Abstraction

• The book Abstraction: A mental model that removes complex details.
  • I might remove mental.
  • I don't think I like "complex" either.
• The book points out Miller's Law:
  • The average person can keep about seven "objects" in working memory at one time.
  • The Magic Number Seven, Plus or Minus Two.
• The implication is that we can not deal with all of the facts of a given item at one time.
  • So we are exceptionally good at abstraction.
  • We only pay attention to the important details and group everything else together.
• When you are playing a game on your phone
  • Are you concerned about anything about the phone but the items you use for interaction.
  • And even then, are you concerned about how a touch screen works, or just where to touch on the screen.
• Pop up an on screen calculator
  • Do those buttons really exist?
  • You are using an abstraction.
  • There are many details about where on the screen the button was pressed, which button was pressed, what programs were active at the time, ...
• Think about cities in games
  • In some high level strategic games, a city might be just a supply point. You might have few or no details other than it exists.
  • (Board Game Geek, Axis and Allies)
  • In a tactical game, a city could be roads and buildings.
  • (Board Game Geek, Advanced Squad Leader)
  • In a simulation, like simcity, it is a large number of details such as roads, buildings, infrastructure, ...
    • 
    • But even here, we use abstractions.
    • We build a School, we don't worry about the bricks, tiles, teachers or students, we just have a building.
• A major skill in life is dealing with abstractions.
  • We focus on the details that are important and remove those that are not.
  • When you drive, do you worry about
    • How the engine works?
    • How the roads are constructed?
    • All of the traffic laws?
    • All of the laws of physics?
    • All of the other cars on the road?
• A major skill in computer science is producing the correct abstraction.
• Closely related to abstraction is information hiding.
  • Information Hiding: A technique for isolating programs pieces by eliminating the ability for one piece to access information in another.
  • Semi Example: a seal on the back of a keyboard or device.
    • You don't need to know how the keyboard works.
    • So they are "hiding" the implementation from you by making it difficult to get to.
  • Information hiding enforces abstraction.