We present SOS, the operating system for SOMIW (Secure Open Multimedia Integrated Workstation). The SOS is object-structured; all services and communication is expressed in terms of passive objects with procedural interfaces.Resources are accessed by clients via a local (to the client) proxy object. The possibly distributed or group nature of the resource is hidden behind the proxy interface.The service and its representatives form a single distributed object (or group); any communication protocol is hidden, as part of its internal representation. The proxy is a programmable capability and may be different per-client. This approach also allows the programmer of a resource to cope with the heterogeneous nature of its clients.The OS is based on a kernel which implements contexts, processes, memory segments and object descriptors. Object invocation normally occurs within one context, but may trap transparently into an other context.