Core
Web Services Today
Editor's note –
Companies seeking to implement Web services often face confusion
over the relationship between ebXML and Web services. David
Webber seeks to clarify that relationship in this article.
David
R. R. Webber
Over the past
several years we have seen the development of a huge array of XML
standards relating to e-business. Over the last six months a
clearer picture has emerged of how these relate together. Along
with this is the clear knowledge from proven deployments of what
foundation capabilities are needed to support effective
e-business solutions.
Particularly, people are seeing the
value inherent in the ebXML specifications and implementations as
they sit squarely into the middle of the Web services world
today, not as a complex superset, but as a tried and proven core
set of Web service components that are complimentary and designed
to provide sensible business functionality. Underpinning the
ebXML components are the base functional sets of SOAP messaging
and WSDL configuration syntax. As W3C specifications these
provide horizontal mechanisms.
For simple point
applications with basic XML payloads these may be adequate but
for reliable messaging the ebXML messaging provides the next
level up for comprehensive interactions between partners. Beyond
that there are the emerging vendor web service specifications and
speciality technologies. Figure
1
shows how this landscape looks today. A glossary
of the terms on the chart
can help decipher the acronyms.
As the Web service
landscape continues to evolve the ability to interoperate between
components is increasingly becoming a key driving factor. The
ebXML specifications provide a benchmark in this area and
mechanisms that were originally proven as part of the ebXML
specifications are now being extended to be general Web service
tools.
An example of this
is the OASIS Content Assembly Mechanism (CAM) specification. This
technology allows implementers to build rule templates that align
legacy and new XML transaction content, and also to leverage
shared registry based metadata definitions. This delivers
interoperable transaction content across web service domains.
Another example is the Business Process Schema Specification
(BPSS) that allows a business-centric view to be built of the
processing requirements, and how this plugs into the
Collaboration Protocol Profile Agreement (CPPA) and with the ebMS
messaging by providing consistent definitions and reference
templates so that the complete step-by-step flow can be agreed
and implemented.
As OASIS now
develops the complimentary BPEL (Business Process Execution
Language) this is benefiting from the model that BPSS provides,
while adding new abilities to implement complex interaction
models and reach new platforms and environments. Figure
2 shows
a matrix of these business functional requirements that the core
web services deliver.
For more details
on these functional requirements and the ability to create a
weighted scorecard of factors that may be important for a
company's deployment needs see the recent white paper on
messaging solutions for e-business available at:
http://www.ebxml.org/ebxml_jmt/#documents
, and in a related discussion in ebXML
Forum.
Summary
This article is
designed to introduce the concepts that subsequently over coming
articles will be studied in more depth -- particularly to show
how ebXML technologies can be combined with a service orientated
model, such as defining a WSDL template for an ebXML Registry
service, and how to use ebMS messaging tools to also interface to
simple SOAP clients.
This article also
shows how ebXML technology is applicable across the specturm of
Web service deployments as a stable reference platform with
components that can deployed with extremely small footprints
(such as discrete Java components) through to comprehensive
enterprise level implementations. We look forward to sharing this
journey and enabling implementers to better exploit the available
ebXML technologies today.
Full
disclosure: the author and ebXML Forum editor have collaborated
on several projects, including a book on ebXML.
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