Basic Operations of a Solver

• In order to be useful, solvers must implement some basic operations:

  1.

  Consistency (or satisfiability): check whether a constraint is consistent with those already accumulated

  2.

  Implication: check whether a constraint is entailed by another constraint in the store

  3.

  Projection of a constraint onto a set of variables

  4.

  Detection of uniqueness of variable value

• Actually, only the first one is really needed
• What are they for?

  1.

  Backtrack or continue with current path

  2.

  Decide whether a constraint must be deleted / added

  3.

  Give readable answers

  4.

  Transform non-determinate variable values into determinate ones $\rightarrow$ narrow the search