Schema validation Report Language?

["Frank Steimke" <f-steimke@berger-und-steimke.de>]

Hi,
validation of XML-based business documents is often a process with two ore more phases:
a) check structure against XSD or RELAX NG Schema;
b) check additional constraints against Schematron

In typical scenarios the user would like to inspect validation results before he decides about further processing. In order to support automatic inspection as well as logging the incoming trafic, we would like to have the validation report to be a single XML document, which combines all the neccessary information from the validations that took place. We also would like to have extension points for additional, user specific validation, for example electronic signatures or certificates.

So my question to this list is: is there any generic Schema Validation Report Language out there which can act as Schema for reports in this scenario? I'm quite aware of the Schematron Validation Report Language (Annex D of ISO/IEC 19757-3:2016), but this is restricted to Schematron.

Closely related to this question is another one: is it a requirement for every W3C Schema validation engine to report schema errors and validation failures in terms of appendix C "Outcome Tabulations" of XML Schema Part 1: Structures, together with a error location in a standardized way? Does this also hold for relax NG engines (although i know only one ...).

Thanks in advance,
Frank Steimke