# 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.