A lightning talk at the tech plenary is about 3 minutes long and introduces something very specific to the W3C.
I gave a lightning talk on the effecs of adding or changing the stuff in a namespace. You can see the diagram and notes here: http://www.w3.org/2006/03/01-Boyer-Lightning/SignaturesAndNamespaces_Boyer.html
Basically, got a lot of nods all the way up to TimBL himself when I said you either have to use a new namespace, or you have to internally version the language so that old processors for a vocabulary don't try to render new documents with graceful degradation of unrecognized content when the documents have been signed.
Too bad this is exactly what happened with xml:id. It got added to the XML namespace rather than some other namespace, and the version of XML didn't change. Lo' and behold, it broke something. When doing a C14N of a document subset containing orphaned nodes, C14N copies XML namespaced attributes into orphaned nodes when they don't contain their own settings for the nodes.
This is good for xml:space, xml:lang and xml:base, but it isn't good for xml:id.
Truth be told, it's kind of an edge case. In XFDL, we don't even allow you to orphan nodes when signature filtering because the structure of the language is such that an orphaned node is useless without its ancestral chain.
Still, while the problem doesn't affect Workplace Forms, we (in W3C capacity) will still endeavor to fix the problem.
Since the ship has already saled on what namespace xml:id lives in, we're going to be doing a new C14N algorithm that doesn't do the inheritance behavior on xml:id OR one that doesn't do the inheritance behavior except for lang, space and base.
Actually, it's a little more complicated than that, since either of the above choices means that C14N will again be broken in the future when either a non-heritable or a heritable attribute, respectively, is added to the XML namespace.
I think we may have to add a parameterization to the new C14N that allows the author to specify the heritable attributes. This will allow document authors to keep up with adjustments to the XML namespace.
The core WG feels that further additions to the XML namespace are highly unlikely, but I'm not convinced. Just at this tech plenary alone, I heard calls for xml:role (like HTML's role) and xml:profile (like DOM's hasFeature, it would declare that a document has a feature so the processor needs to have the feature or the document won't work). In the past, I've heard a need for xml:src (like HTML src, except HTML's default is wrong-- content should override the attribute rather than the reverse). And my personal fave would be xml:compute to express that the content of an element is computationally derived from other content. The list really does go on once you start to think about XML as an intelligent object...
Signatures and Namespaces
John M. Boyer 060000VMNY 831 Views