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Transitional Page. Title: PATTERNS DESIGN. Design by: Zahid Iqbal . Definition:.
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Transitional Page
Title: PATTERNS DESIGN Design by: Zahid Iqbal
Definition: • “ 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.”
Definition2: • “Description of communicating objects and classes that are customized to solve a general design in a particular context [GOF].”
Historical perspective: • 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.
Software patterns: • STL (c++ template library) • Algorithms and data structure . • Object oriented analysis patterns [peter Coad] • Software idioms [coplien] • Antipatterns [brown]
Frameworks: • -Framework is a set of cooperative classes that makes up reusable design of a system. • -Framework dictates the architecture of the software.
Design patterns: • 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 phrase • Problem • - A statement of the problem which describes its intent ; the goals of objectives it wants to reach with in the given context and forces.
Motivation: • Context • -preconditions under which the problem and its solution seem to occur • - the patterns applicability • - May change over time.
solution • 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
Example: • 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
Rationale • 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
Related patterns • The static and dynamic relationships between this patterns and other patterns known uses • To demonstrate that this is proven solution to a recurring problem.