Re: How to model searchable properties of an entity

"Rene Hartmann" <rehartmann_at_t-online.de> wrote in message news:Pine.LNX.4.33.0408172050260.1642-100000_at_linux.local...
> I am also wondering why many people feel so unformfortable about
> having may tables. For most OO people, it is quite natural to have
> many classes, and to have "complex objects" which consist of many
> "sub-objects". But when it's about a relational model of the data, they
> say: "Oh look, how complex and clumsy this is - the data is spread over so
> many tables!"

I think there are many reasons. But the one that strikes me as the deepest one is that
object oriented and data centric people have a fundamentally different way of thinking about
abstraction.

Abstraction, in general, is the deliberate omission from consideration of certain details, that are seen as immaterial to the matter at hand. Basically, the human mind can't cope with "reality" unless some details are omitted.

There is a special form of abstraction in the OO world called, "encapsulation". Most readers will already know what encapsulation is, so I won't try to define it. But basically, "encapsulation" facilitates abstraction by hiding information that ought to be hidden, for some reason. If that information changes later on, the consequenses are contained precisely because the information was hidden.

Data Centric people (like myself) go for a different special form of abstraction called "data independence". Basically a query's results (and to some extent it's performance) should not depend on features of the data unused by the query. Thus, if a query pulls last names, first names, and phone numbers out of a database, it should work the same if someone comes along and changes all the zip codes from 5 digits to 9 digits.

Encapsulation and Data Independence both protect systems from what has been called "the ripple effect". (You throw a rock in the middle of a pond, and pretty soon, there are ripples all over the surface. ) But they do so in such radically different ways that each of them looks counterproductive, if not downright dangerous, to the other camp. Received on Tue Aug 17 2004 - 22:22:50 CEST