Jonathan Robie wrote:
> I wonder how many users are actually eager to learn more than one 
> schema language, and willing to do so for the benefits one language 
> has over another.
>
> I'm guessing this requires a level of sophistication more common on 
> this list (yes, I use multiple schema languages) than in the world as 
> a whole. This doesn't feel like something heading toward mainstream.
I guess it depends on what you consider mainstream. 

Is ODF mainstream?  They have an issue that some of their vocabularies 
use DTDs, others XSD and others use RELAX NG, for example, which is why 
NVDL might be a good fit for them.  But they use RELAX NG for the main 
schema. Governments are progressively requiring ODF for public 
documents. Already I have seen government projects maintained using 
RELAX NG and converted (jing) to XSD on an as-needs basis.

Is OOXML mainstream? It uses NVDL already. But IS29500 supplies both XSD 
and RELAX NG schemas.

Sometimes it seems that "mainstream" is a euphemism for "can generate 
revenue for big iron makers or toolmakers",  and that certainly has its 
place. (SGML died by being to difficult to make a profit out of; 
Schematron and all DSDL would be much more advanced if any users 
contributed development funding.)  But Schematron is considered 
non-mainstream, yet it is used for handling hundreds of millions of 
financial, taxation and insurance files.  This week I went to teach some 
standards-related courses at our national GeoSpatial organization, and 
they use Schematron as part of their standard set of (XSD) schemas. Is 
mining and mapping mainstream?

The trouble is that  Mainstream != Important, or at least, just because 
something is not "mainstream" does not mean that it is not important.

By the end of this year, most of the world's new documents will be in 
formats described by RELAX NG.  For validation, RELAX NG will be the 
mainstream. I think it is the non-validation uses of schemas where XSD 
will retain its glittering crown for the foreseeable future.

Cheers
Rick Jelliffe