Understanding Web Services- XML, WSDL, SOAP and UDDI
Page 3
Unlike existing distributed computing systems, Web services are adapted to the Web. The default
network protocol is HTTP. Most existing distributed computing technologies include the
communications protocol as part of their scope. With Web services, the communications protocol
is already there, in the far-flung, worldwide Web.
New applications become possible when everything is Web service enabled. Once the world
becomes Web service enabled, all kinds of new business paradigms, discussion groups, interactive
forums, and publishing models will emerge to take advantage of this new capability.
Software and hardware vendors alike are rushing Web services products to market. The
widespread adoption of the core standards represents a significant breakthrough in the industry.
Applications can truly be built using a combination of components from multiple suppliers.
Specialists are emerging to provide services in the areas of security, transaction coordination, bill
processing, language translation, document transformation, registries and repositories, accounting,
reporting, and specialized calculation. Applications being built anywhere, anytime, on any system
can take advantage of prebuilt components, speeding time to market and reducing cost.
Meanwhile, ebXML, which chartered and maintains a separate course, continues to solve tough
problems for corporate trading partners that are establishing automated supply chain purchasing
and invoicing systems, large electronic document transfers, and business communities sharing
common goals. The rightful heir to EDI, ebXML is providing an easier-to-use, lower-cost
alternative to businesses automating their interactions with other businesses. With ebXML, a
company's internal IT systems are connected to the IT systems of its trading partners,
subcontractors, and business collaborators. The value inherent in these systems is therefore greatly
increased, as they become essentially part of one large IT system, with essential information
flowing freely across corporate boundaries rather than stuck within them.
Considerable overlap exists between the core Web services technologies and ebXML.
Convergence between the two is based on their common adoption of SOAP as the transport and on
the ability of the respective registries to share data. The ebXML specifications include many
qualities-of-service requirements that are not yet included in Web services, such as message
integrity and nonrepudiation, reliable messaging, business process flow, and protocol negotiation.
Further convergence is possible as the core Web services technologies begin to adopt proposals in
these additional technology areas.
Disagreement remains over the best approach to defining these additional technologies in the
context of Web services. Once the core standards are adopted widely, the discussion moves up the
stack to tackle quality-of-service issues. Security, transactions, process flow, and reliable
messaging standards are needed, and some are further along than others.
The power of XML drives Web services technologies in general, whether it's the core standards,
additional technologies, or ebXML. XML finally solves the problem of data independence for
programming languages, middleware systems, and database management systems. Previously,
data types and structures were specific to these types of software, and attempts at common
definitions, such as CORBA IDL, gained limited acceptance. XML is well on its way to becoming
as well established as its sibling, HTML.
The Web services technologies described in this book are all created using applications of XML in
one way or another. XML is not one thing but rather a variety of technologies in itself, covering
instance data as well as typing, structure, and semantic information associated with data. XML not
only describes data independently but also contains useful information for mapping the data into
and out of any software system or programming language.
Web services provide almost unlimited potential. Any program can be mapped to Web services,
and Web services can be mapped to any program. Transformation of data to and from XML is
essential, but XML is flexible enough to accommodate any data type and structure and even to
