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• Users must upgrade to new version if they want to use this functionality.

Rejected Alternatives

TBD

Rational for edits to the KIP

Due to changes to the project since KIP #150 was written there are a few items that may need to be updated.

First item that changed is the adoption of Materialized parameter.

The second item is the WindowedBy. How the KIP currently handles windowing is that it overloads the aggregate function to taking a Window object and an initializer. Currently the practice to window grouped streams is to call windowedBy and receive a windowed stream object. The same interface for a windowed stream made from a grouped stream will not work for Cogrouped streams as grouped streams SO we have to make new ones for CogroupedWindows. This is because when a cogroup is created and aggregated the aggregator is associated with each grouped stream then stored in the cogroup. When aggregating what is needed is an initializer but not an aggregator.