Technique H45 procedure description incomplete

H45 is described as

Procedure

 1.  Check that a longdesc attribute exists.

 2.  Check that the link in the longdesc attribute is valid

 3.  Check that the long description describes the original non-text content associated with it.

Expected Results

 *   #1 through #3 are all true

But a) it doesn't explain on what elements we are to check for the longdesc attribute - presumably it should be IMG elements only in this case, and not FRAMES and IFRAMEs

b) surely it's not implying that to pass H45 every element that supports longdesc attributes must in fact do so??  That would cause virtually every page on the web to fail immediately, as I don't think I've ever seen a commercial site using LONGDESC - at least, not correctly.

c) what is meant by valid?  That it's a valid url?  Or it actually points to a resource that really exists?  If the former, fine (and a very good idea, seeing I've seen quite a few cases where the LONGDESC attribute actually contains the descriptive text in the value, rather than a URL pointing to where to find the text), but if the latter, then testing this automatically becomes potentially expensive on a large site (well, it would, if anyone actually used LONGDESC).