Modeling of Dynamic Behavaior and Sequence Diagrams

1. UML Sequence Diagrams
   illustrate the dynamic behvaior of a system
   show the actors and objects which comprise the system and the messages sent between them
   have actors and objects represented by rectangles, drawn left-to-right across the top of the diagram
   show a timeline for the actor/object below each of the actor/objects
   use a narrow vertical rectangle to indicate the lifetime of the object;
   use a dotted line to indicate the part of the timeline when the object does not exist
   draw arrows between the timeline rectangles, to indicate messages (method calls and replies) sent between objects

   

2. Some Design Guidelines
   Get the Big Picture

   • Understand the problem
   • Think objects

   Encapsulation

   • Maximize encapsulation
   • Minimize coupling
   • Separate the GUI

   Designing Classes

   • A Class Needs a Purpose
   • Classes vs. Attributes
   • Composition vs. Inheritance
   • Don't Make Classes Too Big

   Inheritance

   • Use the Is-A Test
   • Move Attributes and Operations as High as Possible (But Not Too High)
   • Look for Superclasses

   General Guidelines

   • Choose appropriate names
   • Don't reinvent the wheel
   • Refine the design
   • Keep it simple
   • Plan for the future