Re: [ubl-dev] Re: [xml-dev] Re: [ubl-dev] UBL 2.0 and Schema Extensibility

["G. Ken Holman" <gkholman@CraneSoftwrights.com>]

At 2006-05-16 17:25 +0100, Fraser Goffin wrote:
>>It has been difficult to illustrate to people who genuinely believe
>>that W3C Schema solves all problems that there are problems for which
>>it is ideally suited and there are problems for which other
>>technologies are absolutely required to be used in its place.
>
>I am *not* in this camp and neither are my immediate colleagues.

Yes, I understand that and you have been supportive of exploring how 
layering can help.

I understood the problem you were having was my problem of getting 
others to understand the need for layering, not that you were having 
the problems of understanding yourself.

As I heard you describe your questions, I find I'm in the same boat 
of people asking me to provide pure W3C Schema solutions when I am 
unable to do so and have it work.

>As you have said many times yourself Ken, structural validation is
>sometimes a pre-requisite to other forms (e.g. schemaTron) that may be
>used in addition, to cover those aspects that are not practically
>possible using schema validation alone. I agree entirely.
>...
>So, back to my original point. It is *not* that I (or others)
>necessarily think that validation by XSD alone will be sufficient,

I know you don't but here are others who do and it is for that 
audience that we need help trying to get them to understand the role 
W3C Schema plays and the roles it does not play.

>its
>just that XSD *does* have a legitimate and useful role to play (even
>if just limited to structural and some content validation) and I don't
>want to deny that opportunity to anyone processing messages that are
>specified by schema that I also subscribe too.

And I agree XSD plays a critical role in the process and, indeed, all 
of the layers are dependent on a successful XSD pass of the instance.

>So, setting processContents = 'lax' as a minimum allows those that
>want to perform at least some level of validation on an otherwise
>opaque part of the message without the need for implementing any other
>checks if they don't want to.

But what if a black-box use of a UBL construct violates UBL ... 
perhaps because the UBL construct has a required child, but that 
isn't needed by the black box that has wrapped its use of UBL in its 
own element (thus being a black box) and it is taking advantage of 
what it needs ... a "lax" validation would interfere with that.

>For those that do have the inclination
>to do more, they haven't lost anything and indeed as you said and now
>I have repeated, the structural validation step may very well in some
>cases be a required pre-step in order to remove the possibilitiy of
>getting 'false positives'.

I think a black box should be totally opaque ... if anyone doesn't 
need the extension then they surely don't need to look inside ... 
otherwise we might get "false negatives".

>Many of the organisations that subscribe to the standards in my
>industry sector are pretty small outfits with little or no IT support.
>They use pre-configured packages that often provide little
>sophistication for processing XML messages beyond the basics. Updating
>these packages can be a costly exercise. So anything they can get 'for
>free' is undoubtedly welcome.

Indeed ... it has long been an objective to provide a rich 
out-of-the-box experience.

. . . . . . . Ken