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Title:PATTERNS DESIGN Design by:

Zahid Iqbal

“ Each pattern describes a problem which occurs over and over again in our averment, and then describes the core of the solution to that problem in such a way that you can use this solution a million times over without ever doing it the same way twice.”

Definition:

“Description of communicating objects and classes that are customized to solve a general design in a particular context [GOF].”

Definition2:

1979 - Alexander's timeless way of building 1987 - OOPSLA workshop by beck and ward 1995 - GOF ( Gamma, helm, Johnson, vlissides) - Design patterns ; Elements of reusable object- oriented software.

Historical perspective:

- STL (c++ template library)- Algorithms and data structure .- Object oriented analysis patterns [peter Coad]- Software idioms [coplien]- Antipatterns [brown]

Software patterns:

-Framework is a set of cooperative classes that makes up reusable design of a system.-Framework dictates the architecture of the software.

Frameworks:

Design patterns follow a certain structure (some or all).- Pattern name (and category)- Intent- Motivation- Applicability- Structure- Participants- Consequences

Design patterns:

- Implementation- Known uses- Related patterns

Design patterns:

Name - Meaningful phraseProblem - A statement of the problem which describes its intent ; the goals of objectives it wants to reach with in the given context and forces.

Design patterns:

Context -preconditions under which the problem and its solution seem to occur - the patterns applicability - May change over time.

Motivation:

- Static and dynamic relationship describing how to realize the pattern

- Instruction how to construct the work products - Picture diagram prose which highlight the pattern

structure participants and collaboration

solution

- One or more samples application to illustrate.• A specific context• How the pattern is applied Resulting context - the state or configuration after the pattern has been applied.- Consequences (good or bad) of the pattern

Example:

- Justification of the steps or rules in the patterns - How and why it resolves the forces to achieves the

desired goals principles and philosophies - How are he forces orchestrated to achieve

harmony- How does the pattern work

Rationale

- The static and dynamic relationships between this

patterns and other patterns known uses- To demonstrate that this is proven solution to a

recurring problem.

Related patterns

Thanks???