W3C home > Mailing lists > Public > w3c-sgml-wg@w3.org > April 1997

Re: Error handling in XML

From: Terry Allen <tallen@sonic.net>
Date: Fri, 18 Apr 1997 22:59:27 -0700
Message-Id: <199704190559.WAA27882@bolt.sonic.net>
To: tbray@textuality.com, w3c-sgml-wg@w3.org
Time Bray writes:
| The subject is violations of well-formedness.  Well-formedness should be easy 
| for a document to attain.  In XML, documents will carry a heavy load of 
| semantics and formatting, attached to elements and attributes, probably with 
| significant amounts of indirection.  Can any application hope to 
| accomplish meaningful work in this mode if the document does not even manage 
| to be well-formed!?!?

Please rephrase your questions in formal language.  Documents don't
attain anything, applications don't hope.  

| I suggest that we add language to section 5, "conformance", which says:
| 
|  "An XML processor which encounters a violation of the constraints
|   of well-formedness must not thereafter pass any information about
|   text or markup to the application.  It must pass to the application
|   a notification of the first such violation encountered.  It MAY 
|   thereafter, at user option, pass to the application information
|   about well-formedness violations encountered after the first."

Oh come on.  That would make it be a violation of conformance to output 
information about invalid portions of the instance aside from its
initial fault, including indexing of what text they contain (malformed
or not) and further malformations.  Real world demands will require
that processors not be so dainty.

| [or in English: you gotta tell the app about the first syntax botch you hit; 
|  you're allowed to send the app more error messages, but you're not allowed 
|  to send anything but error messages after you've detected an error]

Who's going to play cop?  And if this were useful, wouldn't it be 
useful only if all parsers encountered the same error first?

If, as the (deleted) prologue to this question implied, you're 
simply trying to avoid anyone making any effort at error recovery,
please give up now, immediately.

| Some might argue that this violates the Internet creed: "Be conservative in 
| what you supply, and liberal in what you accept."  I can live with that: 

No, I think that's not nearly so useful a creed as is supposed.  

| the consequences of the second half of that creed have led to intolerable 
| results in the quality and usability of the data on the Net.  Furthermore, 

Name three such results.

| if you want to serve up ill-formed dogshit, this will presumably remain
| possible, because: "text/html means never having to say you're sorry."

?




Regards, Terry
Received on Saturday, 19 April 1997 01:57:58 EDT

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