A Unified Approach to Structured, Semistructured and Unstructured Data

At the present time, the way in which we manage data depends on its structural features. In this report we propose a logical model and algebra which represents a step further in the process of bridging the gap between different data modeling approaches. In particular, the focus is on structured and semistructured data. Our model is based on set theory, as in the relational context, and on data graphs, logical data structures which are simple, mathematically defined, and very expressive. Our approach is parametric and flexible enough to adapt to heterogeneous application contexts, by simply tuning its parameters. The algebra is composed of a small and expressive set of operators. It deals with large collections of data instances, and it is orthogonal to the language used to internally manipulate them. In this way, we clearly distinguish between two levels of data manipulation: the internal one, for navigation and modification of data graphs, and the external one, for manipulation of sets of instances. 1. Department of Computer Science, University of Bologna, Mura Anteo Zamboni 7, 40127 Bologna, Italy 2. Department of Mathematics and Informatics, University of Camerino, Via Madonna delle Carceri 9, 62032 Camerino MC, Italy

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