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From "Kenneth Knowles (JIRA)" <>
Subject [jira] [Updated] (BEAM-101) Data-driven triggers
Date Fri, 04 Nov 2016 18:07:58 GMT


Kenneth Knowles updated BEAM-101:
    Summary: Data-driven triggers  (was: Support data-driven triggers)

> Data-driven triggers
> --------------------
>                 Key: BEAM-101
>                 URL:
>             Project: Beam
>          Issue Type: New Feature
>          Components: beam-model
>            Reporter: Robert Bradshaw
>            Assignee: Frances Perry
> For some applications, it's useful to declare a pane/window to be emitted (or finished)
based on its contents. The simplest of these is the AfterCount trigger, but more sophisticated
predicates could be constructed.
> The requirements for consistent trigger firing are essentially that the state of the
trigger form a lattice and that the "should fire?" question is a monotonic predicate on the
lattice. Basically it asks "are we high enough up the lattice?"
> Because the element types may change between the application of Windowing and the actuation
of the trigger, one idea is to extract the relevant data from the element at Windowing and
pass it along implicitly where it can be combined and inspected in a type safe way later (similar
to how timestamps and windows are implicitly passed with elements).

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