CS 490

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CS 490

• Design Patterns

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Introduce Yourself

• Your name
• What attracted you to this course?
• Experience with Design Patterns.
• How would you define Design Patterns at this
  point.
• Ill go first.

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Will this be a hard course?

• Why not? (sorry if thats a disappointment)
• New material for me.
• Exhaustion after two terms.
• Mine (and probably yours).
• Freedom to explore.
• Spring is coming!
• I will try to provide a framework in which you
  can productively learn a lot.
• I will not spend much time cracking the whip.

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My model

• Lewis and Clark
• A great book Undaunted Courage by Stephen
  Ambrose.
• None of us have been this way before.
• I organize the expedition.
• We are all scouts, exploring and reporting on
  what we have seen.
• Dont know exactly where we will go or what we
  will see.
• It worked well for AOP.
• If you dont like this approach, take a different
  trip!

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Things that influence your grade

• Project (which you propose and I approve).
• Class Participation (your presentations and
  otherwise).
• Focus group at end of term where I will ask you
  to sit down with others and discuss some course
  issues while I mainly listen.
• Perhaps a few specific homework assignments.
• Journal of your course activities.
• Day-by-day log of time spent and what you did.
• Reactions to things you have read.
• More details soon.

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The Blind Men and the Elephant

• by John Godfrey Saxe

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• It was six men of Indostan
• To learning much inclined,
• Who went to see the Elephant
• (Though all of them were blind),
• That each by observation
• Might satisfy his mind

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• The First approached the Elephant,
• And happening to fall
• Against his broad and sturdy side,
• At once began to bawl
• God bless me! but the Elephant
• Is very like a wall!

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• The Second, feeling of the tusk,
• Cried, Ho! what have we here
• So very round and smooth and sharp?
• To me tis mighty clear
• This wonder of an Elephant
• Is very like a spear!

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• The Third approached the animal,
• And happening to take
• The squirming trunk within his hands,
• Thus boldly up and spake
• I see, quoth he, the Elephant
• Is very like a snake!

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• The Fourth reached out an eager hand,
• And felt about the knee.
• What most this wondrous beast is like
• Is mighty plain, quoth he
• Tis clear enough the Elephant
• Is very like a tree!

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• The Fifth, who chanced to touch the ear,
• Said Een the blindest man
• Can tell what this resembles most
• Deny the fact who can
• This marvel of an Elephant
• Is very like a fan!

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• The Sixth no sooner had begun
• About the beast to grope,
• Than, seizing on the swinging tail
• That fell within his scope,
• I see, quoth he, the Elephant
• Is very like a rope!

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• And so these men of Indostan
• Disputed loud and long,
• Each in his own opinion
• Exceeding stiff and strong,
• Though each was partly in the right,
• And all were in the wrong!

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• So oft in theologic wars,
• The disputants, I ween,
• Rail on in utter ignorance
• Of what each other mean,
• And prate about an Elephant
• Not one of them has seen!

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• What do some who may be less blind than I say?
• Most of these quotes are from James Coopers Java
  Design Patterns, a Tutorial, available via Safari
  On-line.

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• "Design patterns are recurring solutions to
  design problems you see over and over."
  Smalltalk Companion
• "Design patterns constitute a set of rules
  describing how to accomplish certain tasks in the
  realm of software development." Pree, 1994

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• "Design patterns focus more on reuse of recurring
  architectural design themes, while frameworks
  focus on detailed design... and implementation."
  Coplien and Schmidt, 1995
• "A pattern addresses a recurring design problem
  that arises in specific design situations and
  presents a solution to it." Buschmann and
  Meunier, et al., 1996

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• "Patterns identify and specify abstractions that
  are above the level of single classes and
  instances, or of components." Gamma, Helm,
  Johnson, and Vlissides, 1993

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Textbook choice

• Most important and influential Patterns book?
• What do you think?
• Gang of Four book
• Why not use it as main textbook?
• Most influential math books?
• Most influential CS books?

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How to use the textbook

• Dont gloss over the Challenges.
• They are the most important part of the book.
• Dont look at answers too quickly.
• Do look at answers before you go on.
• My experience.
• Had more trouble with early challenges than with
  late ones.
• Read Foreword, Preface, and Chapters 1 and 2.

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Overview vs. example.
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Video

• Richard Helm
• Write down
• terms that need defining for you.
• reactions
• questions.