Re: Does Codd's view of a relational database differ from that ofDate&Darwin?[M.Gittens]
Date: Sun, 03 Jul 2005 12:49:42 GMT
Message-ID: <G9Rxe.136249$3T6.7274553_at_phobos.telenet-ops.be>
Marshall Spight wrote:
> Jan Hidders wrote:
>
>>Marshall Spight wrote:
>>
>>>I'm still wildly unclear as to what this all means, but
>>>I got a hint from the above line.
>>>
>>>Is the word "abstract" here being used in the same sense that
>>>is in Java? Meaning roughly: uninstantiable with parts of the
>>>definition to be filled in at a later time?
>>
>>No, not really. It has to do with the distinction between on the one
>>hand houses, people and countries and on the other hand strings, numbers
>>and booleans. The latter three can be denoted directly, the first three
>>only indirectly by denoting a certain combination of values associated
>>with them.
> > Hmmm. I guess I don't see the point. There are some things that > computers can operate on, and there are some things they can't. > Real world objects are outside the realm of the computer; it can > only operate on its model of these things.
Yes. So when you are describing your model (i.e. the ORM schema) it is rather important to establish for which things this is the case, and for which things it isn't. In the instance the lexical objects can be represented as themselves, and the non-lexical objects can be represented by opaque keys.
- Jan Hidders