1 Messaging in Web Service Grid with Applications to Geographical Information Systems Geoffrey Fox, Shrideep Pallickara, Galip Aydin and Marlon Pierce (gcf, spallick, gaydin, marpierc)@indiana.edu Community Grids Lab, Indiana University 1. Introduction As standards such as SOAP 1.2, WSDL 2.0, and WS-Addressing become widely implemented and deployed, the initial concepts and implementations of Web Services as “remote procedure calls for the Web” are giving way to a more message-oriented, service-oriented approach. Such systems place an emphasis on managing secure, reliable messages that may be delivered in any number of ways across multiple routing SOAP intermediaries. As we discuss in this article, all communications in SOA-based systems are messages. Further, a powerful way to implement these systems is to place the service “islands” on a software-level messaging substrate that implements efficient routing, security, reliability and other qualities of service. As we will show, such systems support messages of all types, from infrequent update notification events to continuous streams. We suggest that in the complex evolving technology scene today, not only services but their collection into systems of higher functionality should be as decoupled as possible in architecture and tight timing constraints. This we call the principle of building “Grids of Grids of Simple Services” Many important Grid applications in real-time data mining involve all of these message types. We discuss a GIS (Geographical Information System) example from our SERVOGrid (Solid earth Research Virtual Observatory) work that uses the NaradaBrokering messaging system for managing data streams from GPS stations. We are in the process of connecting these to RDAHMM, a time series data analysis program useful for mode change detection. These streaming services form one sub-Grid in the “Grid of Grids” system supporting solid earth science and also containing (sub)-Grids involving code execution services and information/metadata services. 2. Service Oriented Architectures for Grids With the advent of the Open Grid Computing Architecture (OGSA) [1] and the UK e-Science program, Grid computing has aligned itself with Web Service standards activities: Grid infrastructure will be Web Service infrastructure, although the aggressiveness in developing and adopting extensions is a matter of debate. The current general consensus is that Web and Grid Services should follow Service Oriented Architecture (SOA) principles, such as discussed by the World Wide Web Consortium’s Web Service Architecture working group. We summarize key SOA features as follows, following Ref. [2]: 1. SOAs are composed of services that present programmatic access to resources to remote client applications. Typical basic (atomic) services include data access (logically wrapping storage technologies such as databases and file systems) and the ability to run and manage remote applications. More complicated services may be composed of these basic services using workflow expression languages coupled with workflow engines. 2. Services communicate using messages. Messages are usually encoded using SOAP [26]. The asynchronous nature of messaging is one of the keys to Grid and Web Service scalability beyond the intranets. 3. SOAs are metadata rich. We must describe service interfaces, provide descriptions of services so that we know how to use them, provide look-up registries to find service URLs, and so forth. Much debate has gone into refining concepts such as stateful conversations and stateful resources accessed through services [3]. However, we believe that the other two characteristics, messaging and