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RE: ANY in the DASL spec

From: Saveen Reddy (Exchange) <saveenr@Exchange.Microsoft.com>
Date: Tue, 21 Apr 1998 11:29:34 -0700
Message-ID: <2FBF98FC7852CF11912A00000000000107E78582@DINO>
To: "'Judith Slein'" <slein@wrc.xerox.com>
Cc: www-webdav-dasl@w3.org

I claim the the reasons you say ANY is worse actually cause it to be better
...

If only Prop is allowed then a > operation could only look like this
(ignoring literals for the moment)

	propname1 > propname2

But never
	
	propname1 > ( propname2 * 10 )

And similarly, extension for other kinds of server-specific functions is not
allowed ...

	propname1 > foo:baroperator ( propname2 , 10 )

Whenever ANY appears (as it does for DAV:prop) we are going to have to
supplement the DTD with sections in the draft that elaborate on the
restrictions and interpretations -- this is true for both ANY and DAV:prop.
Because they both equal ANY then I claim there's no point adding an extra
DAV:prop layer to contain the property name.

-Saveen

-----Original Message-----
From: Judith Slein [mailto:slein@wrc.xerox.com]
Sent: Tuesday, April 21, 1998 7:32 AM
To: Saveen Reddy (Exchange)
Cc: www-webdav-dasl@w3.org
Subject: RE: ANY in the DASL spec


I think the grammar has to be as specific as possible.  Whenever we say
ANY, an implementer really can put any construction of defined elements
there, and it will be valid.  We should not say this is valid unless we
really mean it.  I think readability is not a criterion for a good grammar
definition (unless we are deciding between two logically equivalent
expressions, one of which is more readable than the other).

You are right about the where element definition -- since extensibility is
desired, there is probably nothing for it but to define where to be ANY,
and explain in the text what sort of elements are really acceptable.  You
have done a nice job of this.

It's true that in the operator definitions, prop would not be ideal because
we still have to explain in text that only single-valued instances of prop
are allowed, but ANY is even worse, since it allows multi-valued prop
elements and all sorts of other stuff like from elements, sortby elements,
etc.

--Judy

At 02:24 PM 4/20/98 PDT, Saveen Reddy (Exchange) wrote:
>Going to DAV:operator instead of any I think induces two problems:
>
>1 - makes the grammar more unreadable. I know this is in some ways not a
big
>deal -- no user will see these queries, but having a lot of XML:elements
>makes it confusing. People, by far, wanted the "low-fat" grammar in "01"
>than the original "00" grammar.
>
>2 - And this is the more serious concern ... I think this limits the
>extensibility. The point of saying ANY in this case was to allow search
>arbiters to easily extend the search grammar. If they needed to have a new
>operator they can implement one and expose it as a namespaced XML element
>without fear of interfering with other operators. 
>
>As for moving DAV:prop and DAV:literal for all the search operators I think
>this doesn't add any new capability -- if the element isn't DAV:literal
then
>there is nothing else it can identify except a property. Adding a prop
>element in this case is also perhaps harmful ... DAV:prop is defined to
>potentially contain multiple properties, not a single property.
>
>-Saveen
>

Name:			Judith A. Slein
E-Mail:		slein@wrc.xerox.com
Internal Phone:  	8*222-5169
Fax:			(716) 422-2938
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Web Site:    http://www.nde.wrc.xerox.com/users/Slein/slein.htm
Received on Tuesday, 21 April 1998 14:29:35 GMT

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