I saw something the other day that I was both intrigued and bothered by in equal measure. 'Mozilla and the Khronos Group Announce Initiative to Bring Accelerated 3D to the Web'.
Mozilla will work with the Khronos Group to extend the exploration process of what an initial take of 3D on the Web should look like to a wider audience.
Despite the years spent developing client-side code, I'm an unashamed fan of the XML stack and because of it, the declarative web too. Many people have put a considerable amount of effort into making content mark-up both rich in semantics, just look at DocBook and XHTML 2, and extensible through the adoption of XML Namespaces and open Schemas. User input and client-side logic is well served by XForms and presentation extends these formats on many levels via CSS. Other modes of delivery, like print, are catered for by XSL-FO. Richer and more interactive experiences can be delivered either in-line or out-of-line using SVG and SMIL. Where fully supported, many of these formats can be freely inter-woven because of, rather than in spite of, XML Namespaces.
Content can be aggregated with XInclude, stored and syndicated with Atom and validated either by grammar using XML Schema or via rules with Schematron. All the afore mentioned XML languages can themselves be created and transformed using XSLT, which being XML itself can also create and transform itself, and all of this built upon a common foundation of XML, XPath and the URI.
Where people interact with content there is a responsibility to provide access to as wide an audience as possible; ARIA Roles and Status help convey, via the user-agent, the nature and state of the content being experienced at that time. Bring into the mix, annotations via RDFa that add to the semantics, richness and machine-readability of the data that lies both within the content and beyond in linked data/content and you'll start to see that the vision of a web of content and data is being realised all around us.