Hi Lou,

I think that, whether a strong one or not, there is a "technological 
view" here, namely I recall hitting Schematron errors in the TEI/P5 
build process (the full one including tests, with `make`). So to the 
extent that the test part of the process is in some way integral to the 
processing of TEI sources, it looks like Schematron is considered part 
of the validity requirement.



On 26/03/17 21:06, Lou Burnard wrote:
> When I define my own Schematron constraints and add them into an ODD,
> their effect is always to reduce  the set of documents which will be
> considered valid, by comparison with the set that might be considered
> valid by TEI All, or by a  version of my ODD without those constraints.
> Hence I infer that schematron constraints are always going to be
> restrictions rather than extensions of an existing schema, which means
> (I think) that adding them has no effect on the TEI Conformance of my
> ODD or the documents it validates. Good.
> But what about the constraints which the TEI itself defines ? If a
> document is valid against TEI All but fails some TEI-defined schematron
> constraint is it no longer TEI conformant? The current definition (in
> chap 23 of the Glines) says nothing on the topic. You could argue that
> the object of most (or all?)  TEI-defined schematron constraints is to
> test some semantic constraint otherwise expressed only loosely in the
> prose, and conformance with the TEI semantic model is also a requirement
> for conformance, so a document which fails the schematron test is ipso
> facto non conformant. You could argue that validation with schematron is
> an optional additional extra which shouldn't be required of all TEI
> users, since not all validating software supports it.
> Just wondering if there are any strong views out there ...