How is information hiding different from information shyness

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How is information hiding different from
information shyness

• CACM May 1972 A technique for the specification
  of software modules Hide implementation data
  structures.
• Later CACM Dec. 1972 Secret design decision
  which a module hides from all the others.
• Shyness hide a concern (e.g., structure)

2
Protect Against Changes.

• Protection against changes in data representation
  and interfaces. Traditional technique
  information-hiding is good to protect against
  changes in data representation. Does not help
  with changes to interfaces.
• Need more than information hiding to protect
  against interface changes restriction through
  shy programming, called Adaptive Programming (AP).

Implementation
Interface
Client
Shy Programming
Representation Independence
Information Hiding
3
Strengthening Information Hiding?
may change in limits
may change
Implementation
Interface
Client
Shy Programming
Representation Independence
Information Hiding
4
Problem with Information Hiding

• Shy Programming builds on the observation that
  traditional black-box composition is not
  restricting enough. We use the slogan
  information hiding is not hiding enough. Blackbox
  composition isolates the implementation from the
  interface, but does not decouple the interface
  from its clients.

5
Cover unimportant parts of the interface

• To permit interfaces to evolve, self-discipline
  is required to prevent from programming
  extensively against the interface. Certain parts
  of the interface are best left as if they were
  covered.

Implementation
Interface
Client
Representation Independence
Shy Programming
Information Hiding
6
Shy Programming Adaptive Programming

• This disciplined programming is referred to as
  shy programming. Shy programming lets the
  program recover from (or adapt to) interface
  changes. Shy programming is also called Adaptive
  Programming (AP). This is similar to the shyness
  metaphor in the Law of Demeter (LoD) structure
  evolves over time, thus communicate with just a
  subset of the visible objects.

7
Decoupling of Interface

• We summarize the commonalities and differences
  between black-box composition and Shy Programming
  into two principles.
• Representation-Independence Principle the
  representation of objects can be changed without
  affecting clients.
• Shy-Programming Principle the interface of
  objects can be changed within certain limits
  without affecting clients.
• It is important to notice that the
  Shy-Programming Principle builds on top of the
  Black-Box principle.

8
Layers

• The interface of one layer becomes representation
  for the next layer.

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are the program (a,b) is the abstraction
axb