Github user alpinegizmo commented on a diff in the pull request:
https://github.com/apache/flink/pull/4041#discussion_r119890353
--- Diff: docs/dev/libs/cep.md ---
@@ -246,63 +334,399 @@ pattern.where(event => ... /* some condition
*/).or(event => ... /* or condition
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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 events:
+
+ 1. Strict Contiguity: which expects all matching events to appear
strictly the one after the other,
+ without any non-matching events in-between.
+
+ 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.
+
+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.
+
+ 2. Relaxed Contiguity: `a1 b` and `a1 a2 b`, as `c` will get simply
ignored.
+
+ 3. Non-Deterministic Relaxed Contiguity: `a1 b`, `a2 b` and `a1 a2 b`.
+
+For looping states (e.g. `oneOrMore()` and `times()`) the default is
*relaxed contiguity*. If you want
+strict contiguity, you have to explicitly specify it by using the
`consecutive()` call, and if you want
+*non-deterministic relaxed contiguity* you can use the
`allowCombinations()` call.
<div class="codetabs" markdown="1">
<div data-lang="java" markdown="1">
+<table class="table table-bordered">
+ <thead>
+ <tr>
+ <th class="text-left" style="width: 25%">Pattern Operation</th>
+ <th class="text-center">Description</th>
+ </tr>
+ </thead>
+ <tbody>
+ <tr>
+ <td><strong>where(condition)</strong></td>
+ <td>
+ <p>Defines a condition for the current state. Only if an
event satisifes the condition,
+ it can match the state. Multiple consecutive where()
clauses lead to their condtions being
+ ANDed:</p>
+{% highlight java %}
+patternState.where(new IterativeCondition<Event>() {
+ @Override
+ public boolean filter(Event value, Context ctx) throws Exception {
+ return ... // some condition
+ }
+});
+{% endhighlight %}
+ </td>
+ </tr>
+ <tr>
+ <td><strong>or(condition)</strong></td>
+ <td>
+ <p>Adds a new condition which is ORed with an existing
one. Only if an event passes one of the
+ conditions, it can match the state:</p>
+{% highlight java %}
+patternState.where(new IterativeCondition<Event>() {
+ @Override
+ public boolean filter(Event value, Context ctx) throws Exception {
+ return ... // some condition
+ }
+}).or(new IterativeCondition<Event>() {
+ @Override
+ public boolean filter(Event value, Context ctx) throws Exception {
+ return ... // alternative condition
+ }
+});
+{% endhighlight %}
+ </td>
+ </tr>
+ <tr>
+ <td><strong>subtype(subClass)</strong></td>
+ <td>
+ <p>Defines a subtype condition for the current pattern
state. Only if an event is of this subtype,
+ it can match the state:</p>
{% highlight java %}
-Pattern<Event, ?> strictNext = start.next("middle");
+patternState.subtype(SubEvent.class);
{% endhighlight %}
+ </td>
+ </tr>
+ <tr>
+ <td><strong>oneOrMore()</strong></td>
+ <td>
+ <p>Specifies that this state expects at least one occurrence
of a matching event.</p>
+ <p>By default a relaxed internal contiguity (between
subsequent events) is used. For more info on the
+ internal contiguity see <a
href="#consecutive_java">consecutive</a></p>
+ {% highlight java %}
+ patternState.oneOrMore();
+ {% endhighlight %}
+ </td>
+ </tr>
+ <tr>
+ <td><strong>times(#ofTimes)</strong></td>
+ <td>
+ <p>Specifies that this state expects an exact number of
occurrences of a matching event.</p>
+ <p>By default a relaxed internal contiguity (between
subsequent events) is used. For more info on the
+ internal contiguity see <a
href="#consecutive_java">consecutive</a></p>
+{% highlight java %}
+patternState.times(2);
+{% endhighlight %}
+ </td>
+ </tr>
+ <tr>
+ <td><strong>optional()</strong></td>
+ <td>
+ <p>Specifies that this pattern is optional, i.e. it may not
occur at all. This is applicable to all
+ aforementioned quantifiers.</p>
+ {% highlight java %}
+ patternState.oneOrMore().optional();
+ {% endhighlight %}
+ </td>
+ </tr>
+ <tr>
+ <td><strong>consecutive()</strong><a
name="consecutive_java"></a></td>
+ <td>
+ <p>Works in conjunction with oneOrMore() and times() and
imposes strict contiguity between the matching
+ events, i.e. any non-matching element breaks the match (as
in next()).</p>
+ <p>If not applied a relaxed contiguity (as in followedBy())
is used.</p>
+
+ <p>E.g. a pattern like:</p>
+ {% highlight java %}
+ Pattern.<Event>begin("start").where(new
SimpleCondition<Event>() {
+ @Override
+ public boolean filter(Event value) throws Exception {
+ return value.getName().equals("c");
+ }
+ })
+ .followedBy("middle").where(new SimpleCondition<Event>() {
+ @Override
+ public boolean filter(Event value) throws Exception {
+ return value.getName().equals("a");
+ }
+ }).oneOrMore().consecutive()
+ .followedBy("end1").where(new SimpleCondition<Event>() {
+ @Override
+ public boolean filter(Event value) throws Exception {
+ return value.getName().equals("b");
+ }
+ });
+ {% endhighlight %}
+ <p>Will generate the following matches for an input
sequence: C D A1 A2 A3 D A4 B</p>
+
+ <p>with consecutive applied: {C A1 B}, {C A1 A2 B}, {C A1 A2
A3 B}</p>
+ <p>without consecutive applied: {C A1 B}, {C A1 A2 B}, {C A1
A2 A3 B}, {C A1 A2 A3 A4 B}</p>
+ </td>
+ </tr>
+ <tr>
+ <td><strong>allowCombinations()</strong><a
name="allow_comb_java"></a></td>
+ <td>
+ <p>Works in conjunction with oneOrMore() and times() and
imposes non-deterministic relaxed contiguity
+ between the matching events (as in followedByAny()).</p>
+ <p>If not applied a relaxed contiguity (as in followedBy) is
used.</p>
+
+ <p>E.g. a pattern like:</p>
+ {% highlight java %}
+ Pattern.<Event>begin("start").where(new
SimpleCondition<Event>() {
+ @Override
+ public boolean filter(Event value) throws Exception {
+ return value.getName().equals("c");
+ }
+ })
+ .followedBy("middle").where(new SimpleCondition<Event>() {
+ @Override
+ public boolean filter(Event value) throws Exception {
+ return value.getName().equals("a");
+ }
+ }).oneOrMore().allowCombinations()
+ .followedBy("end1").where(new SimpleCondition<Event>() {
+ @Override
+ public boolean filter(Event value) throws Exception {
+ return value.getName().equals("b");
+ }
+ });
+ {% endhighlight %}
+ <p>Will generate the following matches for an input
sequence: C D A1 A2 A3 D A4 B</p>
+
+ <p>with combinations enabled: {C A1 B}, {C A1 A2 B}, {C A1
A3 B}, {C A1 A4 B}, {C A1 A2 A3 B}, {C A1 A2 A4 B}, {C A1 A3 A4 B}, {C A1 A2 A3
A4 B}</p>
+ <p>without combinations enabled: {C A1 B}, {C A1 A2 B}, {C
A1 A2 A3 B}, {C A1 A2 A3 A4 B}</p>
+ </td>
+ </tr>
+ </tbody>
+</table>
</div>
<div data-lang="scala" markdown="1">
+<table class="table table-bordered">
+ <thead>
+ <tr>
+ <th class="text-left" style="width: 25%">Pattern Operation</th>
+ <th class="text-center">Description</th>
+ </tr>
+ </thead>
+ <tbody>
+
+ <tr>
+ <td><strong>where(condition)</strong></td>
+ <td>
+ <p>Defines a condition for the current state. Only if an
event satisifes the condition,
+ it can match the state. Multiple consecutive where() clauses
lead to their condtions being
--- End diff --
... can it match the state.
Or turn the sentence around to be more direct:
An event matches the state only if it satisfies the condition.
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