Cloud Computing and SOA Convergence in Your Enterprise: A Step ...

72 Chapter 4 Making the Business Case for Clouds
computing provider could suddenly discontinue service. There are cost/benefit
trade-offs to be consider here, so make sure you dial both the upside and the
downside risks into your business case.
Agility and Reuse
Agility and reuse are part of the value of cloud computing, and each has its
own benefit to enterprise architecture. First is the ability to save development
dollars through reuse of services and applications. (We talk about services in
Chapter 6, “Working from Your Services to the Clouds.” For now, it is helpful
to note that many services make up an application instance.) These services
may have been built inside or outside of the company, and the more services
that are reusable from system to system, the more ROI is realized from our
SOA using cloud computing.
Second is the ability to change the IT infrastructure faster to adapt to the
changing needs of the business, such as market downturns, or the introduction
of a key product to capture a changing market. This, of course, provides
a strategic advantage and gives the business a better chance of long-term survival.
Many enterprises are plagued these days with having IT infrastructures
that are so poorly planned and fragile that they hurt the business by not providing
the required degree of agility.
Under the concept of reuse are a few things we must determine to better
define the value:
The number of services that are reusable
Complexity of the services
The degree of reuse from system to system
The number of reusable services is the actual number of new services
created, or existing services abstracted, that are potentially reusable from system
to system. The complexity of the services is the number of functions or
object points that make up the service. We use traditional functions or object
points as a common means of expressing complexity in terms of the types of
behaviors the service offers. Finally, the degree of reuse from system to system
is the number of times you actually reuse the services. We look at this
number as a percentage.
Just because we abstract existing systems as services or create services
from scratch, that does not mean that they have value until they are reused
by another system. In order to determine their value, we must first determine