First the Good News...
The 2020 edition of the ISO Schematron standard has been accepted by ISO/IEC national standards bodies, and is out now. It says: This edition is backwards compatible with ISO/IEC 19757-3:2016, supersedes it and provides extra query language bindings, in particular for XSLT3.
Congratulations to all involved! For me, it is intensely heartening to see that Schematron has enough community momentum that it now doing fine. I (Rick Jelliffe) was the editor of the initial 2006 version and I drafted the next version before having to pull out for personal reasons. This finally appeared as the 2016 version under the editorship of Alex Brown. The 2020 version was put out with the benefit of the excellent Andrew Sales as editor, and without my involvement. Special mention too should be made of Tony Graham, David Maus and the SQF team at OxygenXML for their work in developing resources and a viable community.
It has gone from its original 25 pages to now 39 pages: I dont wan't to fat-shame other standards, but it looks like there is no bloat. Surely it is a sweet spot for this kind of standard that the technology it describes be small enough that it can be implemented by a single developer in a few weeks, all going well!
ISO/IEC Reneges
However, I note with extreme displeasure that ISO/IEC has recently reneged on its policy of making available free PDFs for standards that were brought into ISO from the outside: they want you to buy it. In the case of the 2020 edition, which is some corrections and additional annexes only to the freely-available 2016 edition, it is ridiculous bastardry on ISO's part.
This is an important standard used by many financial and government organizations, such as the German XRechnung initiative, but the core library technologies are almost entirely implemented or maintained by private individuals as open source projects (such as David Maus' SchXslt): these small or not-for-profit developers should not have to abruptly have to fork out US $175 for the 2020 edition which differs only in a few pages from from freely available 2016 edition. It is likely we have reached the point where it would be better to move ISO DSDL out of ISO for development, so it meets the requirements of this betrayal.
The ISO website has the TOC and the non-normative frontmatter including the definitions
at
https://www.iso.org/obp/ui/#iso:std:iso-iec:19757:-3:en
The previous 2016 version is still publicly available for free, at:
http://standards.iso.org/ittf/PubliclyAvailableStandards/c055982_ISO_IEC_19757-3_2016.zip
I will attempt to get the most recent versions of the artifacts (XSD and SCH schemas for Schematron and SVRL) which will be able to be made publicly available. I expect that the QLB for XSLT3 and Xpath3 merely implements some existing implementation (presumably SchXslt) so users
Standards Citation
In the usual run of events, new requirements documents invoking ISO Schematron should
flip to use the 2020 date:
ISO/IEC 19757-3:2020 Information technology — Document Schema Definition Languages
(DSDL) — Part 3: Rule-based validation using Schematron
However, numerous organizations have policies in place to only allow (freely available) open standards. For instance, John Dziurłaj wrote on the Schematronist mail list:
any standard incorporated into the Voluntary Voting Systems Guidelines must be freely available per US Federal Law.Any body which finds itself in this position of needing to make normative reference
should stick with an undated version
ISO/IEC 19757-3 Information technology — Document Schema Definition Languages (DSDL)
— Part 3: Rule-based validation using Schematron
or
ISO/IEC 19757-3:2016* Information technology — Document Schema Definition Languages (DSDL) — Part 3: Rule-based validation using Schematron (*noting corrections of 2020)
or
ISO/IEC 19757-3:2016 Information technology — Document Schema Definition Languages
(DSDL) — Part 3: Rule-based validation using Schematron (normative)
ISO/IEC 19757-3:2020 Information technology — Document Schema Definition Languages
(DSDL) — Part 3: Rule-based validation using Schematron Annex J Query language binding for XSLT3 (non-normative)
Please note that though the text of ISO Schematron 2020 says it "supercedes" previous versions, this merely means that the current version from ISO's POV is the 2020 version: in some standards, where the technology standardized by a new version of the standard is substantially different from the technology of the old, both versions of the standard may continue to be maintained. There is no need to update existing references or to stop using them in future references.
XSLT3 users: Please also note that using a different Query Language Binding from the ones specified in ISO Schematron 2016 does not make the Schematon non-conforming. The standard merely specifies what the standard QLBs are. Using a non-standard QLB with its own identifier does not make a Schematron schema non-conforming.