Conventional approaches to access-control, such as ACLs, do not scale well enough for distributed systems. Capabilities on the other hand offer scalability and adaptability advantages in large-scale distributed environments due to their being held and managed by the system's users/agents rather than by the middleware. However the structure of capabilities is only able to provide simple sequence-independent rights-based control, which precludes most forms of composition of actions. If required,

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... uch fine-structure behavioural control would be the responsibility of the middleware, thus negating some of a capability system's advantage. Therefore we propose the concept of Treaties: a generalization of capabilities whereby sequence of actions can be specified, and enforced. Treaties can be safely modified and combined by, and passed between, system agents with minimal middleware involvement, enabling rich and complex ensembles of cooperating agents to be formed. This paper outlines the motivation and structure of treaties and their operations, covering the design space focusing on the new implementation issues raised, and ending with preliminary implementation results.