On core case marking patterns in two Tibeto-Burman languages of Nagaland

The innovative use of an oblique relational morpheme to disambiguate semantic roles or to signal the increased agency of the referent of a core argument can result in the reanalysis of a case marker that is employed in a new, purely abstract function of marking a core grammatical function. The extent to which such marking of a core argument becomes obligatory in the grammar of a language has implications for the development of case alignment patterns.