[whatwg] Entity definitions in XHTML

[David Carlisle]

This is a further attempt to resolve the bug report (currently with
status  wontfix) regarding XHTML entity definitions.

(whatwg)
https://www.w3.org/Bugs/Public/show_bug.cgi?id=17798

(w3c)
https://www.w3.org/Bugs/Public/show_bug.cgi?id=13409

By adding

"-//W3C//ENTITIES HTML MathML Set//EN//XML"

To the list in

13.2 Parsing XHTML documents

Of Identifiers that are recognised when parsing XHTML syntax documents.

The current list gives no way to specify the identifier of a
compatible set of entity definitions so makes it highly likely that
documents will be interpreted differently by an XHTML user agent and a
standard XML toolchain. This is bad considering that being able to use
xml tools on the document is about the only reason for wanting to
serve the document as xhtml rather than text/html.

Further rationale is given in a message on the w3c list here:

http://lists.w3.org/Archives/Public/public-html-admin/2013Jan/0021.html

But I wanted to flag it here as well as this list presumably reaches a
different audience.

In particular a question for implementers, would adding

"-//W3C//ENTITIES HTML MathML Set//EN//XML"

to the list of recognised doctype PUBLIC identifiers be
impossibly hard, trivially easy, or inconvenient but you'd do it if
the spec changed?



Ian said in the original bug (comment 11)

 > I'm happy to add new DTDs to the list; all you have to do is show that
 > the URL you want to add already works in the majority of deployed
 > browsers. To do that, please simply provide trivial test cases that
 > use the DTD you want to have supported. It's not clear to me from this
 > bug so far what exactly it is you want changed in the spec.

However "already works" is a rather impossible criterion for fixing
this problem. There were previously doctype declarations that worked
(as witnessed by the XHTML version of the MathML2 spec) but current
browsers have converged on the list as specified in HTML so
implementations have followed the spec which means it is now not
possible to use entities in XHTML if you specify a DTD that defines
them, but is if you specify a DTD that does not.  Adding one extra
recognised PUBLIC identifier gives a way that documents may be
produced that work on pre-html5 browsers and browsers updated to
recognise the additional string and also work with standard xml tools.


http://www.whatwg.org/specs/web-apps/current-work/multipage/the-xhtml-syntax.html#parsing-xhtml-documents



David

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