IRI for datatype Markdown

[redmer]

Some IRI's I found:

• http://ns.ontowiki.net/SysOnt/Markdown, a rdfs:Datatype. Used by DBpedia, as well as Eccenca for building widgets' UI.
• xtypes:Document-Markdown, a rdfs:Datatype. Via http://graphite.ecs.soton.ac.uk/xtypes/, that defines many, many more datatypes.
• mime:markdown;charset=utf-8 represents the mimetype from the IANA registry. A skos:Concept.

On different specifications

There is no single Markdown specification, i.a. GitHub Flavored Markdown (GFM), CommonMark.

Should these have seperate identifiers? I tend to think not, as rdf:HTML was originally defined with a valid value space of those strings that were valid according to DOM4, but the DOM specification has since been evolving and I've found no discussion on replacement identifiers for the datatype.

References

Wouter Beek, Filip Ilievski, Jeremy Debattista, Stefan Schlobach & Jan Wielemaker. (2018). "Literally better: Analyzing and
improving the quality of literals". Semantic Web, 9(1), 131-150. https://doi.org/10.3233/SW-17028 (Public copy: https://research.vu.nl/ws/portalfiles/portal/123184040/Literally_better_Analyzing_and_improving_the_quality_of_literals.pdf)