[RFC2518 Issue] PROPFIND 'allprop' usage from Lisa Dusseault on 2000-11-10 (w3c-dist-auth@w3.org from October to December 2000) (original) (raw)

Past discussions have shown that servers frequently have trouble implementing PROPFIND 'allprop'. Jim asked me to summarize the past discussion & list the open issues so that we can get this fixed, if it can be fixed, in revisions to 2518.

There are already cases where not all properties will be returned: RFC2518: "In the case of allprop and propname, if a principal does not have the right to know whether a particular property exists then the property should be silently excluded from the response."

John Stracke's proposal for reducing/specifying the scope of 'allprop', and discussion of the motivation:

It has been a point of discussion for Advanced Collections:

http://lists.w3.org/Archives/Public/w3c-dist-auth/1999JanMar/0008.html "Clients need to know whether the property is computed on the fly before requesting it. There is no way to find out. The impact of computing on the fly is especially significant when a client requests allprop. There may be other properties that are computed on the fly as well. DAV:getetag is computed, and some versioning history properties may also be computed."

Also in Versioning:

http://lists.w3.org/Archives/Public/w3c-dist-auth/1999JanMar/0075.html "There has also been a massive growth in the number of available DAV properties. PROPFIND allprop operations may lead to very large responses even with Depth: 1, which would slow down performance for users due to network speeds. It might be worthwhile to add this facet to the open issue ALLPROP_AND_COMPUTED."

Also in ACLs, Babich argues that clients who request 'allprop' don't really want to see the ACL property, thus they ought to specifically ask for it.

http://lists.w3.org/Archives/Public/w3c-dist-auth/1998JulSep/0101.html

Several server implementors have voiced the opinion that 'allprop' should be "put out of its misery" (GMC) or at least weakened. Often this is because of standard or custom properties that must be calculated by the server (e.g. 'lockdiscovery'), and the calculation can become extraordinarily expensive with an 'allprop' of depth: infinity.

The only server-side argument for keeping 'allprop' is that server-to-server COPY requires it; but if anybody has implemented this yet and can't use 'propname' instead, please speak up.

Summary: There thus seems to be a consensus among server implementors and those designing new features for DAV. What's missing in order to resolve this issue for fixing RFC2518 is input from clients.

Is anybody aware of clients that rely on particular properties being returned in 'allprop'? If the properties relied upon include any more than the set DAV:{creationdate, displayname, getcontentlanguage, getcontentlength, getcontenttype, getetag, getlastmodified} (the properties required for DAV level 1 support) I would be very surprised. Thus, servers may be able to restrict the required property set to this set.
Is anybody aware of clients that rely on 'allprop', rather than 'propname', for property discovery? This would be a more serious issue if major client implementations actually rely on doing property discovery using 'allprop', and attempt this against various implementations of WebDAV servers.

These seem to be our options for modifying RFC2518 (remember, it has to be a simple mod):

deprecate 'allprop' and tell clients not to use it, but to use 'propname' instead
define 'allprop' to be the set of properties required for DAV level 1 support (although servers could freely return more properties if desired)
explicitly allow servers to return an error code (507?) for properties that were too expensive to calculate for a 'allprop' request, but still allowing the client to do property discovery through 'allprop'

Please voice your preferences among these options, objections, or other ideas.

thanks, Lisa Xythos

Received on Friday, 10 November 2000 13:38:27 UTC