Assumptions in relational database theory

Many results in relational database theory on the structure of dependencies, query languages, and databases in general have now been established. Database software for mac However, neither (a) the reliance of these results on various assumptions, nor (b) the desirability or reasonableness of these assumptions themselves have been closely examined. Database questions for interview These assumptions are nontrivial: examples include the universal relation assumption and the lossless join assumption.The purpose of the present paper is to clarify many of the existing assumptions, and point out weaknesses. Database cleaner This is desirable both to harden the statements of previous results, and to evaluate recent suggestions that certain assumptions (such as the acyclic JD assumption) may be useful for modeling “real world” databases. Data recovery hard disk Specifically, studies are made of assumptions made for (1) universal relations, (2) functional dependency inference, and (3) decomposition theory. Data recovery jakarta We show that:• Some assumptions (such as uniqueness of relationships among attributes) can be more powerful than they appear;• common treatment of FDs is sometimes inappropriate, and for example FD inferences such as {A → B, B → C} |= A → C can be incorrect;• the ‘decomposition’ approach to design may be hard to justify in real terms; and• Acyclic JDs may have drawbacks in eliminating ambiguity in queries and in modeling real enterprises.It is hoped that this exposition will help clarify some confusing issues in this field, and will lead to a better understanding of which assumptions are reasonable and useful in modeling the “real world”.

[Show abstract] [Hide abstract] ABSTRACT: With an impressive theoretical foundation, normalization was supposed to bring rigor and relevance into such a slippery domain as database design is. 7 data recovery suite registration code Almost every database textbook treats normalization in a certain extent, usually suggesting that the topic is so clear and consolidated that it does not deserve deeper discussions. Data recovery raw But the reality is completely different.


Database library After more than three decades, normalization not only has lost much of its interest in the research papers, but also is still looking for practitioners to apply it effectively. Data recovery ssd Despite the vast amount of database literature, comprehensive books illustrating the application of normalization to effective real-world applications are still waited. Data recovery on iphone This paper reflects the point of view of an Information Systems academic who incidentally has been for almost twenty years a practitioner in developing database applications. A data recovery tool It outlines the main weaknesses of normalization and offers some explanations about the failure of a generous framework in becoming the so much needed universal guide for database designers. Data recovery expert Practitioners might be interested in finding out (or confirming) some of the normalization misformulations, misinterpretations, inconsistencies and fallacies. Data recovery jobs Theorists could find useful the presentation of some issues where the normalization theory was proved to be inadequate, not relevant, or source of confusion.

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