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As grid infrastructures mature, an increasing challenge is to provide end-user scientists with intuitive interfaces to computational services, data management capabilities, and visualization tools. The current approach used in a number of cyber-infrastructure projects is to leverage the capabilities of the Mozilla framework to provide rich end-user tools that seamlessly integrate with remote resources such as web/grid services and data repositories.

In this paper we apply rigorous software engineering tools, Data Flow Diagrams or DFDs, to guide the design, implementation, and performance analysis of Topaz, a GridFTP protocol extension to the Firefox browser. GridFTP servers, similar to FTP servers used on the Internet, provide a data repository for files and are optimized for grid use (support for very large file sizes, high-performance data transfer, third-party transfer, integration with Grid Security Infrastructure). Topaz provides users with a familiar and user-friendly interface with which to access arbitrary GridFTP servers by providing upload and download functionalities, as well as by obtaining and managing certificates.

Since it is integrated into the Firefox browser, Topaz introduces an additional layer of abstraction in the communication between client and server. In this paper, we compare upload and download transmission times of our protocol extension with other traditionally used tools such as UberFTP, the globus-url-copy command, an FTP client, and the Secure Copy Protocol (scp) command. DFDs enable us to identify the causes of performance slow-downs in Topaz when transferring small files with respect to grid tools such as UberFTP and the globus-url-copy command. For large files, Topaz performs as well as the traditionally used tools providing, in addition, scientists with a user-friendly interface.