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2/17/2002 1:34:28 AM, "Gary Stephenson" <garys@ihug.com.au> wrote:
>
>How "truthful" is the analogy of considering the entire world of
>URI-addressable HTTP resources as one gigantic database, the HTTP protocol
>itself as the DBMS, and URIs as the key-values. Is the analogy close enough
>to warrant further scrutiny of the best practices in the DBMS world? Does
>the success of CGI systems indicate, at least in part, the usefulness of the
>analogy?
Hmmmm ... it's certainly not a *relational* DBMS, maybe a giant CODASYL-like
DBMS ... but I've been wondering about Date's vehement objection to
"pointers" in the context of XML too. I think he's probably onto something,
and having some way of "JOIN-ing" web resources based on value comparisons
rather than chasing pointers will probably add a lot of value ... someday.
BTW, could you elaborate on "the success of CGI systems" ... not sure
how that relates.
>
>I also suspect that a fuller understanding than my own of exactly why Date
>is so adamantly against ObjectIDs (aka references/pointers) appearing as
>part of the logical data model would provide useful insights on some of the
>issues surrounding URIs vs URLs/URNs, entities vs. resources, and the
>further development of REST-ful best practices.
Thanks for jumping in! This is a very interesting thought, IMHO. A few
random comments ...
- Date is rather adamant that the computer/database industry has limited
itself by hacking on a failed database model (hierarchical/network) and
grafting on faddish OO notions rather than fully implementing and
appreciating the relational model. The obvious rejoinder is that
the industry builds on what actually works in practice, and the market
weeds out those who can't make their ideas generate actual economic
value for their customers. I sometimes wonder if Date's
canonical rant isn't analogous to someone channeling Turing and saying
that we should all stick to the conceptual model of an infinite tape
that reads and writes marks and moves forward or backward .... since
that is elegant, provably correct and universal.
- I'm not sure what the practical limit on the number of tables that
current RDBMs can JOIN across, but it is quite a few orders of magnitude
less than the number of "resources" on the internet. The Web,
hack though it may be, actually WORKS!
- Could a DBMS the size of the Web apply Date's principles and/or
DBMS best practice without solving the "type" problem? A pointer
doesn't care what it points to, but a JOIN implies some congruence
of the values being joined ... not to mention the foreign/primary
key constraints, right?
- I do think that the "use RDBMS theory and best practice" could indeed
apply to metadata management more than current practice indicates.
I can't sit through an RDF presentation without thinking very similar
thoughts to those that Gary Stephenson posted ..."Hmmm, this sounds
a lot like the stuff that Date rails against ... mightn't these folks
learn a lot from studying the relational model and improving on its
limitations rather than inventing network databases over again?"
The best "here's why not" answer I've gotten to this (I remember it
was from Michael Kay) is that RDF itself is normalizeable into relational
form but SQL can't practically handle the recursive queries it would
take to answer any interesting questions about the knowledge the
RDF represents. Date, not surprisingly, implies that this is
a limitation of SQL, not the relational model, and that the way
forward lies in actually implementing a relational database as
Codd defined it.
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