In the general framework of a constraint-based grammar formalism often some sort of feature logic serves as the constraint language to describe linguistic objects. We investigate the extension of basic feature logic with subsumption (or matching) constraints, based on a weak notion of subsumption. This mechanism of oneway information flow is generally deemed to be necessary to give linguistically satisfactory descriptions of coordination phenomena in such formalisms. We show that the problem whether a set of constraints is satisfiable in this logic is decidable in polynomial time and give a solution algorithm. be informally described as a device,.