Re: the relational model of data objects *and* program objects
Date: Mon, 18 Apr 2005 17:54:24 +0200
Message-ID: <4263d82f$1_at_news.fhg.de>
erk schrieb:
> Alexandr Savinov wrote:
>
>>Having "One True Data Dictionary" means binding the whole system to
>
> one
>
>>layer - it is absolutism, i.e., precisely what should be avoided.
>
>
> Since when did this become comp.databases.politics.totalitatianism? I
> have only a vague idea what you mean by "absolutism" in the context of
> computer systems, but it seems like a desirable property, given that we
> have to define and then reason about them.
>
>
>>We need a layered system of dictionaries (if we are talking about >>dictionaries) where one layer defines a dictionary which is used in >>another layer and so on.
>
>
> Why do we need this?
>
>
>>Any one dictionary is not absolute and is based >>on some more fundamental layers (just like its functionality, data >>structure, relationships and all other things).
>
>
> So the lower layer is absolute? You seem to confuse "absolute" with
> "atomic," though I'm not quite sure what you're getting at.
I mean that it is not good idea to have anything centralized including data dictionary or some functionality if it is not a really small piece of data/function. The centralized approach could be called absolutism, monumentalism, totalitarism, centralism or whatever other term you like but the idea is that your system has a single center of the universe. Suppose that all requests to resolve computer names go to one DNS server. This solution is easier to implement, it is more reliable and efficient but... only untill you rich some size. After that you need to decentralize the system. The same situation is in any large system including data management systems. It is already the next question how it can be implemented. For example, can we currently define a relational model within an existing relational model? No we cannot. It is a defect. Can we include a relational model into an existing model? No we cannot. It is a defect. We do not have simply a model for that and most people do not need this because they are tought to create systems with one model where all tables exist in one space where they have equal rights. Thus when we start a new system we say: let us create a database and then create 10,000 tables in it. It is the same as to say: let's define a procedure considing of 10,000 lines of code. Of course, we have various technlogies and solutions for distributing data and functions but we do not have a theory for that. So we normally simply aggregate some available solution by using our own hand-made adapters and connectors.
alex
http://conceptoriented.com
Received on Mon Apr 18 2005 - 17:54:24 CEST