Re: [Simple] XCAP and its problem with Namespaces caused by using only the XML fragment body.

On Tue, 2005-08-16 at 20:57 -0400, ext Jonathan Rosenberg wrote:
> inline.
> 
> Hyttfors, Per wrote:
> 
> > Hello,
> >  
> > As I see it there is a major problem with retrieving elements in an XML 
> > document using XCAP. The problem has to do with that the XDM clients has 
> > to know all the namespace prefix bindings in the server document prio 
> > the fetch of an element.
> >  
> > The problem is that the current XCAP specification only mandates that a 
> > XCAP fragment body is sent between server and client when performing 
> > XCAP operations. Not being an fcs document with the fragment context 
> > specification leads to problems now when the XCAP URL has been made 
> > independent of the namespaces prefixes used in the document on the server.
> >  
> > The XML data returned in the 200 OK answer on a fetch of an element will 
> > contain the exact content of that element in the XML document on the 
> > server. If this element or any child elements use namespace prefixes 
> > declared earlier in the document they will not be included in the 
> > response to the client. Hence the only way to know all the prefixes is 
> > to have done a fetch of the whole document.
> 
> The client doesn't need the whole document; it just needs the portion of 
> the document above the element that has been fetched, in order to know 
> the namespace bindings that are in scope for the element that is being 
> fetched.
> 
> I'm assuming that you have in mind an application where the client 
> doesn't normally store the whole document, for example a cell phone 
> where I want to retrieve portions of my buddy list one buddy at a time.
> 
> As such, one solution is to fetch the whole document at startup, get the 
> namespace bindings and etag, and dump the document. Then, subsequent 
> GETs are conditional against the etag, and so the client can get the 
> information it needs and use the cached namespace bindings.
> 
> This is clearly not optimal since it requires a full document get just 
> to obtain the namespace bindings. However, it works with the current spec.
> 
> Some other thoughts are:
> 
> 1. an xcap extension that allowed to specifically query for the 
> namespace bindings in scope for a particular element
> 
> 2. change xcap so that what is returned is an xml fragment that includes 
> additional information on the namespace bindings in scope
> 
> 3. have the xcap server return xml data using the namespace bindings in 
> scope for the request URI. This requires the server to modify the xml 
> data before sending it to the client
> 
I suppose this question has come from OMA people. An XPath way of doing
this could be GET ....~~/root/namespace::*, i.e. namespace axis could be
used to request all the in-scope namespaces of some element. An XCAP
extension should then describe this BNF extension as well as the payload
format.

br,
Jari


_______________________________________________
Simple mailing list
Simple@ietf.org
https://www1.ietf.org/mailman/listinfo/simple