[jira] [Created] (FLINK-5375) Fix watermark documentation

[Shang Yuanchun (Jira)]

Fabian Hueske created FLINK-5375:
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             Summary: Fix watermark documentation
                 Key: FLINK-5375
                 URL: https://issues.apache.org/jira/browse/FLINK-5375
             Project: Flink
          Issue Type: Bug
          Components: Documentation, Project Website
    Affects Versions: 1.1.3, 1.2.0, 1.3.0
            Reporter: Fabian Hueske
            Priority: Critical
             Fix For: 1.2.0, 1.1.4, 1.3.0


The [documentation of watermarks|https://ci.apache.org/projects/flink/flink-docs-release-1.2/dev/event_time.html#event-time-and-watermarks] is not correct. It states

{quote}
A Watermark(t) declares that event time has reached time t in that stream, meaning that all events with a timestamps t’ < t have occurred.
{quote}

whereas the JavaDocs which is aligned with implementation says

{quote}
A Watermark tells operators that receive it that no elements with a
timestamp older or equal to the watermark timestamp should arrive at the
operator.
{quote}

The documentation needs to be updated. Moreover, we need to carefully check that the watermark semantics are correctly described in other pages of the documentation and blog posts published on the Flink website.





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