Case realization and identity

Languages with case concord sometimes require that at least one case-concord element in the NP be inflected for case, while others may be uninflected. Focusing primarily on Serbo-Croatian, we review some variants of this case realization requirement in different languages and propose a unified account. This analysis makes crucial use of reentrancy (cp. structure-sharing) in attribute-value matrices, a key explanatory tool of Head-Driven Phrase Structure Grammar.