1. A method comprising: generating, by a computer system, a runtime policy set for a web service endpoint, the runtime policy set identifying a list of all web service policies that can be attached to the web service endpoint and, for each web service policy, a corresponding constraint expression; aggregating, by the computer system, the web service policies included in the runtime policy set into a set of groups, the aggregating being performed by constraint expression; identifying, by the computer system, one or more groups in the set of groups that will be simultaneously attached to the web service endpoint at runtime; and applying, by the computer system, one or more validation rules to the web service policies in the one or more groups.