How do I define HTML entity references inside a valid XML document?

If you can modify the the XML to include an inline DTD you can define the entities there:

<!DOCTYPE yourRootElement [
    <!ENTITY bull "&#8226;">
    ....
]>

I'm not cetain, but I think the XHTML DTD's should give you quite a few entities (253):

http://en.wikipedia.org/wiki/List_of_XML_and_HTML_character_entity_references#Entities_representing_special_characters_in_XHTML

Also in the w3 spec, there is a mention of additional DTD's for special characters etc. http://www.w3.org/TR/xhtml-modularization/dtd_module_defs.html#a_dtd_xhtml_character_entities

However I haven't been able to find an implementation example of the special character DTDs.

---

Edit by DevNull

Here is an extremely generic example implementation of one of the entity DTD modules. To implement, you only need to add a parameter entity pointing to the module.

<?xml version="1.0"?>
<!DOCTYPE test [
<!ELEMENT test (#PCDATA)>
<!ENTITY % xhtml-special SYSTEM "xhtml-special.ent">
%xhtml-special;
]>
<test>Here is a left double quote: &ldquo;</test>