These are the slides from my WWW 2013 Tutorial "Linked Data Query Processing" http://db.uwaterloo.ca/LDQTut2013/

1. Linked Data Query Processing
Tutorial at the 22nd International World Wide Web Conference (WWW 2013)
May 14, 2013
http://db.uwaterloo.ca/LDQTut2013/
4. Execution Process
Olaf Hartig
University of Waterloo

2. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 2
Outline
 Separated Execution
 Integrated Execution
➢ General Idea and Properties
➢ Push-Based Implementation [LT10, LT11]
➢ Link Traversal Based Query Execution

3. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 3
… clearly separate
data retrieval
and
result construction
into two
consecutive phases
Separated Execution Approaches
Query-local data
http://mdb.../Paul http://geo.../Berlin
http://mdb.../Ric http://geo.../Rome
?loc?actor
GET http://.../movie2449
1
2

4. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 4
Properties of Separated Execution
Query-local data
http://mdb.../Paul http://geo.../Berlin
http://mdb.../Ric http://geo.../Rome
?loc?actor
GET http://.../movie2449
1
2
● Advantage: straightforward to implement
● Can be combined with any
source selection strategy
● A traditional query execution
plan might then be used for
constructing the result
● Downside: First solutions cannot
be reported before data retrieval
has been completed

5. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 5
Query-local data
http://mdb.../Paul http://geo.../Berlin
http://mdb.../Ric http://geo.../Rome
?loc?actor
GET http://.../movie2449
Integrated Execution Approaches
… intertwine
data retrieval and
result construction

6. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 6
Query-local data
http://mdb.../Paul http://geo.../Berlin
http://mdb.../Ric http://geo.../Rome
?loc?actor
GET http://.../movie2449
Integrated Execution Approaches
● Implementations may report
first solutions early
● For monotonic queries
● Implementations may process
data in a streaming manner
● May require less query-local
memory (b/c query-local dataset
need not be materialized)
● Can also be combined with any
source selection strategy
… intertwine
data retrieval and
result construction

7. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 7
Outline
 Separated Execution
 Integrated Execution
➢ General Idea and Properties
➢ Push-Based Implementation [LT10, LT11]
➢ Link Traversal Based Query Execution
√
√

8. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 8
Push-Based Implementation
TP Operator TP Operator
TP Operator
Join
Operator
Join
Operator
● Each operator runs as an
asynchronous thread
● Connected via
message queues
Data Retrieval
Operator

9. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 9
Push-Based Implementation
TP Operator TP Operator
TP Operator
Join
Operator
Join
Operator
● Each operator runs as an
asynchronous thread
● Connected via
message queues
● Data retrieval operator
● May apply any possible
source selection strategy
● Usually, implemented via
multiple lookup threads
● Pushes any incoming
matching triple to the
corresponding triple
pattern operator
Data Retrieval
Operator

10. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 10
Push-Based Implementation (Example)
TP Operator
( ?p, interested in, ?i )
TP Operator
( ?p, affiliated with, orgax )
TP Operator
( ?i, rdf:type, Book )
Join
Operator
Join
Operator
Data Retrieval
Operator

11. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 11
Push-Based Implementation (Example)
TP Operator
( ?p, interested in, ?i )
TP Operator
( ?p, affiliated with, orgax )
TP Operator
( ?i, rdf:type, Book )
Join
Operator
Join
Operator
Data Retrieval
Operator
{ ?p → alice }
( alice, affiliated with, orgax )
( alice, affiliated with, orgax )

12. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 12
Push-Based Implementation (Example)
TP Operator
( ?p, interested in, ?i )
TP Operator
( ?p, affiliated with, orgax )
TP Operator
( ?i, rdf:type, Book )
Join
Operator
Join
Operator
Data Retrieval
Operator
{ ?p → alice }
( alice, interested in, yoga )
{ ?p → alice, ?i → yoga }
( alice, interested in, yoga )
{ ?p → alice, ?i → yoga }

13. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 13
Symmetric Hash Join (SHJ)
SHJ Operator
# Bucket
1 {?p → alice,?i → yoga}
2
3 {?p → bob,?i → tea}, {?p → bob,?i → chess}
# Bucket
1 {?p → alice,?o → orgax}
2 {?p → eve,?o → orgax}
3
● Maintains a hash table for each input
● Same hash function for both tables
● Each bucket contains a set of input solutions

14. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 14
How SHJ Processes Incoming Solution
SHJ Operator
# Bucket
1 {?p → alice,?i → yoga}
2
3 {?p → bob,?i → tea}, {?p → bob,?i → chess}
# Bucket
1 {?p → alice,?o → orgax}
2 {?p → eve,?o → orgax}
3
● Hash the value that μinput binds to the join variable
μinput = {?p → bob,?o → acme}

15. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 15
How SHJ Processes Incoming Solution
SHJ Operator
# Bucket
1 {?p → alice,?i → yoga}
2
3 {?p → bob,?i → tea}, {?p → bob,?i → chess}
# Bucket
1 {?p → alice,?o → orgax}
2 {?p → eve,?o → orgax}
3
● Hash the value that μinput binds to the join variable
● Insert μinput into the corresponding input hash table
hfct(bob) = 3μinput = {?p → bob,?o → acme}

16. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 16
How SHJ Processes Incoming Solution
SHJ Operator
# Bucket
1 {?p → alice,?i → yoga}
2
3 {?p → bob,?i → tea}, {?p → bob,?i → chess}
# Bucket
1 {?p → alice,?o → orgax}
2 {?p → eve,?o → orgax}
3 {?p → bob,?o → acme}
● Hash the value that μinput binds to the join variable
● Insert μinput into the corresponding input hash table
● Probe into the other hash table to find join candidates
● Merge μinput with each join candidate, push results to output
{?p → bob,?o → acme,?i → tea}
hfct(bob) = 3
{?p → bob,?o → acme,?i → chess}
μinput = {?p → bob,?o → acme}

17. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 17
Outline
 Separated Execution
 Integrated Execution
➢ General Idea and Properties
➢ Push-Based Implementation [LT10, LT11]
➢ Link Traversal Based Query Execution
√
√
√

18. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 18
Link Traversal Based Query Execution
… is the combination of
integrated execution and
live exploration
(i.e., the push-based approach can be
used as an implementation of LTBQE)
An even closer combination presents the
following pull-based implementation approach ...

19. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 19
?p ex:affiliated_with <http://.../orgaX>
?p ex:interested_in ?b
?b rdf:type <http://.../Book>
Query
Seed: <http://.../orgaX>
Pipeline of Link Traversing Iterators
I3
I2
I1

20. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 20
?p ex:affiliated_with <http://.../orgaX>
?p ex:interested_in ?b
?b rdf:type <http://.../Book>
Query
tp1
= ( ?p , ex:affiliated_with , <http://.../orgaX> ) I1
tp2
= ( ?p , ex:interested_in , ?b ) I2
tp3
= ( ?b , rdf:type , <http://.../Book> ) I3
Seed: <http://.../orgaX>
Pipeline of Link Traversing Iterators

21. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 21
?p ex:affiliated_with <http://.../orgaX>
?p ex:interested_in ?b
?b rdf:type <http://.../Book>
Query
Seed: <http://.../orgaX>
tp1
= ( ?p , ex:affiliated_with , <http://.../orgaX> ) I1
tp2
= ( ?p , ex:interested_in , ?b ) I2
tp3
= ( ?b , rdf:type , <http://.../Book> ) I3
query-local
dataset
Pipeline of Link Traversing Iterators

22. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 22
?p ex:affiliated_with <http://.../orgaX>
?p ex:interested_in ?b
?b rdf:type <http://.../Book>
Query
Seed: <http://.../orgaX>
tp1
= ( ?p , ex:affiliated_with , <http://.../orgaX> ) I1
tp2
= ( ?p , ex:interested_in , ?b ) I2
tp3
= ( ?b , rdf:type , <http://.../Book> ) I3
query-local
dataset
Pipeline of Link Traversing Iterators

23. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 23
?p ex:affiliated_with <http://.../orgaX>
?p ex:interested_in ?b
?b rdf:type <http://.../Book>
Query
Seed: <http://.../orgaX>
tp1
= ( ?p , ex:affiliated_with , <http://.../orgaX> ) I1
tp2
= ( ?p , ex:interested_in , ?b ) I2
tp3
= ( ?b , rdf:type , <http://.../Book> ) I3
query-local
dataset
Pipeline of Link Traversing Iterators

24. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 24
query-local
dataset
Next?
tp1
= ( ?p , ex:affiliated_with , <http://.../orgaX> ) I1
tp2
= ( ?p , ex:interested_in , ?b ) I2
tp3
= ( ?b , rdf:type , <http://.../Book> ) I3
Pipeline of Link Traversing Iterators

25. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 25
query-local
dataset
Next?
Next?
tp1
= ( ?p , ex:affiliated_with , <http://.../orgaX> ) I1
tp2
= ( ?p , ex:interested_in , ?b ) I2
tp3
= ( ?b , rdf:type , <http://.../Book> ) I3
Pipeline of Link Traversing Iterators

26. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 26
query-local
dataset
Next?
Next?
Next?
tp1
= ( ?p , ex:affiliated_with , <http://.../orgaX> ) I1
tp2
= ( ?p , ex:interested_in , ?b ) I2
tp3
= ( ?b , rdf:type , <http://.../Book> ) I3
Pipeline of Link Traversing Iterators

27. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 27
Next?
Next?
Next?
tp2
= ( ?p , ex:interested_in , ?b ) I2
tp3
= ( ?b , rdf:type , <http://.../Book> ) I3
tp1
= ( ?p , ex:affiliated_with , <http://.../orgaX> ) I1
:
<http://.../alice> ex:affiliated_with <http://.../orgaX>
:
query-local
dataset
Pipeline of Link Traversing Iterators

28. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 28
Next?
tp1
= ( ?p , ex:affiliated_with , <http://.../orgaX> ) I1
:
<http://.../alice> ex:affiliated_with <http://.../orgaX>
:
query-local
dataset
{ ?p = <http://.../alice> }
Next?
tp2
= ( ?p , ex:interested_in , ?b ) I2
tp3
= ( ?b , rdf:type , <http://.../Book> ) I3
Pipeline of Link Traversing Iterators

29. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 29
tp1
= ( ?p , ex:affiliated_with , <http://.../orgaX> ) I1
query-local
dataset
{ ?p = <http://.../alice> }
Next?
Next?
tp2
= ( ?p , ex:interested_in , ?b ) I2
tp3
= ( ?b , rdf:type , <http://.../Book> ) I3
Pipeline of Link Traversing Iterators

30. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 30
Next?
Next?
tp3
= ( ?b , rdf:type , <http://.../Book> ) I3
tp1
= ( ?p , ex:affiliated_with , <http://.../orgaX> ) I1
tp2
= ( ?p , ex:interested_in , ?b )
tp2
' = ( <http://.../alice> , ex:interested_in , ?b )
I2
query-local
dataset
{ ?p = <http://.../alice> }
Pipeline of Link Traversing Iterators

31. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 31
Next?
Next?
tp3
= ( ?b , rdf:type , <http://.../Book> ) I3
tp1
= ( ?p , ex:affiliated_with , <http://.../orgaX> ) I1
tp2
= ( ?p , ex:interested_in , ?b )
tp2
' = ( <http://.../alice> , ex:interested_in , ?b )
I2
query-local
dataset
{ ?p = <http://.../alice> }
:
<http://.../alice> ex:interested_in <http://.../b1>
:
Pipeline of Link Traversing Iterators

32. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 32
Next?
Next?
tp3
= ( ?b , rdf:type , <http://.../Book> ) I3
tp1
= ( ?p , ex:affiliated_with , <http://.../orgaX> ) I1
tp2
= ( ?p , ex:interested_in , ?b )
tp2
' = ( <http://.../alice> , ex:interested_in , ?b )
I2
{ ?p = <http://.../alice> }
:
<http://.../alice> ex:interested_in <http://.../b1>
:
query-local
dataset
Pipeline of Link Traversing Iterators

33. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 33
Next?
tp3
= ( ?b , rdf:type , <http://.../Book> ) I3
tp1
= ( ?p , ex:affiliated_with , <http://.../orgaX> ) I1
tp2
= ( ?p , ex:interested_in , ?b )
tp2
' = ( <http://.../alice> , ex:interested_in , ?b )
I2
{ ?p = <http://.../alice> }
:
<http://.../alice> ex:interested_in <http://.../b1>
:
query-local
dataset
{ ?p = <http://.../alice> , ?b = <http://.../b1> }
Pipeline of Link Traversing Iterators

34. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 34
tp1
= ( ?p , ex:affiliated_with , <http://.../orgaX> ) I1
Next?
{ ?p = <http://.../alice> }
query-local
dataset
tp3
= ( ?b , rdf:type , <http://.../Book> ) I3
tp2
= ( ?p , ex:interested_in , ?b )
tp2
' = ( <http://.../alice> , ex:interested_in , ?b )
I2
{ ?p = <http://.../alice> , ?b = <http://.../b1> }
Pipeline of Link Traversing Iterators

35. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 35
tp1
= ( ?p , ex:affiliated_with , <http://.../orgaX> ) I1
Next?
{ ?p = <http://.../alice> }
query-local
dataset
tp3
= ( ?b , rdf:type , <http://.../Book> )
tp3
' = ( <http://.../b1> , rdf:type , <http://.../Book> )
I3
tp2
= ( ?p , ex:interested_in , ?b )
tp2
' = ( <http://.../alice> , ex:interested_in , ?b )
I2
{ ?p = <http://.../alice> , ?b = <http://.../b1> }
Pipeline of Link Traversing Iterators

36. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 36
tp1
= ( ?p , ex:affiliated_with , <http://.../orgaX> ) I1
Next?
{ ?p = <http://.../alice> }
tp3
= ( ?b , rdf:type , <http://.../Book> )
tp3
' = ( <http://.../b1> , rdf:type , <http://.../Book> )
I3
tp2
= ( ?p , ex:interested_in , ?b )
tp2
' = ( <http://.../alice> , ex:interested_in , ?b )
I2
{ ?p = <http://.../alice> , ?b = <http://.../b1> }
query-local
dataset
:
<http://.../Book> rdfs:subClassOf <http://.../CreativeWork>
:
Pipeline of Link Traversing Iterators

37. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 37
tp1
= ( ?p , ex:affiliated_with , <http://.../orgaX> ) I1
Next?
{ ?p = <http://.../alice> }
tp3
= ( ?b , rdf:type , <http://.../Book> )
tp3
' = ( <http://.../b1> , rdf:type , <http://.../Book> )
I3
tp2
= ( ?p , ex:interested_in , ?b )
tp2
' = ( <http://.../alice> , ex:interested_in , ?b )
I2
{ ?p = <http://.../alice> , ?b = <http://.../b1> }
query-local
dataset
:
<http://.../b1> rdf:type <http://.../Book>
:
Pipeline of Link Traversing Iterators

38. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 38
tp1
= ( ?p , ex:affiliated_with , <http://.../orgaX> ) I1
Next?
{ ?p = <http://.../alice> }
tp3
= ( ?b , rdf:type , <http://.../Book> )
tp3
' = ( <http://.../b1> , rdf:type , <http://.../Book> )
I3
tp2
= ( ?p , ex:interested_in , ?b )
tp2
' = ( <http://.../alice> , ex:interested_in , ?b )
I2
{ ?p = <http://.../alice> , ?b = <http://.../b1> }
:
<http://.../b1> rdf:type <http://.../Book>
:
query-local
dataset
Pipeline of Link Traversing Iterators

39. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 39
{ ?p = <http://.../alice> , ?b = <http://.../b1> }
tp1
= ( ?p , ex:affiliated_with , <http://.../orgaX> ) I1
{ ?p = <http://.../alice> }
tp3
= ( ?b , rdf:type , <http://.../Book> )
tp3
' = ( <http://.../b1> , rdf:type , <http://.../Book> )
I3
tp2
= ( ?p , ex:interested_in , ?b )
tp2
' = ( <http://.../alice> , ex:interested_in , ?b )
I2
{ ?p = <http://.../alice> , ?b = <http://.../b1> }
query-local
dataset
Pipeline of Link Traversing Iterators

40. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 40
tp1
= ( ?p , ex:affiliated_with , <http://.../orgaX> ) I1
tp3
= ( ?b , rdf:type , <http://.../Book> )
tp3
' = ( <http://.../b1> , rdf:type , <http://.../Book> )
I3
tp2
= ( ?p , ex:interested_in , ?b )
tp2
' = ( <http://.../alice> , ex:interested_in , ?b )
I2
Pipeline of Link Traversing Iterators
{ ?p = <http://.../alice> }
{ ?p = <http://.../alice> , ?b = <http://.../b1> }
Next?
query-local
dataset

41. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 41
tp1
= ( ?p , ex:affiliated_with , <http://.../orgaX> ) I1
tp3
= ( ?b , rdf:type , <http://.../Book> ) I3
tp2
= ( ?p , ex:interested_in , ?b )
tp2
' = ( <http://.../alice> , ex:interested_in , ?b )
I2
Pipeline of Link Traversing Iterators
{ ?p = <http://.../alice> }
Next?
Next?
query-local
dataset

42. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 42
tp1
= ( ?p , ex:affiliated_with , <http://.../orgaX> ) I1
tp3
= ( ?b , rdf:type , <http://.../Book> ) I3
tp2
= ( ?p , ex:interested_in , ?b )
tp2
' = ( <http://.../alice> , ex:interested_in , ?b )
I2
Pipeline of Link Traversing Iterators
{ ?p = <http://.../alice> }
Next?
Next?
query-local
dataset

43. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 43
● Deeply intertwines integrated execution + live exploration
● Data retrieval is a side-effect of calling link traversing iterators
● No need for a separate data retrieval operator
● Makes adding LTBQE to existing SPARQL engines easy
● Because those usually use iterators for execution
● Caveat: does not achieve the full flexibility
that is possible with LTBQE
● Iterators evaluate the triple patterns in a fixed order
● Iterators discard each input solution after using it
Pipeline of Link Traversing Iterators

44. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 44
?p ex:affiliated_with <http://.../orgaX>
?p ex:interested_in ?b
?b rdf:type <http://.../Book>
Query
Seed: <http://.../orgaX>
tp2
= ( ?p , ex:interested_in , ?b ) I2
tp3
= ( ?b , rdf:type , <http://.../Book> ) I3
tp1
= ( ?p , ex:affiliated_with , <http://.../orgaX>) I1
Alternative Execution Order

45. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 45
?p ex:affiliated_with <http://.../orgaX>
?p ex:interested_in ?b
?b rdf:type <http://.../Book>
Query
Seed: <http://.../orgaX>
tp2
= ( ?p , ex:interested_in , ?b ) I2
Alternative Execution Order
tp3
= ( ?p , ex:affiliated_with , <http://.../orgaX>) I3
tp1
= ( ?b , rdf:type , <http://.../Book> ) I1

46. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 46
?p ex:affiliated_with <http://.../orgaX>
?p ex:interested_in ?b
?b rdf:type <http://.../Book>
Query
Seed: <http://.../orgaX>
tp2
= ( ?p , ex:interested_in , ?b ) I2
query-local
dataset
Iterator Based Execution
tp1
= ( ?b , rdf:type , <http://.../Book> ) I1
tp3
= ( ?p , ex:affiliated_with , <http://.../orgaX>) I3

47. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 47
tp3
= ( ?p , ex:affiliated_with , <http://.../orgaX>) I3
tp2
= ( ?p , ex:interested_in , ?b ) I2
tp1
= ( ?b , rdf:type , <http://.../Book> ) I1
:
<http://.../alice> ex:affiliated_with <http://.../orgaX>
:
query-local
dataset
Alternative Execution Order

48. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 48
Next?:
<http://.../alice> ex:affiliated_with <http://.../orgaX>
:
query-local
dataset
Next?
tp1
= ( ?b , rdf:type , <http://.../Book> ) I1
Alternative Execution Order
Next?
tp2
= ( ?p , ex:interested_in , ?b ) I2
tp3
= ( ?p , ex:affiliated_with , <http://.../orgaX>) I3

49. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 49
Next?:
<http://.../alice> ex:affiliated_with <http://.../orgaX>
:
query-local
dataset
Next?
tp1
= ( ?b , rdf:type , <http://.../Book> ) I1
Alternative Execution Order
END!
tp2
= ( ?p , ex:interested_in , ?b ) I2
tp3
= ( ?p , ex:affiliated_with , <http://.../orgaX>) I3

50. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 50
query-local
dataset
tp1
= ( ?b , rdf:type , <http://.../Book> ) I1
tp2
= ( ?p , ex:interested_in , ?b ) I2
tp3
= ( ?p , ex:affiliated_with , <http://.../orgaX>) I3
END!
END!
END!
Computed query
result may depend
on the order of triple patterns
= logical query execution plan
Alternative Execution Order

51. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 51
Outline
 Separated Execution
 Integrated Execution
➢ General Idea and Properties
➢ Push-Based Implementation [LT10, LT11]
➢ Link Traversal Based Query Execution
√
√
√
√
Next part: 5. Query Planning and Optimization ...

52. WWW 2013 Tutorial on Linked Data Query Processing [ Execution Process ] 52
These slides have been created by
Olaf Hartig
for the
WWW 2013 tutorial on
Link Data Query Processing
Tutorial Website: http://db.uwaterloo.ca/LDQTut2013/
This work is licensed under a
Creative Commons Attribution-Share Alike 3.0 License
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