Halliday & Matthiessen (2004: 474-5):
… we also need to take note of ‘attributive’ clauses where the Carrier is realised by a nominal group denoting a person and the Attribute is a nominal group with an embedded fact clause, either ‘possessive’ with a noun as Head (eg idea, notion, inkling [[that…]]) or ‘intensive’ with an adjective as Head of the nominal group (eg sure, certain, aware, cognizant, oblivious (of the fact) [[that…]]; … These ‘personal’ ‘attributive’ clauses are closely agnate with projecting ‘mental’ clauses: they have no idea ~ they don’t know, I’m not sure ~ I don’t know.