<header> and <footer>
These two tags are straightforward. I'll wrap them around the contents of any custom HTML specified with the arg.hdr and arg.ftr DITA parameters.<article>
The HTML5 specification describes an article as being "a self-contained composition in a document, page, application, or site that is, in principle, independently distributable or reusable". That seems to closely match the DITA concept of a topic. So there are two possibilities:- Don't use <article> at all in the generated HTML5, except if topics are being chunked together in a single physical file.
- Start the body of each topic with <article>, for example:
<body> <article> ... <article> </body>
<section>
In HTML5, a section is used to logically subdivide a document or article:
This clearly corresponds to a DITA section, which "represents an organizational division in a topic".
<nav>
The HTML5 spec says that nav is "a section of a page that links to other pages or to parts within the page". The purpose of introducing such tags to HTML5 is to indicate to search engines that they don't need to index the content in them, so speeding up searches. Although it doesn't quite match because the links are not internal, I think this is a good match for the related links section of a DITA topic.<aside>
This new HTML element represents "a section of a page that consists of content that is tangentially related to the content around the aside element, and which could be considered separate from that content". It's plainly important that content in the aside is distinctly styled: for example, as a right-aligned sidebar in printed material, or as a floating box with a distinctive background color or border in a web page. So perhaps the best match in DITA terms is the abstract element.<hgroup>
This element is supposed to group consecutive headers together, for example:<hgroup>
<h1>Main Title</h1>
<h2>Secondary Title</h2>
</hgroup>
Stacked headings with no intervening text are considered bad practise in technical document, and DITA's DTDs reinforce that by not allowing them. The only time it could happen in DITA is when the titlealt element is used to provide an alternative header (for example, one that appears in search results or in a table of contents). But only one of the titles appears in the document at any one time. So I'm inclined not to use hgroup at all.
