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RE: datatyping is not needed

From: Jim Davis <jdavis@parc.xerox.com>
Date: Mon, 20 Jul 1998 19:52:30 PDT
Message-Id: <3.0.3.32.19980720195230.009a1310@mailback.parc.xerox.com>
To: www-webdav-dasl@w3.org
At 05:58 PM 7/20/98 PDT, Babich, Alan wrote:
>I presume that you mean to drop data type indications from the query schema 
>discovery, not just the query itself (select, where, and sortby). I presume
>that this also means you withdraw the offer of compromise that you and I 
>nearly reached on the QSD.

No, not yet anyway.  If it turns out that datatype is never used in
queries, then I would consider removing it from QSD.  On the other hand, I
think there's a valid argument that providing it in QSD is both very cheap
and provides some real (even if small) benefit to clients, so it might be
worth providing as a *hint*.  But we need to settle the query issue first,
since clearly if datatyping *is* ever allowed in a query, that strengthens
the argument for putting it into QSD considerably.  Even if datatype is not
allowed in the query, it might still go into QSD.  Indeed, I can see
incorporating even more metadata, along the lines of the
PropertyDescription object in DMA, or perhaps the Metadata Repository used
by the Stanford digital library protocol.  So please consider QSD an open
issue for now, but let's settle the issue of whether it belongs in queries.

The remainder of your email message lays out a major premise I would
paraphrase as "divergence from past accepted practise is dangerous".  The
minor premise I don't understand so clearly, it is something like "past
accepted practise is 'query conditions and order by on scalar values that
are of one of the 5 fundamental datatypes (integer, string, etc.)'".

Does this argue for datatyping in the QSD, or in the query? If the former,
I think you've stated the case for use in the QSD well already, so please
don't repeat it.  If the latter though, it needs more explanation.

Of course, all things being equal, trying anything new is risky.  But in
this case, we seem to not have the luxury of just repeating the old and
familiar.  If tried and true SQL (or Z39.50) were good enough, then DASL
could just be a Web encoding of one of those, and we'd be done.  Like it or
not, WebDAV has already made some design committments, e.g. that
resourcetype is an XML element not PCDATA.  We have to support those.  DASL
is, first and formost, a query for the model that WebDAV exposes, not for
RDBMS.  We can't assume the underlying store is tables.

My emails have shown why datatype is not needed in queries for "live" and
"famous dead" properties, and why it's harmful if adopted for the "obscure
dead", and why there is scarcely any problem by treating the dead as mere
strings.  If you - or anyone else - have counter arguments against any of
these, please state them.

best regards

Jim




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Received on Monday, 20 July 1998 23:04:53 GMT

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