1. Lu Xing
CS59000GDM
Sept 7th, 2018

2. Knowledge Graph
The Knowledge Graph is a knowledge base used by Google and its services to enhance its search engine's results with information gathered from a variety of sources.

3. Soccer player 30 million EUR Juventus Feb 5th, 1985 Cristiano Ronaldo
Funchal, Portugal
6’2’’
Soccer player
Juventus
Current team
Occupation
Salary
Birth date
Birth place
Height

5. RDF Resource Description Framework
It is a family of World Wide Web Consortium (W3C) specifications originally designed as a metadata data model.
Subject
Object
Predicate

6. Subject: URI or a blank node, both of which denote resources
Object
Predicate
Subject: URI or a blank node, both of which denote resources
Predicate: URI
Object: URI, blank node or a Unicode string literal.
URI: uniform resource identifier, a string of characters designed for unambiguous identification of resources and extensibility via the URI scheme.

7. SPARQL
SPARQL Protocol and RDF Query Language
Graphical queries

8. How to find a matched pattern in a RDF graph?
RDF indexing!

9. Idea in a high level Identify certain centers in the graph
Propose a notion of radius from these center vertices
Associate vertices within the radius of the center
Define a tree data structure to store the regions specified by the centers

19. GRIN index

21. Query Evaluation
Graphical query q = (N,V,E,λn)  derive inequality constraints
For any path of length l on edges from Es connecting a resource c and a variable v, we write d(c, v) ≤ l. The rule applies similarly for paths from v to c.
For any edge (c, v, P, l) ∈ Ed, we write d(λn(c), λn(v)) ≤ l. The rule applies similarly for edges from v to c.

22. Two rules for rejection
Rule 1: for any constant (resource) x in q, reject (c, r) if d(c, x) > z (?)
Rule 2: if there exists v ∈ V such that (c, r) does not definitely satisfy v, then reject (c, r)

24. Compared to other work

25. Drawbacks? (from other groups)
It focuses more on path-like queries on RDF data
It shows good performance on small- to medium sized data and for hand-specified execution plans.
It entails difficult optimization problems of identifying the most beneficial paths.

26. Thank you!

27. Before building the index…
M: the maximum number of RDF graph vertices per page
C: the number of leaf nodes
|R|: the number of resources and literals
|R| / C ≤ M ⇒ C ≥ |R| / M .