1 / 26

Analysis and Algorithms for Content-based Event Matching

Definition. Content-based matching: publish-subscribe system with attributes associated with each eventExample:stock events with attributes:issuerpricevolume. Background. Mathematical model for content-based pub/sub system: paper by M.K. Aguilera et. al. ?Matching events in a content-based subs

ronli
Download Presentation

Analysis and Algorithms for Content-based Event Matching

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

    1. Analysis and Algorithms for Content-based Event Matching Satyen Kale et. al. Princeton University

    2. Definition Content-based matching: publish-subscribe system with attributes associated with each event Example: stock events with attributes: issuer price volume

    3. Background Mathematical model for content-based pub/sub system: paper by M.K. Aguilera et. al. Matching events in a content-based subscription system Given a publish/subscribe system using content-based matching, we have the following questions: How to match subscribers and events without much a priori information about the events? How about the performance of the algorithm? The proof and correctness for the proposed algorithm? Which algorithm?

    4. Previous Algorithms Two popular matching algorithms Counting-based algorithm This algorithm maintains a counter for each subscription that records the number of its predicates satisfied by the current event Tree-based algorithm This algorithm organizes subscriptions into a rooted search tree We mainly discuss tree-based algorithm which is a foundation of this work

    5. Primitive Algorithm Before Tree Given: attributes A = {a1,a2,,ak} event e subscription sub The primitive algorithm will try to match the event, hence sub(e) = true by testing all attributes Time complexity for N subscriptions: O(kN) Space complexity for N subscriptions: O(kN)

    6. Tree Based Algorithm This algorithm allows pre-processing of the subscriptions before matching an event pre_process(Sub) takes the set of subscriptions Sub and outputs an internal representation of the subscription match(pre_processed_data,event) takes the internal representation and an event, and outputs subscriptions that match the event It aims at reducing time complexity to be sub-linear while keeping the space complexity linear If subscriptions consists of equality test Time complexity is reduced into Lambda depends on the number and type of attributes, 0<lambda<1

    7. Pre-Processing Algorithm This algorithm is used to build the matching tree that will be used in the subsequent event-matching process Components subscription Sub sets of path T (v,r,v) V: an arbitrary node V: an adjacent node r: an edge connecting v to v

    10. Pre-Processing Algorithm for Equality Test This algorithm is used if subscription is determined only by equality tests of the attributes In pseudo code:

    11. Pre-Processing Algorithm for Equality Test

    12. Tree Matching Algorithm Each subscription is a conjunction of elementary predicates An elementary predicate represents one possible result of an elementary test An elementary test is a simple operation on one or more attributes of an event e

    13. Tree Matching Algorithm Example of tree matching

    14. Tree Matching Algorithm Example of tree matching with *-edge *-edge: subscriptions through the edge do not care about the result of a test

    15. General Matching Algorithm Matching algorithm in pseudocode

    16. Matching Equality Tests This test is specialized to match event with only subscription attributes value Each node at the same depth in the tree represents an attribute i

    17. Matching Equality Tests Measuring the complexity: Pre-processing time complexity: O(NK)3, K is a constant -> linear Space complexity: O(NK), K is a constant -> linear Matching time complexity: O(KN1-lambda) -> sub linear

    19. Referred Publish/Subscribe Model There exists a publisher with various topics/events Subscribers can be bound to 3 different states: 1 indicates interest 0 indicates disinterest * indicates dont care The three states is inflicted on each predicate (was named attribute in previous section) of subscription, that is the content of event a subscriber is interested in

    20. Matching problem Given a set of subscription over k predicates p1,p2,,pk and event The matching problem is to identify all subscription in S that e matches

    21. RAPID Match Key concept: In real-world pub/sub applications, many events only have a few relevant properties Simply speaking, the number of 0s outweighs 1s in the properties of an occurring event Definition: c-light event: an event which has at most c 1s in it exactly c-light event: an event which has exactly c 1s in it This algorithm exploits the nature that most events have c<< k (k = total number of attributes in a subscription) -> Zipf distribution

    22. RAPID Match Light Query Model: For parameters (c, alpha) For all t < c, the probability that an event is exactly-t-light event is proportional to t-alpha for some constants alpha>=1. For any t, all exactly-t-light events are equally likely to appear Partitioning the content-space k properties is partitioned into t+1 block with k/(t+1) width

    23. RAPID Match Partitioning example for an exactly-5-light event (t=5)

    24. RAPIDMatch Data Structure

    25. RAPID Match Rapid Match matching algorithm

    26. Implementation Comparing tree-based vs RAPID Match Analyzing the output for arbitrarily created events Improvements?

More Related