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Re: XHTML Validator Gives Inconsistent Results

From: John Moran <john@gadgetbuilder.com>
Date: Fri, 3 Jun 2022 11:57:21 -0400
Message-ID: <ce191650-5562-8a8b-6113-3c353b344749@gadgetbuilder.com>
To: www-validator@w3.org
Further information on the XHTML validator providing inconsistent results.

I have found a simple way to reproduce the failure by changing 1 
character in a valid XHTML file:

Validate by URI an XHTML file which includes an <h1> ... </h1>  near the 
beginning.  Change this to <h2> ... </h1>,  an obvious error.   Use the 
back button and validate via "Check" again and it will pass - although 
it now has an error.    Use the back button, click "Show Source" and 
then click "Check" and it will fail (i.e. it will read the actual 
site).  Use the back button and deselect "Show Source" and click "Check" 
and it will pass. You can now go back and it will pass or fail depending 
on whether "Show Source" is on when you click "Check".  If you fix the 
problem at the site, you can still go back and forth with the same 
result reported, i.e. it fails and "Show Source" displays the old source 
with the error even though the fix is on the site and is visibly working 
on the site.

The validator seems to read its cache rather than retrieving the target 
site.  The interesting thing is it takes over an hour for "Check" to 
recover.  I have tried clearing Firefox cache prior to clicking "Check" 
and that has no effect on this issue.

A similar effect occurs with "Revalidate"  - it also can get into this 
situation although it seems to use a different cache which persists for 
longer, more than an hour.

This isn't a problem if you "Check", fix *all* the errors and 
"Revalidate".  But if it takes several tries to fix all the errors then 
it's easy to get locked out of the validator for that page, other pages 
can still be validated.

The example error given can sometimes cause hundreds of erroneous errors 
to be reported due to 1 wrong character so it is difficult to proceed 
without correcting that error and validating again - and if there are 
multiple actual errors it is easy to get locked out of  validating that 
page for hours.  For example, I got 118 errors by changing that single 
character on this page:

Regards,  John
Received on Friday, 3 June 2022 16:04:53 UTC

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