usecase: describing scientific datasets where the formats are relatively obscure (but still known within their community). URLs to well known READMEs are often the best thing out there - how to express these in schema.org.
For domains such as life sciences, there are resources such as BioSharing.org, which compile information about the standards (formats, ontologies, minimum information guidelines) used by different communities.
Vocabularies such as DCTerms have the notion of conformance to standards (e.g formats) - see http://purl.org/dc/terms/conformsTo.
An approach like this has been used in HCLS dataset description and the bioCADDIE DATS model (Github repo: https://github.com/biocaddie/WG3-MetadataSpecifications).
See also #1155 ?
Amended fileFormat to allow URL when format is unregistered or niche.