Thus rather than have the parser "look" to find out that, say, the parent of some N P is an S, we simply relabel the N P as an N P [S] . This viewpoint is even more compelling if one does not intend to smooth the probabilities. For example, consider p(N P → P RN | N P [S]) If we have no intention of backing off this probability to p(N P → P RN | N P ) we can treat N P [S] as an uninterpreted phrasal category and run all of the standard PCFG algorithms without change. The result is a vastly simplified parser. This is exactly what is done by<cite> Klein and Manning (2003)</cite> .