Expressing advanced user preferences in component installation

State of the art component-based software collections—such as FOSS distributions—are made of up to dozens of thou-sands components, with complex inter-dependencies and con-flicts. Given a particular installation of such a system, each request to alter the set of installed components has poten-tially (too) many satisfying answers. We present an architecture that allows to express ad-vanced user preferences about package selection in FOSS distributions. The architecture is composed by a distribution-independent format for describing available and installed packages called CUDF (Common Upgradeability Descrip-tion Format), and a foundational language called MooML to specify optimization criteria. We present the syntax and semantics of CUDF and MooML, and discuss the partial evaluation mechanism of MooML which allows to gain effi-ciency in package dependency solvers