Q:

Dependencies in case phrases

Languages like Japanese are said to have case phrases (KP). I don't understand why case particles are considered heads. Why is the structure of NP+ga [KP [DP x] [K ga]] (ie the DP depends on ga)?

A:

I don't have detailed knowledge of Japanese but in Urdu there are two approaches. One says that the case markers are suffixes, whilst the other assumes that they're particles and posits a KP. A KP in Urdu is something like a PP but it's headed by a case marker (K). In fact, there's a hierarchy: PP>KP>DP>NP.
Note that the categorial head of a phrase needn't be its functional (lexical) head. Functional heads are content words.

