Improvement in Schematron implementation (ph-schematron-pure)

[bertrand-lorentz]

Our Central Validation Service (CVS) uses the third-party Java library ph-schematron in its "pure" mode to execute the Schematron files.
This implementation does not use XSLT, and one of the differences with other XSLT-based implementation is the way variable declared in <let> elements are handled: they are (re-)evaluated for each execution of an XPath expression containing a reference to the variable.

This could cause some inconsistencies in specific cases, and have a negative impact on performance with large XML files.

We've recently contributed an improvement to this library, to address this issue: phax/ph-schematron#164
This should become available in a future version 8 of the library.
Once this new version is released, we will be able to take advantage of this in CVS.

I'd like to thank Philip Helger (@phax), the maintainer of ph-schematron, for his great work on this library !