PROPOSAL: 

 * Make users aware of it  when the validator's generator 
   exemption steps in.

 * The info - or warning - message should:

   a) say roughly this: 
      "Exemption: img-s not checked for alt attribute usage because
      a software package was used to generate the document".

   b) include a link to the spec's #meta-generator definition and
      may be also to spec's #guidance-for-conformance-checkers
       
   c) recommend what to do in order to obtain info about the
      page's alternative text usage - such as
         i) offer to re-validate as if the generator string was
            not present (if the validator could be programmed
            to do that) or explain how to remove the generator
            string
        ii) recommend (or offer to run) an additional image check,
            including but not limted to the image report of the
            NU-validator.

BACKGROUND:

CURRENT SITUATION:
* Silent validator = well known signal that document is error free
* Image validation has always been part of HTML validation service

THEREFORE:
   A user of W3's HTML5-conformance checking service deserves
   to be informed when IMG elements have been exempted from 
   @alt text conformance checking (due to the Generator string).

BUT ON THE OTHER HAND: Information must be careful.
* We should avoid that the information about the generator
  exemption leads the author or the tool user to take the 
  validation shortcuts which the generator exception seeks
  to prevent
* But yet also encourage authoring tools to improve - the
   "threat" that the validator user could run a extra validation
   will provide such encouragement to tool vendorers.