Single Responsibility Principle

• Classes should have one and only one job
• If this principle is broken, it becomes increasingly difficult to:
  • Track a bug or feature
  • Minimize the impact of requirement changes
  • Write automated unit tests
• A class should only have one reason to change

Liskov Substitution Principle

• The idea behind Liskov substitution is that a parent class can be replaced by a subclass without breaking the application
• Minimizes coupling and maximizes reuse

Interface Segregation Principle

• The more poorly implemented methods, the more likely that domain boundaries are not set correctly in your design.
• Major coding patterns will not function appropriately if interfaces are not implemented correctly
• If you consider what external users will see when trying to use your class it makes a lot of sense - if there are 200 methods, and 198 of them have empty implementations, there's a design problem
• General printer interface should be replaced with Print, Scan, Fax

Dependency Inversion Principle: Why?

• A Patient monitor class is tightly coupled with specific alert mechanisms
• Implement the dependency inversion principle by introducing an alert interface, serving as an abstraction to decouple patient monitor from specific alert mechanisms, enhancing flexibility.

Sequence Diagram

• Sequence models show the sequence of object interactions that take place
• Usually considers small, discrete pieces of the system, eg.., individual use cases or operations
• Horizontal Axis is for objects: objects that initiate interaction are the leftmost
• Vertical Axis is for time

Message Passing

• Call : Invoke an operation, shown with a filled arrowhead
• Send : Sends a message to an object, shown with an open arrowhead
• Return : Returns a value to called, shown with a dashed line
• Create : Creates an object, shown with a dashed line with an open arrowhead

Interaction Fragments

• Interaction use L an interaction fragment which allows to call another interactions

Type	Full Name
alt	alternative
opt	option
loop	iteration
break	break
par	parallel
strict	strict sequencing
seq	weak sequencing
critical	critical region
ignore	ignore
consider	consider
neg	negative

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