[jira] [Commented] (FLINK-3318) Add support for quantifiers to CEP's pattern API

["Ivan Mushketyk (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-3318?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15405429#comment-15405429 ] 

Ivan Mushketyk commented on FLINK-3318:
---------------------------------------

Hi,

Do you mean something like this:

Pattern.begin("start")
  .oneOrMore(where(...).subtype(SubEvent.class)) // + operator
  .followedBy("next").optional(where(...).subtype(...)) // ? operator
  .next("end").count(1, 3).(where(...)) // count bounds operator

If no one is working on this and you like the idea, I can give it a try.

> 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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