This sets up the namespace for all the elements you used, which are of course all part of the RELAX NG syntax. datatypeLibrary lets the schema know where to pull data types (covered in the “Data types” section later) from, when you type elements and attributes.

You can use the value-of construct to obtain the value of an element, and provide the element name to match through the select attribute. In the example, the character data within the title element is extracted and used as the title of the page, and a link is constructed using the link element as the target. On the other hand, when you want to cause the templates associated with an element’s children to be applied, use apply-templates. Be sure to do this, or nested elements can be ignored! You can specify the elements to apply templates to using the select attribute; by specifying a value of * to that attribute, all templates left will be applied to all nested elements.

You can’t have one without the other; at least, not without introducing tremendous room for error. An instance document without a schema must be interpreted by the recipient; and do you really want him deciding what your elements and attributes meant? ” That’s a good goal, but practically impossible. As a programmer, I often think my code is well documented and easily understood; but I’m assuming a certain level of expertise, and a certain approach to coding. Change just a few bits here and there, and someone else might reasonably interpret my “well-documented” code (or XML) completely differently than I might.

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