Web Service Architectures
With Web Services, information sources become components that you can use, re-use, mix, and match to enhance Internet
and intranet applications ranging from a simple currency converter, stock quotes, or dictionary to an integrated, portalbased
travel planner, procurement workflow system, or consolidated purchase processes across multiple sites. Each is built
upon an architecture that is presented in this paper as an illustrated stack of layers, or a narrative format.
Each vendor, standards organization, or marketing research firm defines Web Services in a slightly different way. Gartner,
for instance, defines Web Services as "loosely coupled software components that interact with one another dynamically via
standard Internet technologies." Forrester Research takes a more open approach to Web Services as "automated connections
between people, systems and applications that expose elements of business functionality as a software service and create
new business value."
For these reasons, the architecture of a Web Services stack varies from one organization to another. The number and complexity
of layers for the stack depend on the organization. Each stack requires Web Services interfaces to get a Web Services
client to speak to an Application Server, or Middleware component, such as Common Object Request Broker Architecture
(CORBA), Java 2 Enterprise Edition (J2EE), or .NET. To enable the interface, you need Simple Object Access Protocol
(SOAP), SOAP with Attachments (SwA), and Java Remote Method Invocation (RMI) among other Internet protocols.
Although we have a variety of Web Services architectures, Web Services, at a basic level, can be considered a universal
client/server architecture that allows disparate systems to communicate with each other without using proprietary client
libraries, according to the WebMethods whitepaper, Implementing Enterprise WebServices with the WebMethods
Integration Platform (December 2001). The whitepaper points out that "this [architecture] simplifies the development
process typically associated with client/server applications by effectively eliminating code dependencies between client and
server" and "the server interface information is disclosed to the client via a configuration file encoded in a standard format
(e.g.WSDL)." Doing so allows the server to publish a single file for all target client platforms.
For the purposes of this paper, we present the architecture stacks starting with the most simple, proceed to the more complex
ones, and then compare them. After this, we will cover other architecture types from Microsoft, Sun ONE, Oracle,
Hewlett-Packard, BEA Systems, and Borland.
Based on initial findings or the current state of implementations, IBM's architecture is most acceptable. All architectures
will eventually come into one umbrella, as there is a risk that if companies go away and keep on building their own extensions
to the basic architecture stack, the promise of Web Services could be lost. The IBM versions, current and future, could
serve as an industry-wide Standard Stack model, after W3C accepts new standards resulting from, for example, the convergence
of IBM WSFL and Microsoft XLANG on workflow processes.
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