Goal models described with the Goal-oriented Requirement Language (GRL) are amenable to various kinds of analyses, including quantitative and qualitative propagations of satisfaction values. However, most approaches use bottom-up evaluations involving operational semantics that can only answer what if questions. This paper introduces a new declarative semantics for GRL based on a constraint-oriented interpretation of goal models. This semantics enables constraint solvers to evaluate and optimize goal models in a way that is more generic than bottom-up and top-down propagation techniques, hence enabling other questions to be answered. A prototype that combines the jUCMNav modeling tool and the JaCoP constraint solver to support quantitative evaluations is used to demonstrate the feasibility and potential of this new approach.