IRIs (Chapter 7.3, Element names and URIs)

[RiittaA]

• In our system, we are using IRIs as it is the basis of all the primary LD standards - and upcoming (RDF-star, SPARQL-star), also HTML5
• Support for Unicode is de facto expected for all modern systems.
• We recognize the HTTP request limitation of having to percent-encode IRIs to URIs, that punycoded domains further complicate things, and that displayed IRIs can be used in homonym attacks. These are however things that we cannot escape when operating in a larger environment of linked data. Thus, we see no harm in minting IRIs, as per our experience most IRIs are URIs anyway and in cases where Unicode glyphs are needed, there are good justifications (e.g. utilising the set of glyphs in European languages).
• When minting, we can ensure that no collisions with percent-encoded versions can occur, and that only a well-defined subset of Unicode is allowed (there is no good reason to allow all of the Unicode glyphs allowed in e.g. NCNames).

[csnyulas]

This is related to the similar issue #21, where we explained why we decided to stick with URIs instead of IRIs. In the context of that issue, we have also added specific explanations regarding this to the Style Guide (see CMC-R3, CMC-R4, GC-R4].

I would point out a particular paragraph in the CMC-R3 recommendation: "Internationalisation, if required, should be provided through the use of the UML Element Tags to specify labels that will be used for generation of specification documents in languages other than English. Country specific data specifications, which are meant to be used primarily at a national level, might decide to relax on this convention and permit the use of Unicode characters in the Element names, which will result in the generations of IRIs, instead of URIs [iri]. However, this is unnecessary, and strongly discouraged, in the SEMIC context."

As you mentioned @RiittaA, there are ways to convert IRIs to valid URIs e.g. by percent-encoding Unicode glyphs. So, even in the context of a national-level vocabularies/APs one could adhere to this recommendation, if they want to, by adjusting the tooling, and still keeping the more meaningful names in their conceptual model.