Carine Bournez (merci, Carine!) drew my attention to a position paper of Karthik Gomadam et al. An extract of the paper that could also be considered as an abstract:
“Reuse and data mediation have led to several proposals for Semantic Web services, leading to the W3C recommendation for the Semantic Annotation of WSDL and XML Schemas. But adding semantics to REST is more challenging than adding semantics to WSDL. Unlike WSDL, REST-based services are often embedded in Web pages written largely in XHTML.”
The authors propose the usage of a small vocabulary plus GRDDL and RDFa, which, combined with the XHTML file containing the reference to the REST service, can provide a proper Semantic description. A simple but powerful use case both for GRDDL and RDFa…
As an aside, the following paragraph, comparing GRDDL and RDFa, is also interesting by itself (thanks to Mark Birbeck for pointing that out in a mail):
“GRDDL’s advantage is that it’s less intrusive than RDFa, and it lets the user embed annotations in whatever way is most convenient to them. RDFa’s advantage is that annotations are self-contained in the HTML page, so the user only needs to create and maintain a single document (GRDDL forces the user to create two documents, the HTML page and the translation document). RDFa also has the advantage of being a standardized microformat, which makes it simpler for a developer to maintain and understand a page created by someone else.”
 K. Gomadam, A. Ranabahu, and A. Sheth, “SA-REST: Semantically enhancing REST services (SWS-XG position paper and discussion draft)”; http://knoesis.wright.edu/research/sss/standards/sa-rest/.