Linked Data on the Web
Query Processing ∙ Trustworthiness
Olaf Hartig

What is
linked data
?
2
Query Processing and Trustworthiness in the Web of Linked Data (Olaf Hartig)

The classic Web:
Data exposed
to the Web
via HTML
CIA World
MovieDB
Factbook
3
Query Processing and Trustworthiness in the Web of Linked Data (Olaf Hartig)

The classic Web:
Information from
single pages
can be found via
search engines
4
Query Processing and Trustworthiness in the Web of Linked Data (Olaf Hartig)

The classic Web:
How about complex queries over
multiple pages / data sources?
What documentaries
are filmed in countries with an
unemployment rate above 10%?
Impossible.
5
Query Processing and Trustworthiness in the Web of Linked Data (Olaf Hartig)

What do we actually want?
Use the Web like a
single global database
CIA World
MovieDB
Factbook
6
Query Processing and Trustworthiness in the Web of Linked Data (Olaf Hartig)

Linked data enables such a
Web of data
CIA World
MovieDB
Factbook
7
Query Processing and Trustworthiness in the Web of Linked Data (Olaf Hartig)

Linked data enables such a
Web of data
Global Identifier: URI
http://...imdb.../genres/Documentary
http://cia..../Albania
http://...imdb.../data/WarChildDocu
CIA World
MovieDB
Factbook
8
Query Processing and Trustworthiness in the Web of Linked Data (Olaf Hartig)

Linked data enables such a
Web of data
Global Identifier: URI
Data Model: RDF
http://...imdb.../genres/Documentary
\"War Child\"
http://cia..../Albania http://.../genre
http://.../name
http://.../unemp_rate
http://...imdb.../data/WarChildDocu
13.2 %
CIA World
MovieDB
Factbook
9
Query Processing and Trustworthiness in the Web of Linked Data (Olaf Hartig)

Linked data enables such a
Web of data
Global Identifier: URI
Data Model: RDF
Access Mechanism: HTTP http://...imdb.../genres/Documentary
\"War Child\"
http://cia..../Albania http://.../genre
http://.../name
http://.../unemp_rate
http://...imdb.../data/WarChildDocu
13.2 %
CIA World
MovieDB
Factbook
10
Query Processing and Trustworthiness in the Web of Linked Data (Olaf Hartig)

Linked data enables such a
Web of data
Global Identifier: URI
Data Model: RDF
Access Mechanism: HTTP http://...imdb.../genres/Documentary
Connection: Typed Links
\"War Child\"
http:
http://cia..../Albania http://.../genre
//.../f
ilmin
http://.../name
g_lo
catio
http://.../unemp_rate n
http://...imdb.../data/WarChildDocu
13.2 %
CIA World
MovieDB
Factbook
11
Query Processing and Trustworthiness in the Web of Linked Data (Olaf Hartig)

Linked data enables such a
Web of data
Global Identifier: URI
What documentaries
Data Model: RDF
are filmedMechanism: HTTP http://...imdb.../genres/Documentary
Access in countries with an
unemployment rate Links
Connection: Typed above 10%?
\"War Child\"
http:
http://cia..../Albania http://.../genre
//.../f
ilmin
http://.../name
g_lo
catio
http://.../unemp_rate n
http://...imdb.../data/WarChildDocu
13.2 %
CIA World
MovieDB
Factbook
12
Query Processing and Trustworthiness in the Web of Linked Data (Olaf Hartig)

How do we
query the whole
Web of linked data
efficiently?
13
Query Processing and Trustworthiness in the Web of Linked Data (Olaf Hartig)

Contribution (I):
Efficient query
processing in the
Web of data
14
Query Processing and Trustworthiness in the Web of Linked Data (Olaf Hartig)

http://...imdb.../InBetweenMovie http://.../filming_location ?country .
http://.../unemp_rate
?country ?u .
Query
http://cia..../Albania
http://...imdb.../genres/Drama
htt
p:
/ /. .
./fi
lm
in g
\"In Between\"
_lo
ca http://.../genre
tio
n
http://.../name
http://.../fil
http://cia..../Canada ming_loca
tion
http://...imdb.../data/InBetweenMovie
Data
15
Query Processing and Trustworthiness in the Web of Linked Data (Olaf Hartig)

http://...imdb.../InBetweenMovie http://.../filming_location ?country .
http://.../unemp_rate
?country ?u .
Query
http://cia..../Albania
http://...imdb.../genres/Drama
htt
p:
/ /. .
./fi
lm
in g
\"In Between\"
_lo
ca http://.../genre
tio
n
http://.../name
http://.../fil
http://cia..../Canada ming_loca
tion
http://...imdb.../data/InBetweenMovie
Data
Challenge: Intermediate results drive the
discovery of further, potentially relevant data
16
Query Processing and Trustworthiness in the Web of Linked Data (Olaf Hartig)

http://...imdb.../InBetweenMovie http://.../filming_location ?country .
http://.../unemp_rate
?country ?u .
Query
http://cia..../Albania
http://...imdb.../genres/Drama
htt
p:
http://.../unemp_rate / /. .
./fi
lm
in g
13.2 % \"In Between\"
_lo
ca http://.../genre
tio
n
http://.../name
http://.../fil
http://cia..../Canada ming_loca
tion
http://...imdb.../data/InBetweenMovie
http://.../unemp_rate
6%
Data
Challenge: Intermediate results drive the
discovery of further, potentially relevant data
17
Query Processing and Trustworthiness in the Web of Linked Data (Olaf Hartig)

Is the data
trustworthy?
18
Query Processing and Trustworthiness in the Web of Linked Data (Olaf Hartig)

Contribution (II):
Trustworthiness in
the Web of data
Representing ∙ Determining ∙ Accessing
19
Query Processing and Trustworthiness in the Web of Linked Data (Olaf Hartig)

What is trustworthy Web data?
Trustworthiness of RDF statements
is the subjective belief or disbelief
in the truth of the statements.
20
Query Processing and Trustworthiness in the Web of Linked Data (Olaf Hartig)

What is trustworthy Web data?
Trustworthiness of RDF statements
is the subjective belief or disbelief
in the truth of the statements.
uncertainty
disbelief belief
-1 0 1
21
Query Processing and Trustworthiness in the Web of Linked Data (Olaf Hartig)

http://...imdb.../genres/Documentary
\"War Child\"
http:
http://cia..../Albania http://.../genre
/ / . . ./ f
ilmin
http://.../name
g_lo
catio
http://.../unemp_rate n
http://...imdb.../data/WarChildDocu
13.2 %
22
Query Processing and Trustworthiness in the Web of Linked Data (Olaf Hartig)

http://...imdb.../genres/Documentary
\"War Child\"
http:
http://cia..../Albania http://.../genre
/ / . . ./ f
ilmin
http://.../name
g_lo
catio
http://.../unemp_rate n
http://...imdb.../data/WarChildDocu
13.2 %
TrustFct
23
Query Processing and Trustworthiness in the Web of Linked Data (Olaf Hartig)

http://...imdb.../genres/Documentary
\"War Child\"
http:
http://cia..../Albania http://.../genre
/ / . . ./ f
ilmin
http://.../name
g_lo
catio
http://.../unemp_rate n
http://...imdb.../data/WarChildDocu
13.2 %
TrustFct( )
http://cia..../Albania
http://.../unemp_rate
13.2 %
24
Query Processing and Trustworthiness in the Web of Linked Data (Olaf Hartig)

http://...imdb.../genres/Documentary
\"War Child\"
http:
http://cia..../Albania http://.../genre
/ / . . ./ f
ilmin
http://.../name
g_lo
catio
http://.../unemp_rate n
http://...imdb.../data/WarChildDocu
13.2 %
TrustFct( ,)
http://cia..../Albania
http://.../unemp_rate
13.2 %
25
Query Processing and Trustworthiness in the Web of Linked Data (Olaf Hartig)

http://...imdb.../genres/Documentary
\"War Child\"
http:
http://cia..../Albania http://.../genre
/ / . . ./ f
ilmin
http://.../name
g_lo
catio
http://.../unemp_rate n
[0.8] http://...imdb.../data/WarChildDocu
13.2 %
TrustFct( , ) = 0.8
http://cia..../Albania
http://.../unemp_rate
13.2 %
26
Query Processing and Trustworthiness in the Web of Linked Data (Olaf Hartig)

Trust assessment
strategies
User-based 3 Party-based
rd
Provenance-based
27
Query Processing and Trustworthiness in the Web of Linked Data (Olaf Hartig)

Trust requirements in queries:
http://...imdb.../InBetweenMovie http://.../filming_location ?country .
Query
Data
http://cia..../China
htt
p: //
. .. /f
il m
[- 0.7] i ng
_lo
http:
http://cia..../Albania //.../fi catio
lming n
_loca
tion
[0.8]
http://...imdb.../data/InBetweenMovie
cation
_lo
ilming
./f
ttp://..
h
[0.68]
http://cia..../Canada
28
Query Processing and Trustworthiness in the Web of Linked Data (Olaf Hartig)

Trust requirements in queries:
http://...imdb.../InBetweenMovie http://.../filming_location ?country .
[0.5 , 1.0]
Query
Data
http://cia..../China
htt
p: //
. .. /f
il m
[- 0.7] i ng
_lo
http:
http://cia..../Albania //.../fi catio
lming n
_loca
tion
[0.8]
http://...imdb.../data/InBetweenMovie
cation
_lo
ilming
./f
ttp://..
h
[0.68]
http://cia..../Canada
29
Query Processing and Trustworthiness in the Web of Linked Data (Olaf Hartig)

Trust requirements in queries:
http://...imdb.../InBetweenMovie http://.../filming_location ?country .
[0.5 , 1.0]
Query
Data
http://cia..../China
htt
p: //
. .. /f
il m
[- 0.7] i ng
_lo
http:
http://cia..../Albania //.../fi catio
lming n
_loca
tion
[0.8]
http://...imdb.../data/InBetweenMovie
cation
_lo
ilming
./f
ttp://..
h
[0.68]
http://cia..../Canada
30
Query Processing and Trustworthiness in the Web of Linked Data (Olaf Hartig)

Thank you!
31
Query Processing and Trustworthiness in the Web of Linked Data (Olaf Hartig)

Attribution:
http://www.flickr.com/photos/mrfaber/247946146/
www.opte.org
http://www.flickr.com/photos/hartkopf/1586832162/
32
Query Processing and Trustworthiness in the Web of Linked Data (Olaf Hartig)