Enterprise Application Integration (EAI) - Guide to Cloud Computing for Business and Technology Managers - page 95

4.1.1.7 Usability
Usability is defined as the ease of understanding and use for availing a
service. While well-designed and ergonomic software is better accepted by
users, the usability is also affected by familiarity, continuity, and strength of
acquired habits. How can we decide if the Microsoft Windows GUI or the GUI
from Apple Macintosh is better? Objectively, even though it is not possible
to define an absolute standard for usability, there are well-accepted norms,
patterns, and best practices for enhancing usability. There are standards to
evaluate and measure the accessibility and the usability for different user
groups, for example, as defined in Section 508 of the Rehabilitation Act or the
Web Content Accessibility Guidelines from the World Wide Web Consortium
(W3C). However, rules, regulations, and laws change from region to region,
which makes it almost impossible to find one standard for all situations. In
short, while accessibility and usability are critical for the acceptance of appli-
cations, which standards are applicable depends on the context of usage.
4.1.2 Systems Heterogeneity in Enterprises
This problem refers to the fact that in a large enterprise or an inter-enterprise
system consisting of an enterprise and its partners, more than one technol-
ogy is generally used to integrate applications. Therefore, it is literally impos-
sible to impose enterprise-wide standards in this respect.
Various kinds of technological heterogeneity can exist in a large enter-
prise, including the following:
a. Middleware heterogeneity : In a large enterprise, more than one type
of middleware is generally used. The two most common types are
application servers and message-oriented middleware (MOM). In
addition, brand (vendor) heterogeneity requires support for differ-
ent brands of application servers and MOMs.
b. Protocol heterogeneity : This heterogeneity refers to the different trans-
port protocols being used to access the services offered by various
applications. Examples of such protocols include IIOP, JRMP, HTTP,
and HTTPS.
c. Synchrony heterogeneity : There is almost always a need to support
both synchronous and asynchronous interactions between appli-
cations. In addition, there is sometimes a need for callback meth-
ods and publish and subscribe. Therefore, many times a situation
arises where the styles of interaction supported by two applications
that wish to interact do not match. Hence, these applications cannot
interact with each other.
d. Protocol mismatch : Related to the heterogeneity of communication
protocols is the problem that arises when different applications