09-06-2012, 11:38 AM
VWS: Applying virtualization techniques to Web Services
virtualization techniques to Web Services.pdf (Size: 173.82 KB / Downloads: 5)
Introduction
At this moment, we can easily use web services to
integrate different systems, that is, as an enterprise
application integration (EAI) tool. Integration is the main
area where web services are being broadly used, due
fundamentally to the high level of acceptance of the
standards around web services technology.
Nowadays, as web services are not a mature
technology, some problems arise that can result in loss of
control on some critical aspects of applications, such as
QoS, availability, error management, multi-provider etc.
These new problems, which are impossible to obviate,
prevent web services technology from being massively
adopted.
Current Situation
In the basic architecture proposed by the W3C, we can
differentiate three main roles: client, provider and
discovery agency. Two new elements were introduced in
the last revision of the architecture [1]: human beings
representing the client and the provider, referred to as
requester human and provider human, respectively. These
humans are responsible for agreeing on the service’s
semantics and negotiating its description. Eventually, after
reaching an agreement, the provider entity will publish a
WSDL document containing the description of the service,
which will be used by the client entity to perform a bind
process.
Virtualization
The technique we propose, namely virtualization, is based
on grouping one or more web services inside a unique
wrapper, which is then published as a standard web
service. Clients use the new virtual web service as a
standard one, i.e. there is no difference between real and
virtual from the client’s point of view. With virtualization,
some additional logic can be performed out of the client
applications (error management, provider selection, etc.),
and this way the software complexity is radically reduced,
since developers need only to care about business logic.
Wrapping a group of web services has nothing to do
with the well-known web service wrappers, which are
software components used to isolate the communication
layer of the web services (SOAP, HTTP …) from the web
services implementation. The wrapper term is used here to
refer to a virtual view of a set of web services, so that
clients have a unique view of that group. The virtual view
is in fact published as a standard WSDL document.
Implementing Virtualization
Virtualization will guide us to the use of a new kind of
services: virtual web services (VWS). Any application that
is capable of using a standard web service can be bound to
a virtual web service. Conversely, any provider
component that can be exposed as a standard web service
can also be published as a virtual web service. Our
virtualization technology provides an XML-based
definition language, called VWSDL (VWS Definition
Language), for writing VWSDL documents.