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RE: [Alan Babich comments on] draft-reddy-dasl-protocol-00.txt

From: Jim Davis <jdavis@parc.xerox.com>
Date: Sat, 14 Mar 1998 18:54:58 PST
Message-Id: <3.0.3.32.19980314185458.007ed4f0@mailback.parc.xerox.com>
To: www-webdav-dasl@w3.org
At 06:18 PM 3/13/98 PST, Babich, Alan wrote:
>First, if I understand what you've done, you've chosen 
>prefix notation.

Glad you like it, but we don't deserve any credit for it, since it was
forced on us by our choice of XML.  If you're new to XML, some good
references are 
 http://www.sil.org/sgml/xml.html
 http://www.w3.org/TR/PR-xml
Also if you look at the current WedDAV spec it includes the full DTD for
WebDAV, so you can use the DTD instead of BNF it will help the discussion.

Next, you propose to introduce operators that are explicitly typed.  This
may be a good idea in the long run but I see two problems with the
particular approach you've suggested.

First, there's no mechanical way to tell what datatype each operator
accepts.  It's not okay for programs to guess by parsing the name, e.g.
inspecting  gt_integer and noticing the "integer" after the underscore.

Second, what would you do for operators that take operands of more than one
type, e.g. the (perhaps contrived) "length_lt" operator which take a string
and an integer and returns true if the string's length is less than that of
the integer.  (Of course in a real programming language one would write (lt
(length str) int) but we have only a query language here.)

The other syntactic simplifications you propose seem very sound to me.

I'd be grateful to have your comments on the proposal for query schema
definition.  We don't have access to the powerful self-description of DMA
in DAV, but I still hope to approach it when we can.

Best regards

Jim
Received on Saturday, 14 March 1998 21:55:34 GMT

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