According to the RDF 1.1 specification (3.3 Literals), RDF literals are Unicode strings, which should be in Normal Form C (NFC). In NIF, we will follow this recommendation in general. There are, however, circumstances which require the use of Normal Form D (NFD) or even NFKC or NFKD. Therefore NIF allows NFD, NFKC and NFKD, if the use case justifies the usage.
One such use case is, if a linguistic annotator has the requirement to annotate individual diacritics or parts of precomposed characters and syllables. For linguists with this use case or applicable languages, using NFD is obvious and well-justified. We will only give examples here and refer the interested reader to these three documents: Gernot Katzer's page about the Korean Writing system, Wikipedia article about the Korean Hangul, Unicode Normal Form specification.