In 184.108.40.206 “Additional constraints” [#TDTAGCONS] we are told “we need to declare the TEI namespace in Schematron”, and the example demonstrates how:
<sch:ns prefix="tei" uri="http://www.tei-c.org/ns/1.0"/>
But actually putting this declaration (or one for the RELAX NG namespace) results in an invalid ISO Schematron file as these two declarations are automagically inserted by `roma` (and by Roma).
But while we're at it, isn't it a bit weird to require a <constraint> and <constraintSpec> ancestry for a namespace declaration? Maybe <sch:ns> should be allowed as a direct child of <schemaSpec>?