New Statistical Algorithms for the Analysis of Mass - FU Berlin, FB MI ...

110 CHAPTER 5. COMPUTER SCIENCE GRID STRATEGIES
2. Pipeline oriented: A large workflow consisting of many different and
dependent tasks is created and for each step different jobs are submitted
to the queue
According to the definition given by Workflow Management Coalition, a
workflow is: “The automation of a business process, in whole or part, during
which documents, information or tasks are passed from one participant to
another for action, according to a set of procedural rules” (WfMC, 2007).
A business process is the set of procedures required for obtaining a given
result, therefore workflow is the automation of a set of operations that allows
obtaining a given result, with the exchange of information among involved
entities and with respect to defined procedural rules. The operations involved
by a workflow are called activities; an activity is a part of the entire work and
it represents a logical step in the process.
Since in the data-oriented case the problem can be reduced to how to split
up the data the pipeline-oriented case is considerably more difficult. Here, the
workflow must be defined, implemented, and executed. This issue of execution
in a given order of complex computational tasks in a Grid environment has
even been discussed by the “Grid Computing Environment Working Group”,
in the Global Grid Forum (Hugh P. Bivens, 2001).
To run a workflow into a Computational Grid it is necessary to define a
language to be interpreted and manipulated automatically from a management
system, which should allow defining a set of activities, their relation,
involved entities (i.e. Applications, data resources, etc.) and some criteria for
determining the start and end of the processes.
However, there are many available workflow manager that fulfill these tasks
(such as Nimrod, Triana, Taverna, Pegasus, Proteus) but they need to be
installed on top of an existing Grid platform and are usually not part of them
(a nice exception is the myGrid project (Stevens et al., 2003)).
5.1.3 Problems of Todays Grid Systems
Nowadays most Grid systems are run by large research organizations, companies
or governmental institutions such as NASA (Information Power Grid),
US Department of Energy together with IBM (Science Grid) or the European
Union (EGEE). These organizations have dedicated staff who set up, configure,
administrate and manage these projects. This is still far away from trivial,
making these administrators vital to the task. As in the case of the Internet
boom in the late 1990’s what is really is needed to fulfill the “everyone can
use the Grid” vision is
� Significantly reduce the complexity of installing and maintaining a Grid
system.
� Provide easy to use client software that can compute jobs on Grid resources.
� Allow for easy participation in a Grid system either as user who wants
to compute a large problem or to provide resources - this includes things
such as registration and security models.
� Merge the needed components such as the Grid platform, workflow manager
and scheduler into some consistent product.
� Allow for easy enabling of Grid technology to existing algorithms.