Integration Technologies - Guide to Cloud Computing for Business and Technology Managers - page 127

ORB products may choose different scenarios as to how and where to
implement their functionality. They can move some functions to the client
and server components, or they can provide them as a separate process or
integrate them into the operating system kernel.
There are three major standards of ORBs:
1. OMG CORBA ORB compliant
2. Java RMI and RMI-IIOP (Internet Inter-ORB Protocol)
3. Microsoft COM/DCOM/COM+/.NET Remoting/WCF
There are many ORB products compliant with the CORBA ORB specifica-
tions and various implementations of RMI and RMI-IIOP. Particularly, RMI-
IIOP is important, because it uses the same protocol for communication
between components as the CORBA ORB, namely, the IIOP. This makes RMI-
IIOP (Internet Inter-ORB Protocol) interoperable with CORBA.
5.9 Application Servers
Application servers handle all or the majority of interactions between the
client tier and the data persistence tier. They provide a collection of already
mentioned middleware services, together with the concept of a manage-
ment environment in which we deploy business logic components—the con-
tainer. In the majority of application servers, we can find support for Web
Services, ORBs, MOM, transaction management, security, load balancing,
and resource management. Application servers provide a comprehensive
solution to enterprise information needs. They are also an excellent plat-
form for integration. Today, vendors often position their application serv-
ers as integration engines or specialize their common purpose application
servers by adding additional functionality, like connections to back-end and
legacy systems, and position their products as integration servers. Although
such servers can considerably ease the configuration of different middleware
products, it is still worth thinking of what is underneath.
Whether used for integration or new application development, application
servers are software platforms. A software platform is a combination of soft-
ware technologies necessary to run applications. In this sense, application
servers, or more precisely the software platforms that they support, define
the infrastructure of all applications developed and executed on them.
Application servers can implement some custom platform, making them the
proprietary solution of a specific vendor (these are sometimes referred to as
proprietary frameworks). Such application servers are more and more rare.
On the other hand, application servers can support a standardized, open,
and generally accepted platform, such as Java Enterprise Edition.