Lecture 16 Probabilistic Databases Slides by Gerome Miklau

Lecture 16: Probabilistic Databases Slides by Gerome Miklau Based on a tutorial by Dan Suciu 1

Today’s Agenda 1. Motivation 2. Probabilistic Data Semantics 3. Representation Systems 4. Complexity 2

Section 1 1. Motivation 3

Section 1 Motivating Applications • Text extraction & record linkage • Inconsistent data • Ranking query answers 4

Section 1 Text extraction 5

Section 1 Record Linkage 6

Section 1 Inconsistent Data • Goal: consistent query answers from inconsistent databases • Applications: • Integration of autonomous data sources • Un-enforced integrity constraints • Temporary inconsistencies 7

Section 1 Repair semantics 8

Section 1 Alternative probabilistic approach 9

Section 1 Ranking query answers • Database is deterministic • Query answers are uncertain: • Query terms loosened due to user’s lack of understanding of the data or schema • The query returns a ranked list of tuples; user interested in top-k 10

Section 1 Summary: motivating applications 11

Section 2 2. Probabilistic Data Semantics 12

Section 2 Possible worlds semantics 13

Section 2 The definition 14

Section 2 Example 15

Section 2 Tuples as Events 16

Section 2 Tuple correlation 17

Section 2 Example 18

Section 2 Query semantics 19

Section 2 Query semantics 20

Section 2 Example: Query Semantics 21

Section 2 Query semantics 22

Section 3 3. Representation Systems 23

Section 3 Representation systems 24

Section 3 Representation systems 25

Section 3 Tuple independent probabilistic database 26

Section 3 Tuple Prob. -> Possible Worlds 27

Section 3 Tuple Prob. -> Query evaluation 28

Section 3 Tuple-independent distributions 29

Section 3 Intensional database 30

Section 3 Intensional DB => Possible Worlds 31

Section 3 Possible Worlds => Intensional DB 32

Section 3 Closure under operators 33

Section 3 Summary of Intensional Databases 34

Section 4 4. Complexity 35

Section 4 Probability of boolean expressions 36

Section 4 Example 37

Section 4 Complexity of Boolean Expression Probability 38

Section 4 Query complexity 39

Section 4 Intensional query evaluation 40

Section 4 Extensional query evaluation 41

Section 4 42

Section 4 Query complexity 43

Section 4 Summary on query complexity 44