title: Iteration over multiple streams in Apache Flink
body: <p>My Question in regarding iteration over multiple streams in Apache Flink.</p>
  
  <p>I am a Flink beginner, and I am currently trying to execute a recursive query (e.g., datalog) on Flink. </p>
  
  <p>For example, a query calculates the transitive closure for every 5mins (tumbling window). If I have one input stream inputStream (consists of initial edge informations), another outputStream (the transitive closure) which is initialised by the inputStream. And I want to iteratively enrich the outputStream by joining the inputStream. For each iteration, the feedback should be the outputStream, and the iteration will last until no more edge can be appended on outputStream. The computation of my transitive closure should trigger periodically for every 5 mins. During the iteration, the inputStream should be "hold" and provide the data for my outputStream.</p>
  
  <p>Is it possible to do this in Flink? Thanks for any help!</p>