Position summary: supporting disconnected operation in DOORS

The increasing popularity of portable computers opens the possibility of collaboration among multiple distributed and disconnected users. In such environments, collaboration is often achieved through the concurrent modification of shared data. DOORS is a distributed object store to support asynchronous collaboration in distributed systems that may contain disconnected computers. In this summary we focus on the mechanisms to support disconnected operation. The DOORS architecture is composed by servers that replicate objects using an epidemic propagation model. Clients cache key objects to support disconnected operation. Users run applications to read and modify the shared data (independently from other users)-a read any/write any model of data access is used. Modifications are propagated from clients to servers and among servers as sequences of operations-the system is log-based. Objects are structured according to an object framework that decomposes object operation in several components. Each component manages a different aspect of object execution. Each object represents a data type (e.g. a structured document) and it is composed by a set of sub-objects. Each sub-object represents a subpart of the data type (e.g. sections). A new object is created composing the set of subobjects that store the type-specific data with the adequate implementations of the other components. The following main characteristics are the base to support disconnected operation in DOORS.