Re: [xml] [RFC] More error message changes

[Matthew Burgess <matthew linuxfromscratch org>]

(with apologies to Kasimier who now has two copies of this - I'll 
remember to "Reply to All" some day!)

Kasimier Buchcik wrote:
>
> Matthew Burgess wrote:
>
>> a) When presented with this, our typical user is unlikely to 
understand what a 'simple type' or 'facet' are, nor would they be able 
to change the affected schema even if they did understand it.
>
> Hmm, if they don't understand the meaning of those schema component
> names, nor can change the affected schema, why do they read it at
> all? :-)

Yeah, I knew someone was going to ask that, but I thought my email was 
getting too long as it was :)   Basically our scenario is this: we have 
folks send us XML files (generated on their behalf by some GUI) which we 
then have to validate before processing.  If the file is invalid, we 
need to give them as much help as possible for them to be able to fix 
their document before resending it.  They don't know what an XML Schema 
is nor what any of the schema terminology means.  Now that I think about 
it, they probably wouldn't even know what XML, 'element' or 'attribute' 
means either - more on that later!

> Additionally thore reports have to be used by both worlds:

> by the people who should not read them, and those who need as much
> information as possible. The latter being me, since I try to implement
> the spec.

OK, consider the message I gave in my OP:

"Element 'elemA', attribute 'attrB': The value '0' is less than the 
minimum value allowed ('1')".

From that, can you not infer what the facet is (minInclusive, although 
arguably it could be maxInclusive too once implemented) and given the 
schema, what the particular type is too?  I might just have simplified 
the test case too much, but by looking at the schema I can obviously see 
 what type attrB of elemA should be, and therefore can figure out 
whether a) the schema is incorrect or b) the instance is incorrect.

> The form of '[xyz]' is used throughout the schema processor, the
> piece of the text behind it writen in a manner that the sentence would
> become not understandable anymore in many cases, withou a [xyz]; try a
> look at all the other reports. Additionally it's mory easy to implement,
> since the [xsz] is autogenerated according to the given schema component
> and node.

OK, I'll admit I am only concerned with the facet stuff for now and 
therefore am probably blinkered in my opinion at the moment.

Hmm, with more thought, I'm not sure this will actually achieve my 
desired goal anyway; that is to let the users know, probably even in 
non-XML terms, why their document isn't going to be processed by us.

Essentially I need the ability to translate what 'xmllint' would tell me 
into something the users can understand (e.g. "Your document had an 
invalid 'age' of 'x', it should be between 'y' and 'z'").  They should 
hopefully then be able to figure out how to change the 'age' using their 
GUI.

Is this what xmlSchemaSetValidErrors() is for?  Does anyone have any 
examples of their own custom callback functions for this that they could 
share with me?

>> 1) Implement messages for MINEXCLUSIVE, MAXEXCLUSIVE, TOTALDIGITS, 
FRACTIONDIGITS and WHITESPACE facets (adding testcases of course :))
>
>
> OK, great!

The patch for this should be ready in the next couple of days.

> The whitespace facet is handled in an other way, it just gives says
> how to normalize a value before it is checked against the primitive type
> and all the other facets.

So, can a user get this wrong in their instance, or is this a schema 
only facet?  From a brief look at the spec, it seems this is very 
unlikely to be overridden/overridable.

Thanks a lot Kasimier.

Regards,

Matt.