Add DTD/external entity support to Firefox

The need

Although Firefox was a pioneer in offering XML within browsers, the very basic facility of DTDs, used by many XML files for storing entities, has now become a 10-year old bug!

Such files are often used by those preparing TEI or Docbook documents and where certain symbols like copyright or accented characters are repeatedly used but for the sake of convenience, safety of character set transmission, or readability are not typed in directly each time. While Firefox does support internally-declared entities, it is quite cumbersome and difficult to maintain if one must paste in these entities for each file that uses them.

If you want to directly view in Firefox an XML document which references an external entity file, you are completely out of luck. Even Firefox’s own extension framework makes uses of the convenience of entity files, but entity resolution unfortunately does not occur for files on the web.

Specific bugs needing fixing

The most fundamental bug is that a missing entity will cause the whole file to fail, though this is against the XML specification:
https://bugzilla.mozilla.org/show_bug.cgi?id=204102

So, not only is Firefox unable to load the entities, but it won’t even show you the rest of your non-entity file content. XML does not allow this behavior, so this is a bug which should definitely be fixed.

Moreover, for those of us who do want the entity content to also be loaded, at the very least by option or user prompting (and taking into account security issues, perhaps even limiting it to loading from the same domain, though this is less than ideal and scripts are not similarly restricted), the following bug (which is admittedly really a feature request since XML doesn’t require loading of external entities) should also be addressed, as it is necessary for entities to be viewed.

For those concerned with entity loading slowing down the browser, this can be mitigated by either being performed only at user option (less than ideal) and/or by caching external files as is done with scripts and stylesheets (and works just fine for them).

While DTD Validation is less important (and should indeed not be turned on by default), it would still be nice to have as a feature since
1) No other validation is built-in to Firefox
2) Some older XML standards are still only expressed in DTDs
3) DTD validation is relatively easy (as well as standard) compared to certain validation languages, even if it is less expressive.

Finally, there is one other basic bug of which I’m aware which can cause problems for XML documents, in that even internal entity declarations will be ignored (and cause a single point of failure) if they are placed after an external parameter entity:
https://bugzilla.mozilla.org/show_bug.cgi?id=267350

Additional benefits

Such a universal standard as XML should not suffer from being able to be viewed and distributed on the web, whether it is use for specialized documents or data. External entities were envisioned as part of the XML standard, and at the very least, their usage should not cause a single point of failure (causing the whole document to be unviewable).

Another potential benefit of supporting the direct viewing of XML files is that specialized Firefox extensions can be made to search or browse full XML files in a variety of ways.

While Firefox understandably concentrates on the flashier features demanded by the masses such as video, faster web page rendering, etc., those of us working with rich semantic documents (often prepared with entity files) would very much like to see DTD facilities (particularly for entities) available to XML documents. As Firefox supports other XML standards, whether XHTML5, SVG, MathML, etc., these too could benefit from allowing custom entities.

Call to action

I don’t know how much the developers may require, but I intend to find the lowest bidder who can do the job well.