# Package cascading.scheme

- Interface Summary
  Interface | Description
  --- | ---
  SinkCall<Context,Output> | SinkCall provides access to the current `Scheme.sink(cascading.flow.FlowProcess, SinkCall)` invocation arguments.
  SourceCall<Context,Input> | SourceCall provides access to the current `Scheme.source(cascading.flow.FlowProcess, SourceCall)` invocation arguments.

- Class Summary
  Class | Description
  --- | ---
  ConcreteCall<Context,IO> | The concrete base class for `SourceCall` and `SinkCall`.
  NullScheme<Config,Input,Output,SourceContext,SinkContext> | Class NullScheme is a `Scheme` that neither reads or writes any values.
  Scheme<Config,Input,Output,SourceContext,SinkContext> | A Scheme defines what is stored in a `Tap` instance by declaring the `Tuple` field names, and alternately parsing or rendering the incoming or outgoing `Tuple` stream, respectively.

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