Question

1. Describe a task that can be solved using constraints.
   1. Distinguish between the hard constraints and the soft constraints of the system.
   2. Develop a model of the constraint based solution using a table or a diagram.

Answer 1

a.)

Hard constraints	Soft constraints
Absolutely non-negotiable	Negotiable if necessary
Always respected by the scheduler	Usually respected by the scheduler
Exceptions are never made	Exceptions are made if it's the difference between generating a schedule and not generating one
Usually make the scheduler run slower	No impact on scheduler speed
Decrease likelihood that the scheduler will find any schedules	Likelihood of finding schedules not affected
Too many hard constraints may mean not getting any schedules	No penalty for having lots and lots of soft constraints

b.) Task that can be solved using constraints :- consider the Sudoku problem again. Suppose that a row, column and block already have 3, 5 and 7 filled in. Then the domain for all the variables in that row, column and block will be {1, 2, 4, 6, 8, 9}.

Flow chart of Constraint based programming  solving process.