In a computer system having a plurality of software components, a security system for controlling interactions between the software components, the security system including at least one constraint associated with the interaction; and at least one attribute associated with the software components. The attributes and interaction parameters are bound to the constraint. The security system reaches a verdict permitting or forbidding the interaction, by resolving the constraint, based on value of the attribute and values of the parameters. The security system uses constraints and attributes specified during different life stages of each software component, where constraints are incrementally added during each subsequent life stage.