Information Technology Reference
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security policies in caGrid. The security enforcement component as
shown in Figure 7.4 allows users to log into caGrid, obtain a grid
credential from the Authentication Service, store it locally, and use it for
subsequent service invocations for the lifetime of the credential (effec-
tively achieving single sign-on by this means). In addition to this single-
sign-on feature, the security enforcement component also allows cre-
dential delegation such that a service can act on behalf of a user. For
example, the Federated Query Processor (FQP) service can use a
delegated credential from a user, query multiple data services on the
user's behalf, aggregate the results, and forward them back to the user.
ServiceMap. myExperiment is a sister project of Taverna and a
Web-based collaborative platform for sharing workflows and related
research objects such as data items, papers, and software bundles. The
ServiceMap component simply uses myExperiment Web site to publish
the workflows [192] built and used by the caGrid community. These
workflows contain detailed descriptions of what the workflows are set
to achieve and instructions on how to use them, for example, what data
to use as input. They also embed knowledge on how to use individual
services as well as how to orchestrate multiple services into a fully
fledged data pipeline. In the next section, we will give some exemplary
caGrid workflows. A more important feature of ServiceMap (to be
discussed in more detail in Chapter 8) is to provide service composition
assistance such as recommending service(s) and/or operation chain(s)
that are of interest to users.
Several other Taverna extensions for specific uses exist such as
CDK-Taverna [193] and an R-extension [194]. The former is an
extension to access a cheminformatics library called CDK, while the
latter allows users to submit a statistical calculation job to a remote R
server. The caGrid extension of Taverna is implemented from the
perspective of services computing, thereby enabling users to access
a broad range of remote services in a more standard, secure, and
scalable manner. In this way, scientists can greatly improve their
productivity by accessing powerful information provision tools and
automating their data analysis, without knowledge of, or control over,
the internal workings of those tools. In addition to caGrid services, we
have successfully applied the caGrid Workflow Toolkit in other projects
that use the similar service technology stack, for example, the Cardio-
Vascular Research Grid (CVRG).
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