| In a previous section, we were introduced to the Grid Computing concepts, the new open standard software architecture model (i.e., OGSA), and the new programming model for Grid Computing (i.e., OGSI). The GLOBUS software technology toolkit (Globus GT3) version 3 [1] is the major reference implementation of the OGSI standard. The Globus GT3 software is utilized by a number of worldwide technology initiatives, including utility-based computing, IBM's Business On Demand computing, virtualized resource sharing, and distributed job schedulers . These activities serve as proof of concept of open standard resource sharing and interoperability in Grid Computing. This software and its surrounding architectures are in the process of evolution, and we will therefore concentrate our discussions in this chapter to the recent (very stable) release of the Globus GT3 toolkit. The Globus GT3 toolkit is the most widely utilized and explored infrastructure software for grid middleware development, worldwide, among grid practitioners . Hence, we explore this toolkit in depth. We introduce the Globus GT3 software architecture and the programming model using sample code listings. We divide this discussion on GT3 into three subsequent chapters. First, we discuss the high-level architecture of this toolkit, and in the next chapter we cover the programming model and tools introduced by GT3. Finally, our discussion ends with an implementation sample of a grid service to explain the concepts we have learned in the previous chapters of this book. Also, we devote an entire chapter to discuss the high-level service defined by GT3. Let us now begin to explore the GT3 software architecture. | 