report - Light Reading

SERVICE-ORIENTED ARCHITECTURES: ORCHESTRATING THE OSDE
Eventing means
to subscribe,
receive and
manage events.
to address domain-specific applications
like security, eventing, notifications,
addressing, and others.
In the OSDE, Web services allow us
to define interfaces towards the capabilities
of the different Service Delivery Platforms that can be
re-used across different existing and new services. For example,
instead of creating a new buddy list feature for a new IP
TV service, the existing group list management of the IMS SDP
could be re-used. In this way, the user has a consistent experience,
and services are developed much faster, since the main
effort becomes that of integrating proven components, rather
than the creation and validation of new ones. This type of service
exposure can be achieved by enabling capabilities and applications
with a Web services interface containing the right level
of abstraction and functionality, commonly called a Web Services
Profile.
Orchestration
The reason behind new technologies for service development
is to provide an environment where better services can be developed
with less effort – services that should closely align to user
needs and service provider business requirements. Developing
Web services and exposing functionalities from the different
SDPs is not enough to create new applications. Two Web services-enabled
functionalities cannot start “speaking” to each
other by themselves. We need a way to compose these functionalities
in a logical way, i.e. a definition that matches the business
requirements associated to the service, and which will
make use of the exposed functionalities.
Orchestration
An executable
script describing a
business process
from the
perspective and
under control of a
single entity. It can
be described as a
workflow applied
to Web services
The term orchestration relates to an
executable script describing a business
process from the perspective and
under the control of a single entity. It
can be described as a workflow applied
to Web services.
“Orchestrated services”, as this new
kind of composed application is called,
exploits the exposure functions of the
different SDPs to create a new functionality.
Applied to the OSDE, this
technical approach brings two core values.
First, re-use of capabilities
becomes a common denominator for orchestrated services,
reducing development efforts and time-to-market for new services.
Second, inter-SDP interactions are moved towards an
external layer, reducing dependency, and increasing the flexibility
of our services in a multi-vendor environment.
The Business Process Execution Language (BPEL)
Well-designed Web services expose a coarse-grained interface
to the supported functionality. This basic service orientation
requirement permits the simplification of the language
used to describe how Web services should be composed into
business processes. The Business Process Execution Language
(BPEL) is one such simplified language. It provides primitives
to invoke Web services and process the results using algorithmic
constructions. BPEL is the first workflow-oriented language
to receive wide industry adoption.
For its clients, a BPEL process looks like any other Web service.
When we define a BPEL process, we actually define a new
Web service that is a composite of existing services. This
process of exposing an orchestration as a Web service allows
an existing orchestrated service to be used in a new BPEL
script, achieving real re-usability of deployed services in new
developments.
Service-Oriented Architectures
The exposure of
SDP capabilities in the
form of Web services
brings openness and
interoperability to the
service platform, but
still leaves many impor-
“Web Services Architecture”,
http://www.w3.org/TR/2004/
NOTE-ws-arch-20040211/, W3C
Working Group, Feb 11/2004
tant variables undefined. Service-Oriented Architectures
provide a framework to normalize Web services exposure,
using a set of best practices to achieve a coherent and functional
service-oriented environment.
The W3C Web Services Architecture Working Group defines
SOA as (see insert) “a form of distributed systems architecture
that is typically characterized by the following properties:
• Logical view: The service is an abstracted, logical view
of actual programs, databases, business processes, etc.,
defined in terms of what it does, typically carrying out
a business-level operation.
• Message orientation: The service is formally defined in
terms of the messages exchanged between provider
agents and requester agents, and not the properties of the
agents themselves.
• Description orientation: A service is described by
machine-processable meta data.
• Granularity: Services tend to use a small number of operations
with relatively large and complex messages.
• Network orientation: Services tend to be oriented toward
use over a network, though this is not an absolute
requirement.
• Platform-neutral: Messages are sent in a platform-neutral,
standardized format delivered through the interfaces.”
Although not a new concept, the SOA approach is being
widely adopted in the market. The main differentiator is that
SOA provides, for the first time, a sound model for correlating
business needs to technological solutions. A sound SOA
implementation can bring considerable business benefits to the
organization.
272 - Alcatel Telecommunications Review - 4 th Quarter 2005 www.alcatel.com/atr
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