Abstract
This paper presents work from a dissertation. In first section, classification of Urdu case-markers and post-positions based on difference of modeling requirement is presented. In second section, the data and analysis to show that the role of instrumental case marker sey is quite diverse and it adopts various thematic roles in the argument structure of verbs. The marker sey marks subjects, objects, instruments, time and space nouns, post-positional phrases, adverbial phrases, etc. The analysis presented shows that semantic considerations about nouns simplify classification of these roles. In third section, it is shown that the marker sey is used to mark indirect subjects for Urdu causative verbs form 2. If indirect subjects really exist, they result in Urdu tetravalent causative verbs. This paper assumes this notion and makes use of semantic case marking for their argument mapping.