Informatics 122 Software Design II

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Informatics 122Software Design II

• Lecture 6Emily Navarro
• Duplication of course material for any commercial
  purpose without the explicit written permission
  of the professor is prohibited.

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Todays Lecture

• Design aesthetics
• Your BeNumbered designs

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But first A Few Updates about Assignment 2

• Deadline extended to Tuesday, February 4
• Remember, no real GUI is required
• But you should show the intermediate boards
• after each sequence is removed but before the
  spaces are filled in with random numbers
• and after the spaces are filled in with random
  numbers

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Design Aesthetics

• What makes a given software implementation design
  beautiful?
• What is it that makes someone appreciate a
  particular software implementation design?
• What are the qualities that determine whether a
  particular software implementation design is
  good or bad?
• What is it, then, that we can strive for in
  creating a software implementation design that
  will help others in appreciating it?

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Purpose of Implementation Design

• An implementation design is a road map
• An implementation design describes a path from
  application / interaction / architecture design
  to the product
• An implementation design describes what the
  implementers should do
• An implementation design is a guide towards
  future change

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Purpose of Implementation Design

• An implementation design is a road map
• understandable, unambiguous, consistent, helpful,
  
• uses a good naming schema
• An implementation design describes a path from
  application / interaction / architecture design
  to the product
• correct, complete, concise, verifiable,
  effective,
• attention to detail, well-documented, has clear
  flow, has a clear layout, has a clear interaction
  between classes, uses UML syntax correctly
• An implementation design describes what the
  implementers should do
• elegant, partitionable, recomposable, resilient,
  
• An implementation design is a guide towards
  future change
• evolvable,

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Less of a Shared Understanding

• An implementation design is a road map
• understandable, unambiguous, consistent, helpful,
  
• uses a good naming schema
• An implementation design describes a path from
  application / interaction / architecture design
  to the product
• correct, complete, concise, verifiable,
  effective,
• attention to detail, well-documented, has clear
  flow, has a clear layout, has a clear interaction
  between classes, uses UML syntax correctly
• An implementation design describes what the
  implementers should do
• elegant, partitionable, recomposable, resilient,
  
• An implementation design is a guide towards
  future change
• evolvable,

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Some Caveats

• We are going to be showing, praising, and
  critiquing your designs
• not to ridicule, rather to provide constructive
  feedback
• This is a normal part of any design studio class
• Rules of the game
• do not identify someone, even if you know whose
  design it is
• someone may choose to volunteer and explain their
  design, but they may also choose not to do so
• We only highlight parts of certain designs, so
  please do not correlate our comments here with
  your final grade for this assignment

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Designs Rated Highly By Peers

• 20
• 10
• 1
• 25
• 21

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Some Obvious Room for Improvement

• 15
• 11
• 6
• 19
• 7

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Important Points to Observe (Assignment)

• Being a 1 or a 5 on someones ranking is not
  an absolute evaluation
• if you are a 1 on someones ranking, the other
  designs may have all been relatively poor
• if you are a 5 on someones ranking, the other
  designs may have all been relatively stellar
• Length of the document may be an indicator in
  peers rankings, but not necessarily in ours
• It is easier to review than to design, or is it?

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Important Points to Observe (UML)

• Having a document heavy on UML by itself is not
  a guarantee for a great design
• it may indeed be more complete
• it may also be less understandable
• If we cannot find the flow in the UML diagram,
  something tends to be wrong
• for some designs, we end up searching for their
  meaning
• for others, it is clear from the diagram
• physical layout, often, has something to do with
  this
• Design languages are a factor
• UML by itself is insufficient

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Important Points to Observe (Process)

• Where to start?
• what about with the set of nouns in the
  description of the problem (e.g., grid, cell,
  sequence, flame number, )
• what about with the set of verbs in the
  description of the problem (e.g., chooses
  adjacent cells, cells are swapped, cells are
  emptied )
• Work towards completeness
• does my current design account for all possible
  features
• does it do so explicitly, or are some features
  hidden
• This is merely a rough and rules of thumb
  process, but one that tends to help the beginning
  designer

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A Checklist for the Overall Process

• Apply rigor
• Separate concerns
• modularize
• abstract
• Anticipate change
• Generalize
• Work incrementally

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A Checklist for Overall Design

• Strive for grouping related functionality (high
  cohesion)
• Strive for ungrouping semi-related functionality
  (high cohesion)
• Strive for reducing interdependency (low coupling)

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A Checklist on Class Design

• Cohesion
• Completeness
• Convenience
• Clarity
• Consistency

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A Checklist on Principles and Strategies

• Principles
• keep it simple, stupid! (KISS)
• information hiding
• acyclic dependencies
• Strategies
• program to the interface
• refactor
• apply software patterns