Re: some ideas about db rheory
Date: Fri, 31 Jul 2009 04:39:47 -0700 (PDT)
On 20 srp, 23:09, rp_at_raampje.(none) (Reinier Post) wrote:
> I am afraid I do not see the difference.
> I wrote that reply to ask you what the difference is.
Given that I have spent much time working on this paper, constructive criticism is always welcome. Your comments, however, are more often intended as degrading than constructive. So I will reply on a lighter note.
> Second, it seems to me that your use of identifiers
> can be eliminated systematically and *losslessly*, i.e. without
> diminishing expressive power. I'm curious whether this is the case.
No this is not the case, I will give you two examples:
Example1. You need to make a db for a car dealer , who sells new Honda Civic vehicles. All of these vehicles are identical. If you eliminate the identifier, that is the VIN (vehicle identification number) it will be impossible to make a db (in the RM) for this dealer.
Example2. If you eliminate identifiers from any database, I suggest
the following algorithm:
Case1 - The key has less than 100 attributes.
If the server looks like Christmas tree, that is, if all the lamps are blinking,
feel free to continue to do what you have been doing. Case2 - The key has between 100 and 200 attributes.
If you notice smoke caming from server, consider calling
Case3 - The key has more than 200 attributes.
Now buy a candle, because the fuse on the nearest power plant will blow.
Note that there have been cases in this user group with relations that have 200+ attributes.
In real life 99 procent of business applications use identifiers. This happenms because IT professionals are ahead of IT theoretics. In my paper, you can find a theoretical background for identifiers.
> You represent these 'meta-data' in a separate table and then link them
> to the 'concept' using an identifier attribute.
Since I have not mentioned the terms meta-data or table in my paper, please do not use them as mine, and then criticize me about them. I do not think that time or people are meta-data. It would do our discussion good if you gave us a drfinition for meta-data and data. Otherwise, I will not take you seriously. ( You can find a definition of data in my paper).
> I don't understand. Suppose your database has an entity Person.
> I am a person. What is my identifier?
You can try to follow your ideas and use your attributes strictly for your identification and representation.
Vladimir Odrljin Received on Fri Jul 31 2009 - 13:39:47 CEST