Quote:
Originally Posted by Nate the great
Epub isn't XML; it has XML as one of its parts. But it also has HTML tags. A strict XML file shouldn't have anything other than XML tags (I think)*.
* Could someone correct me if I'm wrong?
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You are somewhat wrong. EPUB has XHTML tags (and syntax), not HTML ones. And XHTML is XML (unlike HTML which is SGML).
XHTML attempts to be a semantic language. XHTML has well-defined DTD and can be validated. Most HTML presentational attributes and tags are either outlawed (e.g. FONT) or deprecated (ALIGN). Instead, CSS stylesheets do the job. In addition, classes can be assigned to add your own semantic structure on top of what XHTML provides.
In reality, a lot of XHTML content is just somewhat tidied-up presentational HTML - and that looks really ugly on the source level. It is still XML, but there is not much sematics in it, it is just styled to look right. I consider this to be bad authoring practice, but that's somewhat a question of opinion.
There is no such thing as "XML tags". Better to say, there are no tags defined by XML specification itself. XML defines how to build various XML dialects - and XML dialect is where tags are defined. XHTML is merely one of such dialects that tries to make transition from HTML simple. (SVG and DTBook, also mandated by EPUB spec, are also XML dialects).