Chapter 1 What Is Architecture?
What does it mean to create architecture? It means that you have
created a software infrastructure that addresses the service-level
requirements that have been identified for the system. For example, if
the system has a service-level requirement that states no user response
time will be greater than three seconds, the software infrastructure you
create must ensure that the system can meet this requirement. It also
means that you have given the designers an infrastructure that allows
them to design and code the system without worrying about compromis-
ing this service-level requirement. One of the real issues around archi-
tecture is: When does the creation of an architecture stop and the design
process begin? There is not a definitive answer for every system. This
issue of architecture and design can be summed up in terms of focus and
control. Architecture defines what is going to be built, and design out-
lines how you will build it. One or a few individuals who focus on the big
picture control the architectural process, and design is controlled by
many individuals who focus on the details of how to achieve the big pic-
ture. An architect creates architecture to a point where the design team
can use it to make the system achieve its overall goals. So, if you are cre-
ating an architecture for experienced designers, you would not produce
as much detailed documentation that you would need if you had a group
of less-experienced designers.
As you create an architecture to satisfy the business and service-level
requirements of a system, you usually don’t have unlimited funds to pur-
chase hardware, software and development resources, so you need to
make the system work within your predefined limitations. For example,
how can you make the system scale to meet the demands of the Internet
age, when you have only a single computer to support your internal
employees? How do you create architecture without funds to buy soft-
ware products? These are examples of problems faced by architects
when they are creating system architecture. You will be presented with
many difficult choices and make many trade-offs to solve these types of
problems when creating your architecture. As you make these trade-
offs, it is important that you document each decision made regarding the
architecture of the system, so developers understand why decisions were
made, and you should not receive questions from developers about
those trade-offs. If you make a decision to have an Oracle database
persist the objects in the system, you should document why you chose
Oracle over another database vendor. This allows others working on the
project or entering the project at a later time to understand why deci-
sions were made and prevents you from justifying your decision over and
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