Late Night PC

The XPointer Scheme Registry didn't sound like that big a deal to me when I first saw this notice. But I needed something to read while watching my kid at skating (no wifi in the arena :( ). I didn't know what I was looking at when I started reading the XPointer Framework Recommendation since I had no context other than the announcement. By the time I was done, this is what I guessed. XPointer sounds like a replacement for the optional part after the '#' in a URL. That's a short explanation for casual observers like me. The long explanation is in the spec itself. XPointer Framework still allows a reference like http://www.example.com/report.html#part3, where 'part3' is the id of some anchor in the document. The section we're linking to in report.html is the part that looks something like <a id="part3">Part 3 </a>. That's the backward compatible part. XPointer Framework also describes how to handle DTD-defined id attibutes, so XHTML documents are covered as well. All the backward-compatible uses of the XPointer are covered as shorthand pointers, I believe. The fun begins with the new idea of allowing Scheme-Based Pointers, as described in section 3.3. The scheme based pointers allow an XML language to define their own meaning for the anchor part of a URL (or URI or IRI to be accurate). You just do the binding to the namespace at the start of the pointer with xmlns in a way that's analagous but syntactically different from the use of xmlns to include a namespace in an XML document. I'll come back to the binding bit in a minute, that's what the announcement I saw was actually about. Using a scheme-based pointer lets you do things that make sense in the context of the language you're using and put a reference to that thing in some other XML document. For example you can reference a WSDL interface or a specific view in an SVG document. Now about the namespace binding. The two examples that I gave (WSDL interfaces and SVG views) will get a "global" name in the XPointer Schemes Registry (they're being reviewed right now, at least). With a name in the registry, the namespace is bound without using xmlns, you'll just refer to svgView or wsdl.interface. Don't ask me why this excites me, it just does... One final thing to note. The XPointer Framework recommendation I'm talking about is separate from the XPointer recommendation itself. The whole thing is part of the XML Linking Working Group activity which finished up years ago. The only news here is the XPointer Scheme registry, which allows new XPointer schemes into this namespace.