Why isn’t XInclude supported by any browser?

I’m wondering why no web browser supports the XInclude standard for XHTML.

This standard exists for almost five years, and I think it would be very useful for the web. For example, you could XInclude the static parts of your web site, such that the browser will only need to download the part which have changed when the user is browsing the site. Moreover (but I may be wrong) this does not seem to be very difficult to support, in comparison to standards like SVG or MathML.

(sorry for this questio开发者_StackOverflow社区n without real answer, I will not mind if it is closed)

There is an old open bug on the Mozilla bug tracker asking for XInclude support with a patch in which some problems are discussed:

• a satisfactory XInclude implementation requires XPath, XPointer, xml:id and other specs to be implemented first,
• most of the time XInclude can be simulated by the document() XSLT function,
• loops must be detected and this is hard to do,
• it is not well understood how the DOM changes made by XInclude's documents should be encapsulated into events and propagated.