How does it work?

First the portal developer specifies the user interface and logic of a job submission portlet in one Extensible Markup Language (XML) file. Using the Rapid system, this XML specification is translated into a new JSR 168-compliant portlet that is then deployed into a portal framework. A domain specialist uses the user interface to configure and submit the task at hand. This transfers control to the computational task manager, which submits the task to a chosen computing resource and monitors the progress of tasks. The portlet can display the results of these tasks when jobs successfully complete and transfer their output data.

The Rapid XML file is the central point from where the portal developer constructs a new Rapid Portlet. The job submission portlet is entirely specified within this one XML file, without the need for any Java programming. A Rapid XML file contains two XML namespaces: The Rapid namespace and the XHTML namespace.

The markup of the user interface is specified using tags from the standard XHTML namespace. This gives a portal developer a wide range of options to design the user interface using familiar tags. For example, a portal developer with basic XHTML knowledge can easily create tables, use different fonts and incorporate images in the Rapid Portlet without the need to learn a new computer language.

The Rapid namespace is defined to manipulate compute jobs, to specify resources and define the logic and structure of the portlet. Using Rapid tags, the portlet can be subdivided into a set of ’pages’. This allows the developer to guide the user through the process of submitting a task. Instead of displaying all available information at once, a small amount of information can be requested of the user at one time. When all required information has been supplied, the user clicks on a button and navigates to a new page, which in turn can ask for more information, request confirmation or display monitoring information.

When a user starts editing a new job, it is initialised with default values specified by the portal developer. It is up to the portal developer to decide which of these values to hide from the end user and which ones are allowed to be edited. This ensures the end user is not burdened with technical details, such as the name of a specific executable or which environment variables to set. Only the functionalities required by the domain-specific application are presented to the domain specialist. The user can enter new values in a number of different ways. It is possible to present a simple text input box or let the user choose between a given number of options using either a list or a set of radiobuttons. Where a task requires handling files, the user can be presented with an intuitive file browser to help select appropriate files from both the local file system and multiple remote file systems.