B2B Integration : A Practical Guide to Collaborative E-commerce

y """X,
./ \ Request
I Client J^^^^^^T
\ J ' w ~~ Response
Integration Patterns 75
1 Server
Figure 3.20. — Synchronous communication (Request/Response)
as TP monitors, distributed objects and message oriented middleware
(MOM).
A2A integration requires integration of new technology with the old,
realizing a common architecture where all business-enabling applications
are able to communicate with each other. It enables companies to
connect and coordinate data and events among multiple, crossorganization
applications.
Application oriented integration is primarily synchronous in nature,
i.e., it is based on request/reply interactions between the client (requesting
program) and the server (responding program) (see Figure 3.20). Thus,
the middleware supporting this integration pattern has to provide adapters
and an adapter toolkit, to develop custom adapters that support
synchronous program invocation.
In this section, we will discuss APIs and RPCs. The discussion on
different technologies such as CORBA, RMI and TP monitors is provided
in the chapter on middleware technologies.
3.4.1. Application Programming Interfaces (APIs)
An application programming interface is a group of functions or methods
defined by programs, which external programs can invoke to interact
(select information, update information, control the state or notify the
events) with the underlying applications. Just as a keyboard is the
interface for a computer, an API is the software interface for applications,
programs and operating systems. An invocation of each method of an
API is supposed to generate a desired outcome. APIs encapsulate the