Registering Operators and Building Logical Paths

• Operator Registry

  • Based on Service Discovery Service (SDS)
  • Operators required to ìcheck inî with registry periodically; operators which fail to do so in a specified time period are removed from registry.
  • Registry base-class implements all polling and initialization of services.

• Path Creation

  • Users provide RMI stubs to two end-points, located via SDS or some other Ninja location method, and also specify specific intermediate operators.
  • Yields a ìlogical pathî: named operators without specific machines.
  • Automatic Path Creator (APC) completes the path by inserting operators into the path until all input and output data-types in operator XMLs match.

    • Match(Op A, Op B) _ Output XML of A _ Input XML of B (XSet)
    • Allows operators with wildcard inputs, but not outputs.
    • Not semantic: system does not ìunderstandî datatypes
    • Algorithm: Maintain graph of operators via SDS, directional edges represent operator compatibility. To build a path from Op A to Op B, use BFS to find shortest path A to B.

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