Re: silent recovery from errors considered harmful

> I'm using Amaya more and more, so I find it increasingly
> difficult to accept claims such as:
> 
> [[[
> II.7. What is the reason for a very liberal structure enforcement?
> 
> Amaya has to cope with existing Web pages [...]
> 
> ]]]
> 
> -- Amaya FAQ
> http://www.w3.org/Amaya/User/FAQ.html#What
> Wed, 12 Jul 2000 10:02:45 GMT
> 
> 
> It's clear that Amaya doesn't cope with all
> existing Web pages. It crashes more than occasionally.
> That's completely understandable; I don't encourage
> spending development effort trying to make sense
> of erroneous Web pages.

We never said that Amaya cope with all existing Web pages, but it
does with a large number.


> But what I'm really concerned about is:
> 
> "[...] We [...] decided that
> Amaya should try to fix bugs, but without losing
> information."
> 
> Clearly that's impossible. You're losing information
> about the former (possibly illegal/unsupported) syntax
> of the document.

Amaya doesn't loose document contents.


> It's perhaps useful to attempt certain huristic fixes,
> but not without the informed consent of the user.
> 
> I would suggest:
> 
> (a) When you load a document, use an XML processor.
> If you detect a well-formedness error or if you
> detect an element/attribute structure problem:
> 
> 	(a1) display some "bad markup" icon in the UI
> 
> 	(a2) call tidy to clean up the document.
> 
> 	(a3) start over with the results from tidy,
> 	keeping track of the fact that you've tidied the input
> 
> 	(be careful not to loop; the tidied output
> 	might still not be acceptable to Amaya)

Our thinking is to use an XML parser for XHTML documents and to
provide a profile XHTML where each HTML and XHTML document is parsed
with an XML parser. The work is already started.
We let you or other one connects tidy to Amaya.


> (b) if the user starts to edit (i.e. when you set
> the "dirty" flag and, e.g. change the save icon
> from grey to active), if you're working with tidied
> input, prompt the user with a modal dialog ala:
> 
> 	This document had markup errors. Amaya has attempted
> 	to correct the errors, but there is no guarantee
> 	that the corrections are as you intended. You may
> 	want to review the source of the document.
> 
> 		<Cancel edit>    <OK>
> 
> This approach has two benefits:
> (1) users are informed when Amaya changes their documents
> (2) Amaya developers can stop worrying about buggy
> documents, and leave all error recovery issues to tidy.
> 
> If you want to deal with valid HTML 4.0 documents
> (i.e. valid SGML documents) in (a), very well, but
> there are so few of them them that frankly, I wouldn't
> bother if I were you. But since Amaya itself can
> produce valid HTML 4.0, perhaps it's worth supporting
> for a time.
> 
> 
> Also, regarding integrity,
> please re-consider my earlier request to limit
> (to a few minutes or so) the amount of my work that
> Amaya can lose by crashing
> 
> auto-save periodically, not just at crash time
> Dan Connolly (Fri, Mar 10 2000) 
> http://lists.w3.org/Archives/Public/www-amaya/2000JanMar/0282.html
> 
> -- 
> Dan Connolly, W3C http://www.w3.org/People/Connolly/
> 

-- 
     Irene.