Page 98 -

74 Chapter 3 • Enterprise Systems Architecture

modules from any Internet-enabled device (e.g., a Web browser running on a PC or a cell phone)
that uses such standard Internet technologies as HTML, XML, and HTTP(S), which can
access and execute ERP applications. The benefit of the server-centric architecture is that there is
no complex, expensive client software installation. The Internet client device accessing
the Internet architecture already has all the software and configuration it needs. No additional
software need be installed on the client for interaction with ERP applications (i.e., no Java
applets, Windows DLLs, or browser plug-ins are needed). Simple, open architecture creates
easy, inexpensive access and is a big reason why the Web has been such an enormous, fast-
growing success.
On the other hand, the client-centric architecture requires the applications and data to
be downloaded from a server and executed from a client workstation. Each architecture has
its benefits and drawbacks. Although the server-centric architecture has better security
and controls because all the applications and data are on the server and clients do not need
any specific configuration, it does tend to have slower response time because all user requests
are processed on the server. The client-centric architecture similarly has better response time
because user requests are mostly processed on the client’s computer; however, they can
lack security and require all client workstations to be set up according to the standard
specifications.
In addition to improving end-user access, Internet-based architectures also allow better
system-to-system integration, which is often considerably more complicated and costly. The
Web system platform fundamentally supports a better and more open flow of information
between systems. By leveraging such ubiquitous Internet technologies as extensible markup
language and hypertext transfer protocol, the ERP system is able to support better systems
integration. These integration technologies streamline integration of ERP modules with other
organizational applications, custom internal systems, e-Merchants, and customer trading partner
systems. This functionality is supported through the following Web technologies:

•Application messaging
•Component interfaces
•Business interlinks
•Application engine

Service-Oriented Architectures
Service-oriented architectures represents object-oriented architectures for Web platforms.
The first service-oriented architecture for many people in the past was with the use of
distributed component object model (DCOM), an extension of the component object model
that was introduced in 1996 on Microsoft Windows platform. A service is a function that is
well defined, self-contained, and does not depend on the context or state of other services.
A service-oriented architecture is essentially a collection of services. From an ERP
perspective SOA decomposes the business tier into smaller, distinct units of services. These
services collectively support an ERP functional module. They can individually be distributed
anywhere in the system; however, SOA encourages these services to comply with certain design
principles like existing autonomously, yet to evolve independently from each other. SOA basically
produces an application environment with unique characteristics and benefits.
Although SOA is not new, it does go beyond sharing basic data and methods to sharing
business logic and other advanced services. In addition, object-oriented architectures of the past
allowed interactions only within the corporate firewall. SOA allows message interaction between