Extending Tuplespaces for Coordination in Interactive 课件.ppt

Simple and Portable client API Reduced number of API calls and amount of code Easy Debugging Easy to figure out and debug interactions Perceptual Instantaneity Coordinations and actions instantaneous to user Latencies minimized (i.e 50 ms for round trip) Failure Tolerance and Recovery Mechanisms for coping with failures Application Portability Coordination infrastructure independent from IW. Scalability to Workspace-sized Traffic loads Load limited by number of entities connected and rate of updates Interactive Workspace Desired Properties (cont.) Properties Supported by Coordination Infrastructures In RMI/RPC: Perceptual Instantaneity only In Tuplespace Model and Pub-Sub: Referential Decoupling Simple and Portable Client API Perceptual Instantaneity Extensibility (limited support) Easy debugging (limited support) In Pub-Sub and MOM: Application portability Query persistence and notification via subscription In Tuplespace Model also: Limited Temporal Decoupling Expressiveness Failure Tolerance and Recovery (limited support) Further Reading: InfoBus system Eugster et al. overview Siena system Tuplespace Model has most properties needed for Interactive Workspaces. Linda Tuplespace Model*for parallel computing Goal: add concurrent programming capability to sequential programming Need strong decoupling of processes in space, time and reference Solution: place data as tuples in the space for process coordination Tuple: object named by tag and key (similar to content addressable memory) symbolic name + an ordered list of typed values equally accessible to all processes but bound to none Tuplespace: “shared memory for accessing, modifying and deleting tuples data fields in space matched with elements in requesting template must have same number of fields, same types of fields in same order, (possibly identical values as in the template) retrieval made blocking when there is no match actuals assigned to formals when match found. *Carriero and Gelernt