Re: Nearest Common Ancestor Report (XDb1's $1000 Challenge)

On 18 May 2004 12:33:14 -0700, Neo wrote:

>> > > you seem to desire the possibility to enter untyped data
>> > All things in XDb1 are typed/classified.
>> But I didn't use the word "classified", I used the word "untyped".
>
>In XDb1's data model type, class and domain are the same thing. Even
>C.J. Date begins one of his chapters by saying "domain is essentially
>a data type".

Hi Neo,

Well, I'm not much of a theorist. Even though I'm reading and writing this from the .theory group (I don't subscribe to the other three this is posted in), I am more a hands-on kind of guy.

That's probably the reason why I came up with a working solution, whereas the theorists constrain themselved to hitting you on the head with a large club for calling SQL Server and Access "reasonably close implementations of the relational model". (Actually, for the Access part I' tempted to ask them if I can borrow their club for a while :-> )

From my practical, hands-on real-world background, I treat types, classes and domains as three different things. A class is a set of individual items, events or notions from the real world that have enough attributes in common to warrant treating them as individual items from one set. A domain is the complete collection of allowable values for an attribute of individual members of a class. I like to think of a datatype as a superset of many domains. The domain for all integers is the same as the datatype integer. The domain for attribute "age (in years)" of the class "employee" is a subset of the integer domain.

(snip rest of your message - it's basically a repetition of an earlier message and I can't find any point in it that I didn't already address in a previous post)

Best, Hugo

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