Re: Database design

mAsterdam schrieb:
> Mark Johnson wrote:

>> .... For all intents, a component or concept
>> can itself become a leaf or black box. An atom or unit. An item. 

The main problem of existing theories here is that it is not possible to explain atomic/non-atomic distinction using only _one_ membership relation. In other words, the approach where we say that "something with no other elements inside is said to be atomic" works badly - we are not able to explain many interesting phenomena (particularly, in data modeling). From mathematical point of view this means that having only the classical set is not enough - we need something else. Sets do not explain many interesting things we observe.

One solution to that consists in using _two_ containment relations which have a fundamental nature. So a thing can be atomic in one structure and non-atomic in another structure and vice versa. For example, here are two ways to model a simple organizational structure:

• A table with the name of organization has records which are concrete departments within this organization (physical containment).
• one table ORGANIZATIONS contains records which are concrete organizations while a table DEPARTMENTS contains records which are concrete departments with a field pointing to their organization.

In both cases a department belongs to an organization but we model it using two (and only two) different structures.

>> And
>> any item can be a component, and has some limited meaning and utility
>> by itself, by its very definition. The tone middle-C is still
>> middle-C. In the same example, I can see, however, that one might wish
>> to distinguish such elementary building blocks as a controller scalar
>> from a full run of such. Still, I don't know. I suppose as a practical
>> matter, one would only reference a component but have to refer to
>> items in a different fashion.

It is convenient to view things within the second structure as entities while the things within the first structure would be viewed as identities (or maybe more correct is identifiers).

-- 
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