R Haskell, Peter G. Harrison
Non procedural languages do not have system conventions relating to the interface between language, host system and user as part of their definition, but rather added on in ways dependent on the target system running the language implementation. This gives rise to inconsistencies with the semantics of the language. In this paper conventions consistent with the semantics of non procedural languages are devised.
Information from pubs.doc.ic.ac.uk/non-procedural-languages.