Web services interface policy constraints may be specified in a policy constraints language and policy processing, such as generating an intersection policy of two policies may be automated by a policy-processing engine. A policy constraint may be a specification of a value, range of values, or set of values that a particular requirement or offering is allowed to have. Hierarchies of requirements and/or offerings may also be expressed and matched such that a more specific case of a requirement or offering may be matched against a more general case of the same requirement or offering. Also, preferences among vocabulary items, vocabulary item values, policy constraints, and other elements of a policy may be specified and automatically determined by a policy-processing engine. Automated matching of consumer requirements against provider offerings may allow a policy-processing engine to process policies with specifications of requirements or offerings from any domain-specific schema.