[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] RE: XLink embedding (was Re: W3C XML Schema best practice : inclusions)
Hello Uche Uche said: Eh what? I don't think it's a good idea to override the server's specified TTL. If the provider doesn't know how to use HTTP, it's a problem you should take up with them. Any service provider that set their TTL to 0 in a misguided attemp to improve hit count, or any other such trickery would probably eventually get yelled at by users. Even if this is something you _absolutely_ have to have this override in the consumer, I think that is a highly application-specific matter that should not be addressed by the XInclude or XLink. Didier replies: Why is this a wrong idea? practically speaking a lot of content's TTL is not well set. If, for instance, you need to aggregate contents to create a portal, then you'll probably will have to set the TTL yourself otherwise, the time required to get the content is too long. But you are right, the publishers are supposed to do their job right and to define caching mechanism in recommendations is not necessarily a good idea (like saying to somebody that he's not doing his job well :-) However, practically speaking it is needed for some kind of application needing to aggregate contents. Anyway, a particular app may inherit the xinclude behavior and add the caching override. Good point Uche. Uche said: Is this realistic to expect? It's certainly hard to imagine this scenario with XSLT stylesheets, since XSLT processing tends to be highy non-linear. It's certainly possible with CSS, but are the saving worth the processing complexity in the user agent? Didier replies: Wrong, it is possible with XSLT - I did it in my labs, and it is working very well. The only problem today is that the transformation scope is for the entire document. To limit the scope to a fragment may help to have the inclusion/transformation to occur in parallel. Off course this applies only the xinclude construct, not to the xlink construct since the inclusion (show="embed") occurs only when the user clicks on the link. Off course, a lot of actual XML processing will have some problems with parallel processing, but this is an implementation issue not an XSLT language issue. Inclusions/transformation may be performed in parallel. By the way, to limit the scope of transformation to a document fragment brings the notion of document component. For instance, I can request a web service for a calendar to be embedded in my XHTML document. If we limit the transformation to this inclusion, we embed a component. For instance, the calendar data may be displayed as a table (month view), as a list (day view). Also, when we think inclusion/transformation, we also have to think about partitioning, can we partition the processes on the requester or on the provider? Transformation may be partitioned on the basis of different parameters like the business model, processing capabilities, etc.. in conclusion, yes it make sense - in the case of inclusion - to perform a transformation at a document fragment level and this can occur in parallel (only if the transformation scope is at the document fragment level and limited to the included content, not including the host document) Uche said: Sounds as if this could be at least partly handled by content-negotiation at the transport layer. maybe it would be nice to have an extension mechanism for transport-level parameters in inclusions and linking. Then my implementation could extend the spec to support a set of http-header attributes in the origin element that are tacked on the the HTTP request headers. Didier said: We have CC/PP as a work in progress (http://www.w3.org/Mobile/CCPP/) but no ways to use that in the context of inclusions. The inclusion may be based on the device capabilities. The data included may not be pertinent on certain devices. The problem though is to state that this inclusion is to occur only for certain devices. This is obviously more for xinclude than it is for xlink. Cheers Didier PH Martin ---------------------------------------------- Email: martind@n... Conferences: xml devcon 2000 (http://www.xmldevcon2000.com) Wireless Summit NY (http:www.pulver.com) xml devcon 2001 London (http://www.xmldevcon2000.com) Book: XML Professional (http://www.wrox.com) column: Style Matters (http://www.xml.com)
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