Amir Yousefi

An overview on

Definition : Fowler

In most successful software projects, the expert

developers working on that project have a

shared understanding of the system design. This

shared understanding is called ‘architecture.’

This understanding includes how the system is

divided into components and how the

components interact through interfaces. These

components are usually composed of smaller

components, but the architecture only includes

the components and interfaces that are

understood by all the developers…Architecture is

about the important stuff. Whatever that is.

Definition : Booch

All architecture is design but not all design is

architecture. Architecture represents the

significant design decisions that shape a system,

where significant is measured by cost of change.

Kirk:

the goal of software architecture must be

to eliminate the impact and cost of change

Kirk:

The best way to deal with architecture is to

eliminate it.

The paradox

the way to eliminate architecture by minimizing

the impact of cost and change is through

flexibility

The more flexible the system, the more likely

that the system can adapt and evolve as

necessary

But…

The paradox

The paradox

making everything easy to change makes

the entire system very complex

Lehman's 2nd law

As a system evolves its complexity increases

unless work is done to maintain or reduce it

Gall's law

A complex system designed from scratch never

works and cannot be made to work. You have to

start over, beginning with a working simple

system

Defeating Complexity

Defeating Complexity

Defeating Complexity

Modularity

It is all the way down

Reuse Release equivalence

?

Reducing complexity

Joints

Joints

Shared understanding

Shared understanding