Under foundational precepts of Grid computing, two important requirements that all Grid application systems should satisfy are to accommodate the dynamic nature of Virtual Organizations (VOs), and to enforce different levels of security among different VOs. For the research described in this paper, we developed two different use-case scenarios addressing the two requirements, and then showed how the requirements can be met by implementing a Grid information retrieval (GIR) system prototype. The dynamic nature of VO applies not only to increasing and decreasing number of users, but also to the dynamically changing requirement of computing power among the different subcomponents that consist in overall system configuration. This implies that a request to increase computing power by a certain subcomponent can be satisfied by other idling subcomponents taking advantage of overall system flexibility.

This paper describes how we implemented a Grid IR system using VO and security mechanisms provided by Globus toolkit 3.0, and shows how GIR system scalability and security can be improved for dynamic VOs. In order to manage different VOs, we implemented VO management service (VOMS), and registered it to Globus as an additional service.