Cloudware Technologies - Guide to Cloud Computing for Business and Technology Managers - page 317

in achieving service consistency across departmental boundaries
and is a precursor to integrating an organization with its partners
and suppliers. Consistency is an important factor for this configu-
ration as it provides both a uniform view to the enterprise and its
customers as well as ensuring compliance with statutory or business
policy requirements.
One problem when implementing an SOA at the enterprise level or imple-
menting a cross-enterprise collaborative SOA is how to manage the SOA
model, how to categorize the elements in this model, and how to organize
them in such a way that the different stakeholders reviewing the model can
understand it. Toward this end, it is often convenient to think of the SOA as
comprising a number of distinct layers of abstraction that emphasize service
interfaces, service realizations, and compositions of services into higher-
level business processes. Each of these describes a logical separation of con-
cerns by defining a set of common enterprise elements; each layer uses the
functionality of the layer below it, adding new functionality, to accomplish
its objective. The logical flow employed in the layered SOA development
model may focus on a top-down development approach, which emphasizes
how business processes are decomposed into a collection of business ser-
vices and how these services are implemented in terms of preexisting enter-
prise assets.
SOA can considered to be comprised of the following six distinct layers:
1. Domains : A business domain is a functional domain comprising a set
of current and future business processes that share common capa-
bilities and functionality and can collaborate with each other to
accomplish a higher-level business objective, such as loans, insur-
ance, banking, finance, manufacturing, marketing, and human
resources.
2. Business processes : This layer is formed by subdividing a business
domain, such as distribution, into a small number of core business
processes, such as purchasing, order management, and inventory,
which are made entirely standard for use throughout the enterprise;
having a large number of fine-grained processes leads to tremen-
dous overhead and inefficiency, and hence, having a small collection
of coarser-grained processes that are usable in multiple scenarios is
a better option.
3. Business services : For any process, the right business services is to
subdivide it into increasingly smaller subprocesses until the pro-
cess cannot be divided any further. The resulting subprocesses
then become candidate indivisible (singular) business services for
implementation. Business services automate generic business tasks
that provide value to an enterprise and are part of standard business