Constructivity and Computability in Historical and Philosophical Perspective by Jacques Dubucs & Michel Bourdeau

Author:Jacques Dubucs & Michel Bourdeau
Language: eng
Format: epub
Publisher: Springer Netherlands, Dordrecht

4.4.3 Database and Bottom-Up Versus Top-Down Duality

Let us now look at the elaboration and use of databases in the perspective of bottom-up and top-down approaches. It turns out that this is much the same as with keywords and Google queries. 1.The choice of the relational schema is done using a bottom-up or top-down operational mode. In general, both modes are used jointly (in fact, alternatively). In the bottom-up mode, one uses the expected future content of the database to build its relational schema (which will structure this content). In the top-down mode one builds the relational schema on considerations which are external to the future content. At first glance, using the bottom-up operational mode may seem paradoxical: to use the content in order to structure it. But this is not the case. In practice, to build a relational schema for a given database, one starts from some sketchy idea of the schema, represents it as some graphic (top-down approach), then implements it (this is programming work). A kind of prototype is thus obtained. This being done, one fills the tables of the database with a few lines (a “set of data”) to test the pertinence of the relational schema, which may lead to adjust it (bottom-up approach). And this may be repeated… Recall that the content of a database is precisely what gives the semantics of the database whereas the construction of the relational schema is morphology (syntax). With such a mix approach, one can build the morphological (syntactic) part of the database via some access to a part of the semantics of the database. And vice-versa. Thus, this approach, so seemingly paradoxical, is not so. In fact, there are two true difficulties. First, to delimit the scope of the information system which is to be modeled, and this is done using the given specifications. Second, to choose the right level of abstraction of each component (attributes, tables, etc.).

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