XML in a Nutshell, 3rd Edition

The include Element

The key component of XInclude is the include element. This must be in the http://www.w3.org/2001/XInclude namespace. The xi or xinclude prefixes are customary, although, as always, the prefix can change as long as the URI remains the same. This element has an href attribute that contains a URL pointing to the document to include. For example, this element includes the document found at the relative URL AlanTuring.xml:

<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" 
            href="AlanTuring.xml"/>

Of course, you can use absolute URLs as well:

<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" 
  href="http://cafeconleche.org/books/xian3/examples/12/AlanTuring.xml"
/>

Tip

Technically, the href attribute contains an IRI rather than a URI or URL. An IRI is like a URI except that it can contain non-ASCII characters such as é and . These characters are normally encoded in UTF-8, and then each byte of the UTF-8 sequence is percent escaped to convert the IRI to a URI before resolving it. If you’re working in English, and you’re not writing an XInclude processor, you can pretty much ignore this. All standard URLs are legal IRIs. If you are working with non-English, non-ASCII IRIs, this just means you can use them exactly as you’d expect without having to manually hex-encode the non-ASCII characters yourself.

Normally, the namespace declaration is placed on the root element of the including document, and not repeated on each individual xi:include element. Henceforth in ...