Kalavri | Boston University 2020 Stream denotation An abstract interpretation of the stream as a mathematical structure, e.g. a sequence of (finite) relation states over a common schema R: [r1(R), r2(R)

ε)*Ν δ*Ν not included may be included included ??? Vasiliki Kalavri | Boston University 2020 Notation (I) Input: a stream of items N: number of items in the stream fe: true frequency of the item No item with frequency less than (δ-ε)*N. 5 ??? Vasiliki Kalavri | Boston University 2020 Notation (II) • We define windows of size w = 1/ε with increasing numeric ids, starting from 1. • e

subscribing to all sub-topics of that topic, too. • Topic names are represented with URL-like notation and some systems also allow the use of wildcards. 21 Content-based Pub/Sub • Events are grouped