The Internet Encyclopedia (Volume 3)

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WEBSERVICESTODAY 759

Figure 5: The J2EE platform.

Third Generation: Application Server

The observation that many functions were shared and

common among Web services drove the development

toward richer development environments based on the

Java language and Java libraries. A cornerstone of these

environments became J2EE (Java 2 Platform, Enterprise

Edition), which is a Java platform designed for enterprise-

scale computing. Sun Microsystems (together with in-

dustry partners such as IBM) designed J2EE (Figure 5)

to simplify application development for Web services by

decreasing the need for programming through reusable

modular components and by providing standard func-

tions such as session support and database connecti-

vity.

J2EE primarily manifests in a set of libraries used by

application programs performing the various functions.

Web service developers still had to assemble all the pieces,

link them together, connect them to the Web server, and

manage the various configurations. This led to the emer-

gence of software packages that could be deployed eas-

ier on a variety of machines. These packages later be-

came application servers. They significantly reduced the

amount of configuration work during service deployment

such that service developers could spend more time on

business logic and the actual function of the service. Most

application server are based on J2EE technology. Exam-

ples are IBM’s WebSphere suite, BEA’s WebLogic environ-

ment, the Sun ONE Application Framework, and Oracle’s

9 iapplication server. (See Figure 5.)

Fourth Generation: Web Services

Prior generations of Web services mostly focused on end-

users, people accessing services from Web browsers. How-

ever, accessing services from services other than browsers

turned out to be difficult. This circumstance has prevented

the occurrence of Web service aggregation for a long time.

Web service aggregation meant that users would only have

to contact one Web service, and this service then would

resolve the user’s requests with further requests to other

Web services.

HTML is a language defined for rendering and pre-

senting content in Web browsers. It does not allow per se

separating content from presentation information. With

the advent of XML, XML became the language of choice

for Web services for providing interfaces that could not

only be accessed by users through Web browsers but also

by other services. XML is now pervasively being used

in Web services messaging (mainly using SOAP) and for

Web service interface descriptions (WSDL). In regard to

platforms, XML enhancements were added to J2EE and

application servers. The introduction of XML is the major

differentiator between Web services platforms of the third

and the fourth generation in this classification.

A major step toward the service-to-service integration

was the introduction of the UDDI service (see the above

section Web Services Discovery).

Three major platforms for further Web services in-

teraction and integration are: Sun Microsystems’ Sun

ONE (Open Net Environment), IBM WebSphere, and Mi-

crosoft’s .NET.

Sun ONE—Sun’s standards-based software architecture

and platform for building and deploying services on

demand. Sun ONE’s architecture is built around exis-

ting business assets: Data, applications, reports, and

transactions, referred to as the DART model. Major

standards are supported: XML, SOAP, J2EE, UDDI,

LDAP, and ebXML. The architecture is composed of

several product lines: the iPlanet Application Frame-

work (JATO), Sun’s J2EE application framework for

enterprise Web services development, application ser-

ver, portal server, integration server, directory server,

e-commerce components, the Solaris Operating Envi-

ronment, and development tools.

IBM WebSphere—IBM’s platform to build, deploy, and

integrate your e-business, including components such

as foundation and tools, reach and user experience,

business integration, and transaction servers and

tools.

Microsoft .NET—Microsoft’s .NET platform for provid-

ing lead technology for future distributed applications

inherently seen as Web services. With Microsoft .NET,

Web services’ application code is built in discrete units,

XML Web services, which handle a specified set of

tasks. Because standard interfaces based on XML sim-

plify communication among software, XML Web ser-

vices can be linked together into highly specific applica-

tions and experiences. The vision is that the best XML

Web services from any provider around the globe can

be used to create a needed solution quickly and easily.