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Distributed Data Repository Supporting Ad-Hoc Collaborations

This paper presents the design and implementation of a distributed data repository for Grid environments that supports secure sharing of possibly confidential data by members of ad-hoc created groups. The system is composed of three independent services metadata service, replica locator service and storage service. The group-based access control is achieved through augmentation of the user credentials required by the back-end storage service using a chain of authorization assertions added by anticipating services. The metadata service introduces a very flexible system for storing and querying the metadata. The metadata schemas define a variable length vector of attributes that can be easily modified by introducing new versions without any intervention of the system administrator. In addition, the user may organize the metadata into a tree hierarchy enabling the creation of custom views of data collections that are independent of the actual organization of the storage.