Good, and looking again at it I think the "language" business is
clear:
None of my OpenSearch descriptions support to restrict the language of
search results, therefore the default "*" is good enough.
I enforce "hl=en" in one case, and my descriptions generally use en-GB
(or similar) for keywords etc., but that does not affect the search
results.
You could still mention xml:lang somewhere as optional attribute for
all elements where this makes sense, notably the root element of any
OpenSearch description:
A given description normally has only one xml:lang, and that might be
xml:lang="en" or xml:lang="de", but certainly not "i-default"... :-)
Like xml:id and similar attributes xml:lang can be used without any
namespace tricks, all XML processors are supposed to know what it is
or ignore it.
> I've always understood xml:lang to describe the contents of the XML
> document itself, whereas <Language> describes the content and
> capabilities of the search engine being referred to.
Yes, you are right, actually you can attach xml:lang to any element,
it then covers all attributes and enclosed elements without another
specific xml:lang. Unrelated to the <Language> element, as you said.
Thanks, Frank