Abstract-In reality, we often find that proven and workable software, exist without source code. Identifying end-to-end interaction within existing legacy runtime code is a promising way for requirements recovery. Those identified interaction forms a set of use cases. Based on use case modeling concept, ontology is created for each finding interaction in order to check for completeness and consistency. OWL serves as platform for ontology development. That ontology reflects the recovered requirements. The procedures to identify the end-to-end interaction has been formulated and tested for university information systems. R3ST, tighly couple to Proté gé , has been developed with the objective to assist and automate those procedures.Index Terms-End-to-end interaction, use case, ontology, requirements recovery, software comprehension, software maintenance.