RDF Seminar Presentation

RDF Triple Stores,
SPARQL and the
Semantic Web
Presented By: Supervised By:
Muntazir Mehdi Dipl.-Inf. Andreas M. Weiner

1

Overview
• A little about Semantic Web
• RDF structure and syntax
• SPARQL structure and syntax
• Data Management & Storage
• Sesame’s Architecture
• Vertically Partitioned Approach
• RDF-3X

• Summary

2

Web today
• Invented by Sir Tim B. Lee (1989)
• Network of unspecified links between web pages
• Problem : Only humans can process information in a
meaningful way

WP2 WP4

WP1 WP3

3

The Semantic Web
• Semantic := “Meaning of linguistic terms”
• Coined by Sir Tim B. Lee (1997)
• Web of content, Semantic relations between web
pages
• Machines can process content
“The Semantic Web is extension of current Web in
which information is given well-defined meaning,
better enabling computers and people to work in co-
operation”
Ref: Tim B. Lee, J. Hendler, O. Lassila
“The Semantic Web”, Scientific American, May 2001

4

Goal of Semantic Web
“The Semantic Web will bring structure to the
meaningful content of web pages, creating an
environment where software agents roaming from
page to page can readily carry out sophisticated
tasks for users.”
“Properly designed, the Semantic Web can assist in
the evolution of human knowledge as a whole.”
Ref: Tim B. Lee, J. Hendler, O. Lassila
“The Semantic Web”, Scientific American, May 2001

WHAT? WHERE? WHEN?

5

Semantic Web Layers

6

Information
Representation
• Using XML
• Advantage: A lot of parsers and validators are
available
• But: A single domain of knowledge can be coded
with multiple possibilities.
• Solution:
“Resource Description Framework (RDF) is a
framework and standard data interchange model
belonging to the family of World Wide Web
Consortium (W3C) for modeling and representing
information”
Ref: Graham Klyne, Jeremy J. Carroll, Brian McBride.
Resource Description Framework (RDF): Concepts and Abstract Syntax, W3C
Recommendation. 2004.
7

Resource Description
Framework (RDF)

• Two parts of RDF:
• RDF Model
a set of statements := triples, directed graphs
• RDF Syntax
Serialization of RDF as XML

8

RDF Model
• Statement
“Technical University Kaiserslautern is located in
Kaiserslautern”
• Triple
<TU Kaiserslautern><isLocatedIn><Kaiserslautern>

• Directed Graph

9

RDF Model (cont.)
• Some more statements:

“Technical University Kaiserslautern is located in Kaiserslautern”
“University of Kaiserslautern was founded in July, 1970”
“Kaiserslautern University has a department of Computer Science”

• Problem: Many names of one resource
• Solution: Identification (URI)
• RDF Terminology:
o Subject (Resource)
o Predicate (Property)
o Object (Value)

10

RDF Model: An example

11

SPARQL: Query language
for RDF
• Recursive acronym for SPARQL Protocol and RDF
Query Language
• Queries may contain triple patterns, conjunctions,
disjunctions and optional patterns
• Available since 2008 as W3C Recommendation
• Query Forms:
o SELECT: return value of mapped variable in a pattern
o ASK: returns Boolean value with respect to the query match
o CONSTRUCT: returns graph by substituting value
o DESCRIBE: returns graph of a match

13

SPARQL: An example
• Query

• Output

14

Sesame’s Architecture
• Open source standard framework for RDF data processing;
storing, querying and reasoning
• Implementation on:

15

Sesame’s Functional
Modules
• Query Module

• Admin Module
o Incrementally add RDF(S) data
o Cleaning up repository

• RDF Export Module
o Exports RDF(S) data/schema/both as serialized XML

16

Vertically partitioned
approach

18

RDF-3X
• 3 Salient features of RDF-3X:

1. A Storage implementation for RDF which requires
no further tuning

2. A query processor

3. A query optimizer

19

Summary
• A shift from syntactic to semantic web
• Representation of information with RDF
• SPARQL for querying RDF data
• Storage mechanisms and RDF data management

20

Thank you for your
attention!

21

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