Information about user preferences plays a key role in automated decision making.As a intuitive graphical tool for representing statements over multiple attribute qualitative decision

CP-nets has attracted many researchers to study it.Its higher complexity of dominance query algorithm is a difficult problem to solve.We study how to reduce dominance query complexity.A general-purpose framework for solving constraint satisfaction problem is introduced

namely

SCSP (c-Semiring Constraint Satisfaction Problem)

and point out that conditional preference table of CP-nets just is a type of dynamic constraint.An algorithm transforming conditional preference table of CP-nets to constraint of SCSP is given

which can judge a solution is better or worse.Its polynomial time complexity property is given

so based on c-Semiring

dominance query for acyclic CP-nets is solved effectively.