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Null values

From: Jim Davis <jdavis@parc.xerox.com>
Date: Mon, 14 Sep 1998 09:50:07 PDT
Message-Id: <>
To: www-webdav-dasl@w3.org
DASL draft has two difference definitions of NULL, in 5.5.3 and in 5.11

5.5.3 says

A NULL value for a property identifies the following conditions:
- The property is not defined on a resource.
- The property is not set on a resource.
- The value of the property is UNKNOWN.
- Security policies prevent the retrieval of the property's value.

5.11 says

 The DAV:isnull operator is TRUE if and only if a PROPFIND response for the
property on that resource would return the 403 (Forbidden) or 404 (Not
Found) status code.

I think we should have exactly one definition of what it is to be null, and
I like the second definition better because it's based on observable
behavior of a lower level of the protocol.  Also the definition in 5.5.3 is
not very "DAV" like, in that in DAV there is no concept of a "schema" that
would say whether a property is "defined on" a resource, and there is no
way to set a value of a property to "UNKNOWN".  These are concepts that
appear in DASL because we know that some DASL servers will use SQL for
implementation, but DASL should use only the language of DAV.

Received on Monday, 14 September 1998 12:50:28 UTC

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