Re: Canonical DB

From: mAsterdam <>
Date: Fri, 23 Jun 2006 16:48:45 +0200
Message-ID: <449bfec1$0$31656$>

Dmitry A. Kazakov wrote:
> mAsterdam wrote:

>>Googling for 'graphs RM' gives
>>;-), substituting 'relational' for 'RM' made me stumble on

> I'm not sure that the latter is really "relational" in the sense of RM. The
> algebra of the relations between matched instances of pattern atoms is not
> necessary RA. [That's all I can derive from the text, I might be wrong.]
> The approach itself is common for text pattern matching, as well.

The sentence "In the relational paradigm, patterns are formed not only by the nature of the objects which make the pattern, but also by their relationships to each other." is suspect (to put it mildly).

Both these links just happened to be the one on top in the Google search anyone interested in the answer to "Uh... So in RM there just *aren't* graphs or trees? " could have done. Below are some I happen to know which may be somewhat more difficult to find.

>>If you don't mind getting your hands dirty:
>> mentions
>>some Oracle specifics, in 
>>Vadim Tropashko discusses two ways "to model a tree
>>in the database". His new book might be on the way
>>to the stores by now, but I did not find a reference.
>>Joe Celko wrote 

> Reading such things one should always ask himself: what was lost?

And: what was added?

> Any tree built in any way is a tree.
> Once you have it, it will not fully obey RA or
> whatever framework you used. That precisely means: an otherwise legal
> operation applied to a tree may kill it.

I am not a tree-specialist.

> It is so with all complex structures.
[snip integers]

A correct model would have the constraints in place to preserve the invariant of the structure while allowing all valid modifications. How to do that is out of my league.

I tried modeling the C3 MRO relationally but haven't found a solution (or the conviction that it can't be done) yet.

and (background)

It is a nice (and IMHO very useful) challenge. Any takers? Received on Fri Jun 23 2006 - 16:48:45 CEST

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