1. Object-Oriented Analysis and Design

2. References
Grady Booch: Object-Oriented Analysis and Design with Applications; Addison Wesley
Perdita Stevens, Rob Pooley: Using UML Software Engineering with Objects and Components, Pearson
C. Larman : Applying UML and Patterns, Pearson
J. Rumbaugh, M. Blaha, W. Premerlani, F. Eddy, W. Lorensen: Object-Oriented Modeling and Design, PHI

3. Complexity Why software is inherently complex?
Complexity of problem domain
Difficulty of managing the development process
Flexibility possible through software
Problems of Characterizing the behavior of Discrete systems

4. Consequences
“The more complex the system, the more open it is to total breakdown”
adding a new sub-basement to an existing 100 storey building - builder VS. software system user – simple matter of programming
software crisis
time delay – over budget
deficient specification than requirement
squandering of human resource & loss of opportunities

5. Complete Dismal?
successful systems for significant complexity software
Space shuttle
large business organization (eg. Microsoft)
Study, understand, comprehend the complexity first

6. Complex System Attribute
1. Frequently, complexity takes the form of hierarchy, whereby a complex system is composed of interrelated subsystems that have in turn their own subsystems, and so on, until some lowest level of elementary components is reached.

7. Complex System Attribute
2. The choice of what components in a system are primitive is rarely arbitrary and is largely up to the discretion of the observer of the system.

8. Complex System Attribute
3. Intracomponent linkages are generally stronger than intercomponent linkages. This fact has the effect of seperating the high-frequency dynamics of the components – involving the internal structure of the components – from the low frequency dynamics – involving interaction among components.

9. Complex System Attribute
4. Hierarchic systems are usually composed of only a few different kinds of subsystems in various combinations and arrangements.

10. Complex System Attribute
5. A complex systems that works is invariably found to have evolved from a simple system that worked …. A complex system designed from a scratch never works and cannot be patched up to make it work.
Thus, one has to start over, beginning with a working simple system.

11. Organized-Disorganized Complexity
Canonical form of a complex system
little orientation - old pilot – new engine aircraft
similar skills –already – new to be trained
hierarchy not single - rather generalized one
“is a” hierarchy - class concept
“part of” hierarchy - object concept
collectively aka architecture

12. Organized-Disorganized Complexity
Limitation of the human capacity for dealing with complexity
intricacy of interaction
capability to think about many things at once ?
flight case – location, elevation, speed, heading
human comprehension is only at order of seven information
human mind takes 5 sec to accept new information

13. Decomposition algorithmic decomposition object oriented decomposition
straight, top-down structured
structure chart
directly from DFD & follows structured design
object oriented decomposition
depiction of key abstractions of problem domain
set of automated agents – collaboration for higher level behaviors
through message direction for a action

14. Role of Decomposition object oriented decomposition
yields smaller systems through the reuse of common mechanism
provides economy of expression
more resilient to change and thus better able to evolve over time – design based upon stable intermediate forms
evolve incrementally from smaller systems having already acquired confidence
separation of concerns in a large state-space

15. Role of Abstraction
“The span of absolute judgment and the span of immediate memory impose severe limitations on the amount of information that we are able to receive, process and remember. By organizing the stimulus input simultaneously into several dimensions and successively into a sequence of chunk we manage to break … this informational bottleneck” ---
Unable to master the entirety of a complex object - ignore its essential details, dealing instead with the generalized, idealized model of the object
semantic content

16. Role of Hierarchy depiction of different object collaboration
pattern of interaction – mechanisms
highlight common structure and behavior
semantic content exposition

17. Engg : as a science - an art
“The conception of a design for a new structure can evolve as much a leap of the imagination and as much a synthesis experience and knowledge as any artist is required to bring to his canvas or paper. And once that design is articulated by the engineer as artist, it must be analyzed by the engineer as scientist in as rigorous an application of the scientific method as any scientist must make”
- Petroski – To Engineer is Human

18. Design Meaning
satisfies a given (perhaps informal) functional specification
conforms to limitations of the target medium
meets implicit or explicit requirements on performance and resource usage
satisfies implicit or explicit design criteria on the form of artifact
satisfies restrictions on the design process itself, such as length or cost or the tools available for doing the design

19. Model Building Importance
Follows the principle of decomposition, abstraction and hierarchy
Each model within a design describes a specific aspect of the system under consideration
Seek to build new models upon old models (which gained confidence already)
Opportunity to evaluate each model under both expected and unusual situations

20. Design Method Elements
Notation – Language for expressing each model
Process – The activities leading to the ordinarily construction of the system’s model
Tools – The artifacts that eliminate the tedium of model building and enforce rules about the models themselves, so that errors and inconsistencies can be exposed
A sound design method is based upon a solid theoretical foundation, yet offers degrees of freedom for artistic innovation.

21. OO Model Logical Physical Dynamic Model Class & Object Structure
Module & Process Architecture
Static Model