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rithms can be broken down into their constituent
elements, and programmers can take advantage
of prewritten software modules within Triana to
aid in the development of new algorithms. This
allows the user to bypass the conventional ap-
proach to programming, creating various methods
and coding a core program to connect the set of
related method procedures together.
implement this functionality. The GAT may be
referred to as upperware, which distinguishes
it from middleware (which provides the actual
implementation of the underlying functionality).
Until recently, application developers typically
interact with the middleware directly. However it
is becoming increasingly apparent that this transi-
tion from one type of middleware to another is
not a trivial one. Using interfaces like the GAT,
migrating from one middleware environment is
easier and typically achieved by setting an envi-
ronment variable. The GAT is currently being
standardized through the SAGA working group
efforts within the OGF consortium.
The Grid Application Prototype Interface
(GAP interface) is a generic application interface
that provides P2P-based discovery and com-
munication mechanisms. It is also middleware
independent and defines common high-level
capabilities with bindings provided for differ-
ent service-oriented middleware, such as P2P
middleware for example, JXTA and P2P, and
also middleware for interacting with Web and
Grid services, as illustrated in Figure 4. The GAP
interface hides many of the complexities of deal-
ing with the various environments and provides
a uniform view of how to deploy, discover, and
communicate with distributed services. Specific
details for each environment are typically set us-
ing a configuration file (or GUI in Triana). Such
details can include attributes such as: specifying
which transport protocols to use; providing rules
for specifying Rendezvous peers; or naming
which UDDI servers to use. The GAP massively
simplifies the implementation for an application
as it provides a clean dividing line between simple
distributed interactions, such as discovery and
communication, and low-level details that are
middleware dependent. This allows the applica-
tion developer to develop switchable interfaces
that interact with the underlying middleware in
a coherent fashion but then also allow the flex-
ibility of being to add tools for manipulating
the behavior environments that they run within.
distributing triana taskgraphs
Triana is capable of working within P2P environ-
ments through the use of P2PS and JXTA and it
can work within Grid environments through the
use of the Globus toolkit accessed via the GAT
interface. Further, it has the capability of fusing
these environments through the use of WSPeer
(Harrison & Taylor, 2005), which can host Web
Services and OGSA implementations, such as
WS-RF, within P2P environments like P2PS.
the triana underlying toolkits
Triana builds on distributing systems technolo-
gies by integrating the Grid Application Toolkit
(GAT) (Allen et al., 2003) and its peer-to-peer
subset, called the GAP (Taylor et al. 2003), which
is illustrated in Figure 4. These interfaces provide
application-level capabilities for a number of dif-
ferent types of middleware. So, for example, within
a Grid computing scenario, Triana could use the
GAT's Globus GRAM (Grid Resource Alloca-
tion Manager) binding to execute applications on
distributed resources or similarly it could use the
GAP's JXTA or P2PS (Wang, 2005) discovery and
pipe mechanisms to discover and communicate
with peers in a P2P environment.
The GAT interface provides a generalized
collection of calls to shield Grid applications
from the implementation details of the underly-
ing Grid middleware, and was developed in the
European GridLab Project. The GAT utilizes
adaptors that provide specific bindings from the
GAT interface to underlying mechanisms that
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