XML in a Nutshell, 3rd Edition

XPointers on URLs

A URL that identifies a document looks something like http://java.sun.com:80/products/jndi/index.html. In this example, the scheme http tells you what protocol the application should use to retrieve the document. The authority, java.sun.com:80 in this example, tells you from which host the application should retrieve the document. The authority may also contain the port to connect to that host and the username and password to use. The path, /products/jndi/index.html in this example, tells you which file in which directory to ask the server for. This may not always be a real file in a real filesystem, but it should be a complete document that the server knows how to generate and return. You’re already familiar with all of this, and XPointer doesn’t change any of it.

You probably also know that some URLs contain fragment identifiers that point to a particular named anchor inside the document the URL locates. This is separated from the path by the octothorpe, #. For example, if we added the fragment download to the previous URL, it would become http://java.sun.com:80/products/jndi/index.html#download. When a web browser follows a link to this URL, it looks for a named anchor in the document at http://java.sun.com:80/products/jndi/index.html with the name download, such as this one:

<a name="download"></a>

It would then scroll the browser window to the position in the document where the anchor with that name is found. This is a simple and straightforward system, and ...