getting all the input elements of a form tag

[yawnmoth]

I'm trying to get a list of all the input elements of a form tag and
am having some difficulty doing so.  First, here's my XHTML:

<div>
    <form action="">
    <input type="text" name="a" />
</div>
<div>
    <input type="text" name="b" />
</div>
<div>
    <input type="submit" />
    </form>
</div>

It isn't semantically correct XHTML but that doesn't stop web
developers from coding like that.

Anyway, in both Firefox and IE, if you visit a webpage containing the
above, and hit the Submit button, the resultant URL will have both a
and b defined via GET.

I'd like to be able to get a list of the same input parameters that
the browser does for a given form element.  I had been using "//
form[1]//input" as an XPath query, but that doesn't work, here,
because not all of the inputs are children of the form element.

Any ideas?