Github user dawidwys commented on a diff in the pull request:
https://github.com/apache/flink/pull/4041#discussion_r119611549
--- Diff: docs/dev/libs/cep.md ---
@@ -246,63 +333,118 @@ pattern.where(event => ... /* some condition
*/).or(event => ... /* or condition
</div>
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-Next, we can append further states to detect complex patterns.
-We can control the contiguity of two succeeding events to be accepted by
the pattern.
+##### Conditions on Contiguity
-Strict contiguity means that two matching events have to be directly the
one after the other.
-This means that no other events can occur in between.
-A strict contiguity pattern state can be created via the `next` method.
+FlinkCEP supports the following forms of contiguity between consecutive
events:
-<div class="codetabs" markdown="1">
-<div data-lang="java" markdown="1">
-{% highlight java %}
-Pattern<Event, ?> strictNext = start.next("middle");
-{% endhighlight %}
-</div>
+ 1. Strict Contiguity: which expects all matching events to appear
strictly the one after the other,
+ without any non-matching events in-between.
-<div data-lang="scala" markdown="1">
-{% highlight scala %}
-val strictNext: Pattern[Event, _] = start.next("middle")
-{% endhighlight %}
-</div>
-</div>
+ 2. Relaxed Contiguity: which simply ignores non-matching events appearing
in-between the matching ones.
+
+ 3. Non-Deterministic Relaxed Contiguity: which further relaxes contiguity
by also creating alternative
+ matches which ignore also matching events.
-Non-strict contiguity means that other events are allowed to occur
in-between two matching events.
-A non-strict contiguity pattern state can be created via the `followedBy`
or `followedByAny` method.
+To illustrate the above with an example, a pattern sequence `a+ b` (one or
more `a`s followed by a `b`) with
+input `a1, c, a2, b` will have the following results:
+
+ 1. Strict Contiguity: `a2 b` because there is `c` `a1` and `a2` so `a1`
is discarded.
--- End diff --
there is `c` between `a1` and `a2`
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