Support for Cooperative Experiments in e-Science: From Scientific Work flows to Knowledge Sharing - Identification of Ligand Binding Site and Protein-Protein Interaction Area - page 148

integrating legacy workflows or components and for coordinating their behavior in
a meta-workflow. The runtime behavior of a legacy work fl ow is modeled as a scenario
and wrapped as an agent called a scenario manager . The scenarios are coupled
through a meta-work fl ow , called a study . At runtime, each study has an administrator
agent (the study manager ), which manages the organization information of scenario
managers . As a runtime infrastructure, the workflow bus provides basic services
for interpreting and scheduling meta-workflows, for orchestrating plugged legacy
workflow engines, for passing and distributing data between workflow engines,
and for supporting user interaction with workflows. From the system level point of
view, features from different systems are then aggregated and integrated as one
meta-system.
In the context of the workflow bus, the interface of a legacy workflow is modeled
as a set of ports, which have a number of properties: read (input) or write (output),
media, type , and access . These properties indicate where the content of the port is
hosted, and the type of the port (abstract types only have access to data references,
while concrete types describe the location where actual data is stored). The workflow
bus provides a schema to specify the interface and other meta-information related to
the legacy workflow, such as access point of the original workflow and its execution
requirements. The description, namely scenario description , can be interpreted by
the scenario manager; at runtime a scenario manager generates the port stubs, and is
able to search for a suitable workflow engine according to the execution require-
ments described in the description (Zhao et al. 2007 ) .
One of the use cases which have motivated the development of the workflow bus
is the MACS lab experiment. As described by the MACS lab PFT, this experiment
is composed of five processes, from which only one has been designed DC analysis
as a Workflow using the WS-VLAM workflow management system. The remaining
processes required features which are not provided by WS-VLAM and thus where
developed using third-party systems. The workflow bus approach was then pro-
posed as a means to coordinate the execution of the entire flow comprising the
MACS lab experiment.
Figure 7.6 shows how the workflows composing the MACS Lab experiment
which are developed in various systems can be executed through the workflow bus:
first, the workflows are wrapped as scenarios, then the scenario manager (scenario 6)
connects them, and allows the intermediate data to be assigned to the appropriate
work fl ow.

7.5.5 The ProxyService

Rapid adoption of the Service Oriented Architecture has led to development of a
huge number of web services which can be accessed remotely to perform
scienti fi c calculations. Bioinformatics is a good example of a scientific field
which has seen an explosion of the number of available web services (Peachey
et al. 2003 ). Web services offer an appealing paradigm for developing scientific