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From: "Dare Obasanjo" <kpako@y...> > I believe the thrust of Nicolas' question is where to find the RDDL document > for an XML file that utilizes names from multiple namespaces. No one has > proposed a *concrete* answer to that question yet although the designers of > RDDL may consider this to be beyond the design goals of RDDL which is > reasonable. RDDL answers "what is at the end of the namespace URI?" The resource at the end of the namespace URI for a RDDL document is an XHTML document. So the RDDL docuemnt that the XHTML namespace URL locates will not help us with RDDL. Instead, it gives us the typical or general documentation. And the schemas that may be located through a RDDL directory may also be the most general, or most typical, ones for a namespace rather than the particular ones we are interested in. I don't see it a fault of RDDL in this. It has been pretty well accepted since the big discussions of HTML's 3 DTDs that a namespace does not mean a schema. This has two connotations: first that the URL is too valuable to tie it to a single terminating type of resource only (e.g. the schema); but second that there can be multiple schemas possible (even in the same schema language) for the same resource--a namespace is not a language but a language family. Since a namespace is not a particular schema in a particular schema language we need to both try to support as much plurality as we can. So RDDL provides links so we can locate different language versions of a schema which (in some sense) is regarded as typical or canonical, while well-designed schema languages (such as W3C XML Schemas and ISO DTDs) support mechanisms for associating variant and particular schemas to a namespace (e.g. schemaLocation in XML Schemas). Each covers one aspect. So there is no mechanism for finding RDDL variants from a namespace URI yet. But that is not a problem with RDDL, it is just something extra that is needed. In DZIP[1] aka XAR, I am trying to resolve a very similar problem. How to bundle and transmit the particular application resources for a document type (which could have a characteristic namespace). There is as yet no method of tieing the XAR to a URL. Instead we just have a simple PI in the document <?XAR docbook?> which says to an application "use the application with the nickname docbook, as resolved by the application itself from whatever repositories or built-ins". I.e. track down a docbook XAR (perhaps from your system integrator), then load it. Incedentally, it is only by having some mechanism like this, I believe, that we can move beyond a passive acceptance of Microsoft's Derek Denny-Brown comment on this list that "Lock-in is inevitable, no matter what you do. " ... "The key to XML is not it's ability to avoid lock-in. It is it's ability to facilitate interop, and loosely coupled systems. " Why should we just lie back and enjoy it? With XML, if we reduce ourselves to just using the namespace URI directly for tracking down resources, we can only really get fairly vanilla and generic resources. Generic resources from namespace URIs are no threat to the kind of lock-in that Denny-Brown espouses. So I think Paul T and Nicholas are actually asking some good questions, even though they may be too ferocious that apples are not oranges. A namespace is not a document type, and we need better support of document types in order to build shrink-wrapped XML desktop applications. This is exactly where XAR can help. Integrators can bundle all the RDDL resources for a particular document type/namespace, and as well a system integrator can distribute appropriate application configuration files and binaries with it. We are prototyping this at the moment in our Markup Editor at Topologi: one can browse servers for various applications, download them, and they load the correct DTDs, schemas, RDDL documentation, and everything else. I hope other vendors will support XAR too. Cheers Rick Jelliffe Topologi, Pty. Ltd. [1] http://www.topologi.com/public/dzip.html
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