XML in a Nutshell, 3rd Edition

Including Text Files

By default, the XInclude processor assumes the document pointed to by an href attribute is a well-formed XML document. This document is parsed, and the content of the included document replaces the xi:include element in the including document. However, it is also nice to be able to include unparsed text when assembling a larger document. For instance, the program and XML examples in this book could be included directly from their source form. If you add a parse attribute to an xi:include element with the value text, then the document will be loaded as plain text and not parsed. For example, this element includes Example 12-1 as plain text, without parsing it:

<xi:include 
  href="http://cafeconleche.org/books/xian3/examples/12/12-1.xml"
  parse="text"
/>

When parse="text“, it is no longer necessary for the referenced document to be well-formed. Indeed, it need not be an XML document at all. It can be C source code, an email message, a classic HTML document, or almost anything else. The only restriction is that the included document must not contain any completely illegal characters, such as an ASCII NUL, or an unmatched half of a surrogate pair.

XInclude processors make use of any protocol metadata such as HTTP headers to determine the encoding of a referenced document so they can transcode it into Unicode before including it. If external metadata is not available, but the MIME media type is text/xml, application/xml, or some type that ends in +xml, then the processor ...