Laconic schema mappings: computing core universal solutions by means of SQL queries

Source: arXiv

ABSTRACT We present a new method for computing core universal solutions in data exchange settings specified by source-to-target dependencies, by means of SQL queries. Unlike previously known algorithms, which are recursive in nature, our method can be implemented directly on top of any DBMS. Our method is based on the new notion of a laconic schema mapping. A laconic schema mapping is a schema mapping for which the canonical universal solution is the core universal solution. We give a procedure by which every schema mapping specified by FO s-t tgds can be turned into a laconic schema mapping specified by FO s-t tgds that may refer to a linear order on the domain of the source instance. We show that our results are optimal, in the sense that the linear order is necessary and the method cannot be extended to schema mapping involving target constraints.

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    ABSTRACT: Schema mapping is becoming pervasive in all data transformation, exchange, and integration tasks. It brings to the surface the problem of differences and mismatches between heterogeneous formats and models, respectively, used in source and target databases to be mapped one to another. In this chapter, we start by describing the problem of schema mapping, its background, and technical implications. Then, we outline the early schema mapping systems, along with the new generation of schema mapping tools. Moving from the former to the latter entailed a dramatic change in the performance of mapping generation algorithms. Finally, we conclude the chapter by revisiting the query answering techniques allowed by the mappings, and by discussing useful applications and future and current developments of schema mapping tools.
    12/2010: pages 111-147;
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    Conference Paper: Core schema mappings.
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    ABSTRACT: Research has investigated mappings among data sources under two perspectives. On one side, there are studies of practical tools for schema mapping generation; these focus on algorithms to generate mappings based on visual specifications provided by users. On the other side, we have theoretical researches about data exchange. These study how to generate a solution - i.e., a target instance - given a set of mappings usually specified as tuple generating dependencies. However, despite the fact that the notion of a core of a data exchange solution has been formally identified as an optimal solution, there are yet no mapping systems that support core computations. In this paper we introduce several new algorithms that contribute to bridge the gap between the practice of mapping generation and the theory of data exchange. We show how, given a mapping scenario, it is possible to generate an executable script that computes core solutions for the corresponding data exchange problem. The algorithms have been implemented and tested using common runtime engines to show that they guarantee very good performances, orders of magnitudes better than those of known algorithms that compute the core as a post-processing step.
    Proceedings of the ACM SIGMOD International Conference on Management of Data, SIGMOD 2009, Providence, Rhode Island, USA, June 29 - July 2, 2009; 01/2009
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    ABSTRACT: The increasing demand of matching and mapping tasks in modern integration scenarios has led to a plethora of tools for facilitating these tasks. While the plethora made these tools available to a broader audience, it led to some form of confusion regarding the exact nature, goals, core functionalities, expected features, and basic capabilities of these tools. Above all, it made performance measurements of these systems and their distinction a difficult task. The need for design and development of comparison standards that will allow the evaluation of these tools is becoming apparent. These standards are particularly important to mapping and matching system users, since they allow them to evaluate the relative merits of the systems and take the right business decisions. They are also important to mapping system developers, since they offer a way of comparing the system against competitors, and motivating improvements and further development. Finally, they are important to researchers as they serve as illustrations of the existing system limitations, triggering further research in the area. In this work, we provide a generic overview of the existing efforts on benchmarking schema matching and mapping tasks. We offer a comprehensive description of the problem, list the basic comparison criteria and techniques, and provide a description of the main functionalities and characteristics of existing systems.
    12/2010: pages 253-291;

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