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About patterns

About patterns. Outline What’s a pattern? An example from fast food Comments on the “definition” Patterns and software development culture Pattern definition exercises. What’s a pattern?. Alexander’s characterization (quoted by Fowler) Recurring problem Environment in which it occurs

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About patterns

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  1. About patterns Outline • What’s a pattern? • An example from fast food • Comments on the “definition” • Patterns and software development culture • Pattern definition exercises Pattern-Oriented Cluster: Comp 630/650/655

  2. What’s a pattern? Alexander’s characterization (quoted by Fowler) • Recurring problem • Environment in which it occurs • Core of a solution • Has been used successfully multiple times • Can be used many times without ever doing it the same way twice Pattern-Oriented Cluster: Comp 630/650/655

  3. Example: fast food pattern • Problem: people getting burned on hot drinks • Environment: fast food restaurants • Solution: print warnings on packaging • Name: Achtung - Heiss Pattern-Oriented Cluster: Comp 630/650/655

  4. Other solutions • Solution: make in advance, heat to safe temperature when serving • Name: Heat-n-Serve • Solution: make drinks at safe temperatures • Name: Low-Temperature Recipe Pattern-Oriented Cluster: Comp 630/650/655

  5. What’s the real problem? • Heat-n-Serve and Low-Temperature Recipe are about preventing burns • Achtung-Heiss is about preventing lawsuits Pattern-Oriented Cluster: Comp 630/650/655

  6. Definition vs Characterization Definition: Duck • Any of numerous relatively small and short-necked web-footed swimming birds of the family Anatidae. Characterization: Duck • Walk: waddle • Sound: quack Patterns characterize more than they define Pattern-Oriented Cluster: Comp 630/650/655

  7. Comments on the characterization • Patterns have consequences • Some patterns go together Class Table Inheritance (285) usually implies Domain Model (116) • Using a pattern can introduce other problems Developers often have trouble getting comfortable with Domain Model (116) • Architecture patterns differ from GOF • It’s all Indirection … Pattern-Oriented Cluster: Comp 630/650/655

  8. Patterns and software culture • At best: gray heads use patterns to help younger people without being dogmatic • At worst: pattern writers kill lots of trees • At best: patterns make communication more efficient • Huffman codes for architecture/design descriptions • Can save effort in project design documentation • At worst: patterns add confusion • People may have different understandings of a pattern Pattern-Oriented Cluster: Comp 630/650/655

  9. More on patterns and culture • Naming patterns is • Really important • Really hard • Patterns are owned by the community • Nobody invents patterns • You can’t patent a pattern • Patterns are “identified” or “discovered” • Pattern writers depend on feedback • Especially about naming, applicability, consequences Pattern-Oriented Cluster: Comp 630/650/655

  10. One more comment … • The analogy between building architecture and software architecture • Can be helpful • Can be over-used Pattern-Oriented Cluster: Comp 630/650/655

  11. Pattern definition exercises • Environment given, or picked as first step • Brainstorm recurring problems in the environment • Pick a recurring problem to work on • Identify the core of a solution • Not (on purpose) a Fowler pattern • Pick a name • Present to the class Pattern-Oriented Cluster: Comp 630/650/655

  12. Pattern exercise 1 • Environment: group project • Note: this is not necessarily a software project Pattern-Oriented Cluster: Comp 630/650/655

  13. Pattern exercise 2 • This one is about software • Environments to choose from: • Database • Web presentation • Performance/capacity • Source code control/configuration management • Or, brainstorm some other environment Pattern-Oriented Cluster: Comp 630/650/655

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