So, WSRF sure seems pretty cool and exciting, huh? However, if you've already programmed Grid-based applications, you're probably thinking that this is all very nice, but hardly enough for The Grid. Remember that WSRF is only a small (but important!) part of the whole GT4 Architecture: it is the infrastructure on top of which most of the toolkit is built. Besides the WSRF implementation, the toolkit includes a lot of components which we can use to program Grid applications.
The Globus Toolkit 4 is composed of several software components. As shown in the following figure, these components are divided into five categories: Security, Data Management, Execution Management, Information Services, and the Common Runtime. Notice how, despite the fact that GT4 focuses on Web services, the toolkit also includes components which are not implemented on top of Web services. For example, the GridFTP component uses a non-WS protocol which started as an ad hoc Globus protocol, but later became a GGF specification.
As mentioned in the preface, the tutorial currently focuses only on the Java WS Core component. Once again, it is important to realize that the Globus Toolkit includes a lot of other components which can help us build Grid systems. Even so, the Java WS Core component is specially interesting because it is the base for most of the WS components. Note that we do not need to have in-depth knowledge about Java WS Core to use many GT4 components like GRAM, MDS, etc. However, if we want to build a Grid system that integrates all of these components with our own services, we will need to know about Java WS Core to actually "glue" all those services together and to program our own services.
Let's take a quick look at what we can find in each of the five families of GT4 component. For more detailed descriptions, please refer to the official Globus documentation or to the Globus Primer (you can find a link in the preface)
The Common Runtime components provide a set of fundamental libraries and tools which are needed to build both WS and non-WS services.
Using the Security components, based on the Grid Security Infrastructure (GSI), we can make sure that our communications are secure.
These components will allow us to manage large sets of data in our virtual organization.
The Information Services, more commonly referred to as the Monitoring and Discovery Services (MDS), includes a set of components to discover and monitor resources in a virtual organization. Note that GT4 also includes a non-WS version of MDS (MDS2) for legacy purposes. This component is deprecated and will surely disappear in future releases of the toolkit.