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From fhueske <...@git.apache.org>
Subject [GitHub] flink pull request #3191: [FLINK-5529] [FLINK-4752] [docs] Improve / extends...
Date Thu, 26 Jan 2017 16:32:14 GMT
Github user fhueske commented on a diff in the pull request:

    https://github.com/apache/flink/pull/3191#discussion_r98026721
  
    --- Diff: docs/dev/windows.md ---
    @@ -692,30 +708,39 @@ input
     
     ## Triggers
     
    -A `Trigger` determines when a window (as formed by the `WindowAssigner`) is ready to
be
    +A `Trigger` determines when a window (as formed by the *window assigner*) is ready to
be
     processed by the *window function*. Each `WindowAssigner` comes with a default `Trigger`.

     If the default trigger does not fit your needs, you can specify a custom trigger using
`trigger(...)`.
     
    -The trigger interface provides five methods that react to different events: 
    +The trigger interface has five methods that allow a `Trigger` to react to different events:
     
     * The `onElement()` method is called for each element that is added to a window. 
     * The `onEventTime()` method is called when  a registered event-time timer fires. 
     * The `onProcessingTime()` method is called when a registered processing-time timer fires.

     * The `onMerge()` method is relevant for stateful triggers and merges the states of two
triggers when their corresponding windows merge, *e.g.* when using session windows. 
     * Finally the `clear()` method performs any action needed upon removal of the corresponding
window. 
     
    -Any of these methods can be used to register processing- or event-time timers for future
actions. 
    +Two things to notice about the above methods are:
    +
    +1) The first three can return a `TriggerResult`, *i.e.* take action as a response to
their corresponding event. The action can be one of the following: 
    --- End diff --
    
    "The first three decide how to act on their invocation event by returning a `TriggerResult`."


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