Authoring help
This section is a brief guide to the main elements used in this Saxon documentation which
            conforms to the HTML-5 article element.
The article element is the top-level element in the XML document. It must
            have an id attribute that corresponds to a ref attribute value
            found in the catalog.xml file. The title attribute is what
            will be shown in the table of contents and other links.
Introductory text goes inside the top-level article element - normally, this will be
            headed by an h1 element as the heading for the article (which may be the
            same as the title attribute of article). Navigation links can
            also be added for all child topics in the article using
                <nav><ul/></nav>.