Leveraging the Power of the Grid with Opal

Grid systems provide mechanisms for single sign-on, and uniform APIs for job submission and data transfer, in order to allow the coupling of distributed resources in a seamless manner. However, new users face a daunting barrier of entry due to the high cost of deployment and maintenance. They are often required to learn complex concepts relative to Grid infrastructures (credential management, scheduling systems, data staging, etc). To most scientific users, running their applications with minimal changes and yet getting results faster is highly desirable, without having to know much about how the resources are used. Hence, a higher level of abstraction must be provided for the underlying infrastructure to be used effectively. For this purpose, we have developed the Opal toolkit for exposing applications on Grid resources as simple Web services. Opal provides a basic set of Application Programming Interfaces (APIs) that allows users to execute their deployed applications, query job status, and retrieve results. Opal also provides a mechanism to define command-line arguments and automatically generates user interfaces for the Web services dynamically. In addition, Opal services can be hooked up to a Metascheduler such as CSF4 to leverage a distributed set of resources, and accessed via a multitude of interfaces such as Web browsers, rich desktop environments, workflow tools, and command-line clients.