Cos-nonambig validation issue

[jensstalder]

Describe the bug
Some parsers are detecting a Cos-nonambig issue on the latest 2.4 schema. This could (depending on implementations) cause systems to opt-out, and not parse the XML.

Cos-nonambig: Gross And Gross (or Elements From Their Substitution Group) Violate "Unique Particle Attribution". During Validation Against This Schema, Ambiguity Would Be Created For Those Two Particles.

Current discussion is on slack: https://qualipool.slack.com/archives/CB28KC4TW/p1636037112000800

[jensstalder]

Tasks

• Find a way to avoid the error, (consider minOccurs="0")
• Add (at least) a .net validator in the pipeline as well for cross-validator-comparisons. more is better 😉

[jensstalder]

Since we are also adding it I guess it would not be inconsistent to also add

• Add a validator for PHP

Since casasoft uses a bit of PHP we could implement that.

There are other major languages as well though: for Example

• Java
• Your favorite language here

They would need to be made from folks that actually know how to implement them. I guess they will become relevant by usage/implementers of the standard.

[merrycoder]

Since we are also adding it I guess it would not be inconsistent to also add

• Add a validator for PHP

Since casasoft uses a bit of PHP we could implement that.

There are other major languages as well though: for Example

• Java
• Your favorite language here

They would need to be made from folks that actually know how to implement them. I guess they will become relevant by usage/implementers of the standard.

• .NET Standard

I can take care of the implementation.