In this paper, we present an approach to derive structured requirements models from textual use case requirements in the form of process diagrams and ontology using methods based on computational linguistics. These proposed requirements models are capable of modeling both structural and behavioral entities present in a use case. We consider a corpus containing 123 actual requirements use cases created by Infosys Ltd. and translated them to process diagrams and ontology. For evaluating the performance of conversion we propose a few metrics and show that on average our linguistic engine mis-identied 2% of actions and missed out only 3% of the actions described in the input text.