Handling time in RDF Claudio Gutierrez (Joint work with C. Hurtado - - PowerPoint PPT Presentation
Handling time in RDF Claudio Gutierrez (Joint work with C. Hurtado and A. Vaisman) Department of Computer Science Universidad de Chile UPM, Madrid, January 2009 Time in RDF p. 1/15 Outline Introducing time into RDF Temporal RDF
Claudio Gutierrez (Joint work with C. Hurtado and A. Vaisman)
Department of Computer Science Universidad de Chile
UPM, Madrid, January 2009
Time in RDF – p. 1/15
Time in RDF – p. 2/15
subC
subC
subC
type
subC
subC
subC
subC
type
subC
subC
subC
subC
type
[0,Now]
[0,Now]
[3,Now]
[0,Now]
[0,3]
– Label elements subject to change – Maintain a snapshot of each state of the graph
Time in RDF – p. 5/15
– Label elements subject to change – Maintain a snapshot of each state of the graph
[4, 31] = [4] ∪ [5] ∪ · · · ∪ [30] ∪ [31]
Time in RDF – p. 5/15
– Label elements subject to change – Maintain a snapshot of each state of the graph
[4, 31] = [4] ∪ [5] ∪ · · · ∪ [30] ∪ [31]
– Point based (variables refer to point times) – Interval based (variables refer to intervals)
Time in RDF – p. 5/15
=τ
[2,7] sc
[5,7]
[5,9] sc
Time in RDF – p. 6/15
=τ
[2,7] sc
[5,7]
[5,9] sc
[2,3]
[3,5]
| =τ
X
[2,5]
=τ
[2,7] sc
[5,7]
[5,9] sc
[2,3]
[3,5]
| =τ
X
[2,5]
Time in RDF – p. 6/15
Temporal Triple: an RDF triple with a temporal label, e.g. (a, b, c)[t] Temporal Graph: set of temporal triples Snapshot of graph G at time t:
G(t) = {(a, b, c) : (a, b, c)[t] ∈ G}
Notion of temporal entailment G1 |
=τ G2
Time in RDF – p. 7/15
Ground Case:
G1 | =τ G2 if for each t, G1(t) | = G2(t)
Time in RDF – p. 8/15
Ground Case:
G1 | =τ G2 if for each t, G1(t) | = G2(t)
Non Ground Case:
G1 | =τ G2 if there are ground instances µ1(G1) and µ2(G2) such that for each t: µ1(G1)(t) | =τ µ2(G2)(t)
Time in RDF – p. 8/15
Ground Case:
G1 | =τ G2 if for each t, G1(t) | = G2(t)
Non Ground Case:
G1 | =τ G2 if there are ground instances µ1(G1) and µ2(G2) such that for each t: µ1(G1)(t) | =τ µ2(G2)(t)
=τ G2 implies G1(t) | = G2(t) for all times t.
Time in RDF – p. 8/15
The temporal closure tcl(G) is a maximal set of temporal triples G′ such that: – G′ contains G – G is equivalent to G′ Proposition.
G1 | =τ G2 iff tcl(G1) | =τ G2
DP-complete.
Time in RDF – p. 9/15
a
Instant
4 c X
tsubj
Instant
5 c
Time in RDF – p. 10/15
a
Instant
4 c X
tsubj
Instant
5 c
a
c X
tsubj
Y
Interval
Z
initial
5
Time in RDF – p. 10/15
Rule 1-2: Equivalence betwen point and interval versions Rule 3: Normalization of point-version:
a
Instant
4 c X
tsubj
Z
Instant
5 c
Time in RDF – p. 11/15
Rule 1-2: Equivalence betwen point and interval versions Rule 3: Normalization of point-version:
a
c X
tsubj
V
Instant
c
Time in RDF – p. 11/15
(a, b, c)[m, n] . ( )∗
( )∗
c X
Y
Int
Z
init
n
Time in RDF – p. 12/15
Theorem.
=τ G2 implies (G1)∗ | = (G2)∗
= G2 implies (G1)∗ | =τ (G2)∗
= (G∗)∗
rules plus Temporal rules. Then:
G1 | =τ G2 iff (G1)∗ ⊢ (G2)∗
Time in RDF – p. 13/15
Proposal: Conjunctive fragment with – interval and point variables – aggregate functions – constructor of graphs for answers
Time in RDF – p. 14/15
Proposal: Conjunctive fragment with – interval and point variables – aggregate functions – constructor of graphs for answers
2000
when this occurred
Ph.D program in no more than 4 years
Time in RDF – p. 14/15
complexity of RDF
Time in RDF – p. 15/15