Re: dbdebunk 'Quote of Week' comment


"Alexandr Savinov" <spam@xxxxxxxxxxxxxxxxxxx> wrote in message
news:4312e49d$1@xxxxxxxxxxxxxx


> You have only one serious flaw in your reasoning:
>
> we need an element in our model that will denote an end-user

> In this sense I find your approach to defining meaningfulness rather
> useful but unfortunately I do not know a formal theory that could deal
> with end-users as an integral part of the model. We can dras boxes,
> arrows, circles but it will not be a formal model.

But we have the three level architecture of DBMSs.
About formal models, I don't know either but I found this
http://people.cs.vt.edu/~jaburge/abstract.html .

> In general I think that we lack information on "identtity modeling"
> althoug it is as important as data modeling itself. Identity modeling is
> a separate topic, a dual part for data modeling. In other words, we can
> model identity ignoring object properties. And it may well be rather
> complex model. It will involve entities without properties - only
> identities. The following properties of identity make this task rather
> difficult:
>
> - Identity is distributed among many entites. It can be hierarchical.
> For example, an element of categorization might have several segments
> each specifying relative position. A fully qualified identifier then is
> composed of several identifiers (for example, several primary keys taken
> from different tables - having one primary key is not enough).
>
> - Identity cannot be considered without its scope. For example, a
> physical address is retricted by the scope of one computer, a primary
> key might be restricted by one database etc.
>
> - Logical/physical is a relative characterization rather than absolute.
> Memory handle is really physical for an application program that uses
> it, but it is logical for operating system w.r.t. to absolute offsets
> in physical memory (offset may change while memory handle does not
> change). In this sense all those disputes about lgoical/physical are
> meaningless without specifying the context. Primary key may well be
> viewed as a physical identifier from the point of view of some higher
> level identification mechanism, say, global id. This means that global
> id is permanent while primary key it substitues may change.
>
> - Any identifier is based on some environemnt that provides a coordinate
> system that it uses to produce its own identifiers. In other words, any
> new identification system is based on some lower level identification
> system (environemtn or context) with its scope and structure.

Thank you for this list.



.

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