Re: Does Codd's view of a relational database differ from that ofDate&Darwin?[M.Gittens]
From: Jan Hidders <jan.hidders_at_REMOVETHIS.pandora.be>
Date: Sun, 03 Jul 2005 13:07:18 GMT
Message-ID: <aqRxe.136262$X86.7247910_at_phobos.telenet-ops.be>
>>VC wrote:
>>
>>>How is it different ? Is it not just a notation for trees (with a lot of
>>>other baggage admittedly) ?
>>
>>Yes, ordered, node-labeled trees, whereas the other two are more about
>>graphs.
>
> Sorry to state the trivial but a tree *is* a graph (a rooted tree is a DAG).
Date: Sun, 03 Jul 2005 13:07:18 GMT
Message-ID: <aqRxe.136262$X86.7247910_at_phobos.telenet-ops.be>
VC wrote:
> "Jan Hidders" <jan.hidders_at_REMOVETHIS.pandora.be> wrote in message > news:CwAxe.135730$_81.6969472_at_phobos.telenet-ops.be... >
>>VC wrote:
>>
>>>How is it different ? Is it not just a notation for trees (with a lot of
>>>other baggage admittedly) ?
>>
>>Yes, ordered, node-labeled trees, whereas the other two are more about
>>graphs.
>
> Sorry to state the trivial but a tree *is* a graph (a rooted tree is a DAG).
Of course, but not evere graph is a tree. So XML could at best be seen as a restricted version of the others, and restrictions can severly change the nature of data models. Besides, I said *ordered* trees, and, yes, that matters.
- Jan Hidders