Resumen
The article focuses on two remaining areas of distributed systems development, timely interaction and access control. The latter includes enabling nonexpert administrators to use tools to express and modify access-control policies, so such policies can be automatically checked for consistency and enforced. It outlines work on event-based middleware, then describes Open Architecture for Secure, Interworking Services (OASIS) along with related work on access-control policy expression and enforcement. Many authors have argued that role-based access control (RBAC) is a realistic way to provide scalable policy expression for access control in large-scale systems, yet most work on RBAC has used a single organizationwide role-management model and privilege delegation. The article, begins with the assumption of widely distributed systems with many independently managed domains needing to interoperate. The result is OASIS, which includes an architecture and a formal model, engineering in the context of several practical applications is under way.