Listing valid children/parents of HTML elements

HTML lists elements and classes of elements that are allowed to be children
of each element, and attributes. Wouldn't it be useful if this was shown
somewhere?

E.g. http://www.w3.org/TR/html5/semantics.html#the-html-element defines the
that the root 'html' tag contains a head tag, followed by a body tag.

Listing the relevant aria-* properties would also be nice.

Should I add fields for this to <
https://docs.webplatform.org/wiki/Form:Markup_Element>? And then make it a
Semantic Mediawiki statement so we can query e.g. "which elements is this
element found in."

Austin Wright.