| Interface | Description | 
|---|---|
| Window<M,K,WV> | Groups incoming messages in the  MessageStreaminto finite windows for processing. | 
| Class | Description | 
|---|---|
| WindowKey<K> | Key for a  WindowPaneemitted from aWindow. | 
| WindowPane<K,V> | Specifies the result emitted from a  Window. | 
| Windows | APIs for creating different types of  Windows. | 
| Enum | Description | 
|---|---|
| AccumulationMode | Specifies how a  Windowshould process its previously emittedWindowPanes. |