05-12-2012, 02:05 PM
Time and Space
Time and Space.pptx (Size: 490.75 KB / Downloads: 27)
Frictionless environment
Messages are sent in zero time
Network never go down
Workstations never fail
And so on
But the real world doesn’t work that way
Have to take into account the issues of time and space
To represent the modeling needs of real-time and distributed systems, the UML provides a graphic representation for timing marks, time expressions, timing constraints, and location
Timing mark:
A denotation for the time at which an event occurs
Graphically, it is formed as an expression from the name given to the message
Time expression:
is an expression that evaluates to an absolute or relative value of time
Modeling objects that migrate
Certain classes of distributed systems will move
Two reasons:
In order to move closer to actors and other objects they need to work with to do their job better
In response to the failure of a node or connection or to balance the load across multiple nodes.