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datasets, for example, it is not practical and may be
impossible to move the data to the system where
the job will actually run. Using data replication
or otherwise copying a subset of the entire dataset
to the target system may provide a solution. If
the Grid resources are geographically distributed
with limited network connection speeds, design
considerations around slow or limited data access
must be taken into account. Security, reliability,
and performance become an issue when moving
data across the Internet. When the data access may
be slow or prevented one has to build the required
logic to handle this situation. To assure that the
data is available at the appropriate location by the
time the job requires it, the user should schedule
the data transfer in advance. One should also be
aware of the number and size of any concurrent
transfers to or from any one resource at the same
time.
Beside the above described main requirements
for applications for running efficiently on a Grid
infrastructure, there are a few more issues which
are discussed in Jacob (2003), such as schedul-
ing, load balancing, Grid broker, inter-process
communication, and portals for easy access, and
non-functional requirements such as performance,
reliability, topology aspects, and consideration of
mixed platform environments.
for scientists without any background in computer
science or Grid computing. Historically, SAGA
was influenced by the work on the GAT Grid
Application Toolkit, a C-based API developed
in the EU-funded project GridLab (GAT, 2005).
The purpose of SAGA is two-fold:
1. Provide a simple API that can be used with
much less effort compared to the interfaces
of existing Grid middleware.
2. Provide a standardized, portable, common
interface for the various Grid middleware
systems.
According to Goodale (2008) SAGA facilitates
rapid prototyping of new Grid applications by al-
lowing developers a means to concisely state very
complex goals using a minimum amount of code.
SAGA provides a simple, POSIX-style API to
the most common Grid functions at a sufficiently
high-level of abstraction so as to be able to be
independent of the diverse and dynamic Grid
environments. The SAGA specification defines
interfaces for the most common grid-programming
functions grouped as a set of functional packages.
Version 1.0 (Goodale, 2008) defines the follow-
ing packages:
•
File package - provides methods for access-
ing local and remote file systems, browsing
directories, moving, copying, and deleting
files, setting access permissions, as well as
zero-copy reading and writing
The Simple API for Grid
Applications (SAGA)
Among the many efforts in the Grid community
to develop tools and standards which simplify the
porting of applications to Grids by enabling the ap-
plication to make easy use of the Grid middleware
services as described above, one of the more pre-
dominant ones is SAGA, a high-level Application
Programmers Interface (API), or programming
abstraction, defined by the Open Grid Forum
(OGF, 2008), an international committee that
coordinates standardization of Grid middleware
and architectures. SAGA intends to simplify the
development of grid-enabled applications, even
•
Replica package - provides methods for
replica management such as browsing
logical file systems, moving, copying, de-
leting logical entries, adding and removing
physical files from a logical file entry, and
search logical files based on attribute sets.
•
Job package - provides methods for de-
scribing, submitting, monitoring, and
controlling local and remote jobs. Many
parts of this package were derived from
the largely adopted DRMAA Distributed
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