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From "Till Rohrmann (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-3318) Add support for quantifiers to CEP's pattern API
Date Wed, 03 Aug 2016 10:11:20 GMT

    [ https://issues.apache.org/jira/browse/FLINK-3318?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15405664#comment-15405664

Till Rohrmann commented on FLINK-3318:

Hi [~ivan.mushketyk],

yes I think we need some API calls which let you specify for a node how often it can appear.
I think you're proposal looks good, but I would not let the quantifier calls take as a parameter
the filter conditions.

Pattern.begin("start").optional().followedBy("next").where(...).times(1, 3).next("end").subtype(...).every()

> Add support for quantifiers to CEP's pattern API
> ------------------------------------------------
>                 Key: FLINK-3318
>                 URL: https://issues.apache.org/jira/browse/FLINK-3318
>             Project: Flink
>          Issue Type: Improvement
>          Components: CEP
>    Affects Versions: 1.0.0
>            Reporter: Till Rohrmann
>            Priority: Minor
> It would be a good addition to extend the pattern API to support quantifiers known from
regular expressions (e.g. Kleene star, ?, +, or count bounds). This would considerably enrich
the set of supported patterns.
> Implementing the count bounds could be done by unrolling the pattern state. In order
to support the Kleene star operator, the {{NFACompiler}} has to be extended to insert epsilon-transition
between a Kleene start state and the succeeding pattern state. In order to support {{?}},
one could insert two paths from the preceding state, one which accepts the event and another
which directly goes into the next pattern state.

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