Alaric B Snell <> proposes:
<snip/>
> Clearly, this process can be generalised with an extensible lookup
> table to allow one to ship a module for web browsers that
> allows them to
> display, say, directly embedded SVG or RDF (as a graph of clickable
> links for nodes and arrows between them or something).
>
> XHTML itself would be just such a module; so some other
> renderer could
> find bits of XHTML embedded in it's input document as labels or
> something and pass control (via the lookup table) to the
> XHTML renderer
> for those.
>
> Thus, the web browser's rendering engine would boil down to
> invoking
> the correct module for the namespace of the root element and letting
> that module handle dispatch to other modules where appropriate.
A small nit: you'd want each module handing dispatch handling back to
the main "browser rendering engine" when it hit a namespace other than
it's own. That way the handling of module lookup would be done in only
one place instead of each module...
> The hard part for being able to define an extension architecture for
> every XML application domain (rendering, searching, etc) is
> choosing a
> generic API and a general meaning of 'embedding' for that application
> domain. Can this in general be done? I'd say "probably".
Watching the developments in Aspect Oriented Programming (AOP) go by I'd
say the likely hood is more than "probably": eg. the JBoss
implementation (and likely others?) allows XML definitions of method
overrides that allow you to change the parameter structure of a method
and give you (among other things) the equivalent of multiple inheritance
if you need it.
> However, expect
> problems where people overspecify stuff and accidentally produce
> non-extensible module APIs (perhaps something more general
> than the CSS
> box model is required to base rendering upon. Perhaps XSL-FO would be
> better).
The rendering issue is separate from the API extension issue, and
perhaps harder: I'd guess that you want something more generic such as a
than simple boxes, Bezier curves in addition to lines at least?
