tools for the manufacturing industry. An on line demonstration of the YAT system is also available 2 . There exist several data conversion integration languages (e.g. DH84, AH88, Kos96, ACM97, PGMU96, PAGM96] as well as many query languages for semi structured data offering similar capabilities (e.g. Abi97, BDHS96, AQM 97] However, query languages are not well suited to describe data conversions, that require richer restructuring capabilities. Some ....

....well as many query languages for semi structured data offering similar capabilities (e.g. Abi97, BDHS96, AQM 97] However, query languages are not well suited to describe data conversions, that require richer restructuring capabilities. Some proposals focusing on database translations like [DH84, AH88, Kos96, DK97] give an answer to this problem but follows a schema driven approach which misses flexibility. Finally, PGMU96, PAGM96] is the closest related work, but the proposed language cannot address recursive translations and ordered collections. In any case, no approach so far offers ....

U. Dayal and H. Hwang. View definition and generalisation for database integration in multibase: A system for heterogeneous distributed databases. IEEE Transactions on Software Engineering, 10(6):628--644, November 1984.

....in advance to detect inter schema correspondences and conflicts. After that, a homogeneous global schema is created for end users by integrating all the local concepts into composite global ones. This integration process includes reconciling the conflicts discovered during the analysis phase [COL91, DAY84, DOG95, HAY90, MOT83, MOT87, QUT92, QUT93, NAV96a]. Alternatively in this approach, several tailored global schemas may be defined instead of one global schema [BER91, CLE93, FAH94, 5 LIM94a, ZHA91] This has the advantages of supporting customisability, potentially reducing the size of the global schema as seen by users, minimising the ....

....this type of MDB system is that users are protected from the effects of heterogeneity by the provision of a consistent and non redundant global representation(s) Tightly coupled federations can be further subdivided into single federation and multiple federations. A single federation MDB system [COL91, DAY84, DOG95, 28 HAY90, MOT83, MOT87, QUT92, QUT93, SPA92] (see figure 2.4) allows the creation and management of only one federated schema or global schema. This federated schema is a consistent, non redundant and complete representation of all the local information [BAT86] This helps in maintaining uniformity in semantic interpretation of the ....

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U. Dayal and H. Hwang. View Definition and Generalisation for Database Integration in a Multidatabase System. IEEE Transactions on Software Engineering, SE-10(6), pages 628--645, 1984.

....and integration, is implemented in JAVA. YAT is now being used within the OPAL European Project that is concerned with Intranet tools for the manufacturing industry. An on line demonstration of the YAT system is also available 2 . There exist several conversion or integration languages (e.g. [15, 16, 17, 11, 18, 13]) as well as many query languages for semistructured data, offering similar capabilities [19, 6, 7] However, query languages are not well suited to describe data conversions, that require richer restructuring capabilities. Some proposals focusing on database translations like [15, 16, 17, 20] ....

....16, 17, 11, 18, 13] as well as many query languages for semistructured data, offering similar capabilities [19, 6, 7] However, query languages are not well suited to describe data conversions, that require richer restructuring capabilities. Some proposals focusing on database translations like [15, 16, 17, 20] give an answer to this problem but follows a schema driven approach which misses flexibility. Finally, 18, 13] is the closest related work, but the proposed language cannot address recursive translations and ordered collections. In any case, no approach so far offers the ability to deal in an ....

U. Dayal and H. Hwang, "View definition and generalisation for database integration in multibase: A system for heterogeneous distributed databases," IEEE Transactions on Software Engineering, vol. 10, no. 6, pp. 628--644, Nov. 1984.

....to implement an instantiated implementation but not vice versa. Thus a methodology for tightly integrated views is extremely flexible. Much of the research within the database community has been to develop methodologies for performing one or more of the integration tasks. For example, Multibase [11] is a methodology for implementing view integrations, and suggests a limited family of schema transformations for integrating schemas. The underlying model is functional, and the query language is Daplex. A solution using Multibase could range from fairly loose to very tight integration, but ....

....limited family of schema transformations for integrating schemas. The underlying model is functional, and the query language is Daplex. A solution using Multibase could range from fairly loose to very tight integration, but always a view implementation. Furthermore, since there is no discussion in [11] of the first step of integration, translation from a given model into the functional model, it is immediately applicable only for functional databases which support Daplex. The federated architecture suggested in [14] and later in [18] is a methodology which always yields a loosely federated ....

Dayal, U., and Hwang, H. View definition and generalisation for database integration in Multibase: A system for heterogeneous distributed databases. IEEE Transactions on Software Engineering SE--10, 6 (November 1984), 628--644.

....be reflected on the underlying data: we could insert a default value for the attribute wherever it is omitted, or we could simply delete any objects from the class for which the attribute value is missing. An alternative approach is to use some high level language to describe transformations as in [3, 9]. In such an approach, the effect of a transformation on the underlying data becomes explicit. We use the term database transformation, as opposed to the more common term schema transformation, to emphasize this distinction. A database transformation language should be sufficiently expressive to ....

U. Dayal and H. Hwang. View definition and generalisation for database integration in Multibase: A system for heterogeneous distributed databases. IEEE Transactions on Software Engineering, SE--10(6):628--644, November 1984.

....able to consider an instance of p to be an instance of q, p must at least have all the arrows of q, and these arrows must have classes for which every instance can be considered to be an instance of class of the corresponding arrow of q. The conditions A1 and A2 are equivalent to those given in [6] and also in [7] for functional schemas (though the former incorporated specialisation relations between arrows, while the later used unlabelled arrows) oe ae oe ae oe ae oe ae 6 6 H H H H Hj Phi Phi Phi Phi Phi XXX Xz : id num:int age:int name:str owner:str ....

....of as meta schemas which the schemas must satisfy. In [3] we define a representation for such meta schemas and use them to show that the merging process described in Section 3 respects such restrictions. In an unconstrained form, our schemas are similar to those of the functional data model ([6, 8]) though they are not sophisticated enough to interpret data models such as those proposed in [1] or [9] which incorporate constructors for variants. As we develop our data model, we will incorporate the idea of object identity, thus making it suitable for modeling the object oriented databases ....

U. Dayal and H. Hwang. View definition and generalisation for database integration in multibase. IEEE Transactions on Software Engineering, SE--10(6):628-- 644, November 1984.

....the source databases. The first of these approaches can be thought of as performing a one time bulk transformation, while the second approach evaluates transformations in a call by need manner. For example, the most common approach adopted within federated database systems [14] is call by need [25,10,22]. This approach has the advantage that the source databases retain their autonomy, and updates to the various source databases are automatically reflected in the target database. However, in cases where accessing the component databases is costly and the databases are not frequently updated, ....

....tool. There are two basic approaches to systems for implementing transformations to resolve such structural conflicts: using a small set of simple transformations or heuristics that can be applied in series [25,5,24,32] or using some high level language to describe the transformation [1,10]. Examples of such approaches will be given in section 2.3. The advantage of using a small set of pre defined atomic transformations is that they are simple to reason about and prove correctness for. For instance, one could prove that each transformation was information preserving [29,24] or if ....

U. Dayal and H. Hwang. View definition and generalisation for database integration in Multibase: A system for heterogeneous distributed databases. IEEE Transactions on Software Engineering, SE--10(6):628--644, November 1984.

....For example, none of the systems mentioned would be able to deal with the transformation between the Boolean is capital attribute of Cites and the capital attribute Countries in the example above. An alternative approach is to use some high level language to describe the transformations as in [1, 8]. The problem here is to find a language which is declarative and easy to specify transformations in, but is sufficiently expressive to deal with all the transformations and data structures likely to arise, and can be implemented in an efficient manner. The rewrite rules of [1] are the closest ....

U. Dayal and H. Hwang. View definition and generalisation for database integration in Multibase: A system for heterogeneous distributed databases. IEEE Transactions on Software Engineering, SE--10(6):628--644, November 1984.

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