Halliday & Matthiessen (2004: 478):
… needs (nouns of modulation) relate to proposals, which are inherently modulated — eg ‘it is necessary for…to…’. These again have no corresponding mental process verbs; they differ from nouns like order (the name of a verbal process) and insistence (the name of a mental process) in the same way that fact differs from thought and statement — they do not imply a Sayer or a Senser. Like a proposition, a proposal may either be embedded as Qualifier to one of these nouns … or may function on its own as a nominalisation …