| Defining Grid
25 Apr 2003
While still in draft format, the Global Grid Forum attempts
to define an Open Grid Service Architecture Platform.
By Louis Chua
When most people think of a grid, the idea of an interconnected
system for the distribution of electricity or electromagnetic
signals over a wide area, especially a network of high-tension
cables and power stations, comes to mind.
This image is contributing to the growing hype over grid
technology. However, the reality is not quite the same thing.
Ask N number of people what grid is, and you will get at
least N different definitions of grid, declared Karthik Ramarao,
Itanium programme manager, Hewlett-Packard, at the recent
Physical Sciences Virtual Grid Community Symposium 2003.
According
to IBM's definition, "a grid
is a collection of distributed computing resources available
over a local
or wide area network that appear to an end user or application
as one large virtual computing system. The vision is to create
virtual dynamic organisations through secure, co-ordinated
resource sharing among individuals, institutions, and resources.
Grid computing is an approach to distributed computing that
spans not only locations but also organisations, machine
architectures and software boundaries to provide unlimited
power, collaboration and information access to everyone connected
to a grid."
While IT standards usually evolved from the dominant implementations
that came out of a mishmash of various solution from vendors,
grid computing is developing from the other end. Before any
vendor can stake its claim to a dominant position, standards
have already started evolving for grid.
The Open Grid Services Architecture (OGSA) is a proposed
evolution of the current grid technologies towards a grid
system architecture based on an integration of grid and web
services concepts and technologies. Members of Global Grid
Forum (GGF) put OGSA forward to address these challenges.
The GGF is a forum for exchanging information and defining
standards of grid technologies for researchers and industry
players. GGF was formed from the Grid Forum, the eGrid European
Grid Forum, and the Grid community in the Asia Pacific. GGF
concentrates on the Integrated Grid Architecture that can
serve to guide the research, development, and deployment
activities of the emerging grid communities.
The architecture defines uniform semantics for exposed services,
also known as the grid service, by leveraging on concepts
and technologies from the grid and web services communities.
OGSA defines standard mechanisms for creating, naming, and
discovering transient grid service instances as well as providing
location transparency and multiple protocol bindings for
service instances; and supports integration with underlying
native platform facilities. Initial proposed technical specifications
have been developed by the Globus Project and IBM, and are
being put forward at the Global Grid Forum for
discussion, refinement, and eventual standardisation.
There are mainly four main working groups in GGF that are
working on defining grid. Firstly, the Open Grid Services
Architecture Working Group (OGSA-WG) is attempting to define
a platform that specifies the scope of the services, identify
the core set of such services so that specifications can
be created to support the functionality essential for these
core services and their inter-relationships. Secondly, the
Open Grid Services Infrastructure working group (OGSI-WG)
is attempting to define the mechanisms for creating, managing
and exchanging information among grid services. Thirdly,
the Open Grid Service Architecture Security Working Group
(OGSA-SEC-WG) is attempting to incorporate security features
as a integral part of OGSA. The working group provides a
grid security mechanism to ensure that all the communications
between services are secure. And finally, the Database Access
and Integration Services Working Group (DAIS-WG) is attempting
to define the connectors for integration and database access.
With the close technological links between web services
and grid services, it is not hard to position grid as the
next distributed computing concept. According to Gartner,
many businesses will be completely transformed over the next
decade by using grid-enabled web services to integrate across
the Internet to share not only applications, but also computing
power.
Web
services grew out of a need to provide connectivity between
disparate systems. Often, there is
a need to integrate
services across distributed, heterogeneous, to form dynamic "virtual
organisations". This virtual organisation can be formed
from the disparate resources within a single enterprise as
well as from external resource-sharing and service provider
relationships. With information coming in from every possible
direction, integration is a technically challenging task
because of the need to achieve various quality of service
standards when running on top of different native platforms.
The OGSA also defines, in terms of the Web Services Description
Language (WSDL) interfaces and associated conventions, mechanisms
required for creating and composing sophisticated distributed
systems, including lifetime management, change management,
and notification. Service bindings can support reliable invocation,
authentication, authorisation, and delegation, if required.
Fundamentally, OGSA is a service-oriented grid architecture
powered by a grid service, which is a special web service
that provides a set of well-defined interfaces that follow
specific conventions. The interfaces of grid services address
discovery, dynamic service instance creation, life-time management,
notification, and manageability; while the conventions of
grid services address naming and upgrading issues. The standard
interface of a grid service includes multiple bindings and
implementations such as the Java and C# languages. Such grid
services can be deployed on different hosting environments,
even different operating systems.
Web services technologies are designed to support loosely
coupled, coarse-grained dynamic systems. As such, they do
not fully address all needs of the types of distributed systems
that OGSA is defined to support. To close this gap, this
specification defines a set of WSDL extensions, defined using
extensibility elements allowed by the WSDL language, and
conventions on the use of web services.
The extensions are not specific to grid computing, but have
general applicability within web services as a means of structuring
complex and long-lived stateful applications. GGF is also
advocating the adoption of grid standards within the broader
web services standards bodies such as the World Wide Web
Consortium (W3C).
As such, we can see grid computing starting to move out
of being a mere computation grid to be offered as services.
The computation grid is the concept of linking together multiple
computational resources, usually of idling systems, to form
a powerful virtual super computer. One of the most famous
implementations of computational grid is the SETI project
which is trying to link multiple PCs together to search for
extra terrestrial life. Some of the more prominent grid software
that are available for free include the Globus Toolkit and
Sun Microsystems' Grid Engine.
Locally, the National Grid Project Office was set up this
year to promote grid computing within Singapore. Presently
in Singapore, there is only one startup, Atsuma Technology,
which was set up to target the grid market specifically.
Atsuma is a grid computing consultancy firm that deploys
its own portable software technology called ALiCE (Adaptive
and scaLable internet-based Computing Engine) that harnesses
idle computing resources to increase the usable power of
existing system on the network.
Read this article online at http://computerworld.com.sg/pcwsg.nsf/unidlookup/
A8212551CEEB982048256D080010C4D9?opendocument
[Source:
Computerworld Singapore Vol. 9 Issue No. 24, 25 April - 1 May
2003]
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