MOMENT: Temporal Meta-Fact Generation and Propagation in Knowledge Graphs [F. Saïs, J. E. Gonzales Malaverri and G. Quercini @ACM-SAC-SWA 2020] This paper deals with the problem of temporal meta-fact genera- tion in RDF knowledge graphs (KGs). These temporal meta-facts represent the time validity of facts, for instance, <Barack Obama, presidentOf, United States of America> is valid for the period [2008..2016]. We propose an approach called MOMENT that com- bines two methods, the first uses a set of specified rules to generate meta-facts in knowledge bases where no temporal meta-fact exist. The second method exploits existing temporal meta-facts and a set of Horn rules generated by AMIE [9] to propagate the meta-facts and thus expand the set of temporal meta-facts. An experimental evaluation has been conducted using Yago, DBpedia and Wikidata datasets. The obtained results are promising and showed the relevance of such an approach for temporal meta-fact generation in Knowledge Graphs.

1. MOMENT –TEMPORAL META-FACT
GENERATION AND PROPAGATION IN
KNOWLEDGE GRAPHS
FATIHA SAÏS, JOANA E. GONZALES MALAVERRI,
AND GIANLUCA QUERCINI
LRI, CNRS & Paris Saclay University, France
ACM SAC-SWA, March 31h, 2020
1

2. KNOWLEDGE GRAPHS (KGS)
"Linking Open Data cloud diagram 2017, by Andrejs Abele, John
P. McCrae, Paul Buitelaar, Anja Jentzsch and Richard Cyganiak.
http://lod-cloud.net/" 2

3. facts
KNOWLEDGE GRAPHS (KGS)
"Linking Open Data cloud diagram 2017, by Andrejs Abele, John
P. McCrae, Paul Buitelaar, Anja Jentzsch and Richard Cyganiak.
http://lod-cloud.net/" 3
.
.
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4. KNOWLEDGE GRAPHS (KGS)
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5. 5
2012
2013
2015 2016
2013
2007
2007
2007
2012
Academic side Commercial side
WHO IS DEVELOPING
KNOWLEDGE GRAPHS?

6. § KG Creation
§ Information extraction from web pages (DBpedia, Yago),
collaborative (Wikidata), ...
§ KG Enrichment and Expansion
§ Content prediction, data fusion, data/knowledge linking, ...
§ KG Validity
§ Dealing with errors and ambiguities
§ Fact validity
§ Timeliness: truth of statements often changes with time:
§ E.g., Currently, who is the US president?
KNOWLEDGE GRAPHS: SOME
KEY PROBLEMS
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7. KGS – WHY TIME MATTERS?
l Time period during which a fact is valid: validity time.
- f1: <#Obama presidentOf US> is true in the temporal context [2008-2016]
- f2: <#Trump presidentOf US> is true in the temporal context [2016-now]
l Query answering
l Consistency checking
l Sort the sequence of facts.
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8. PROBLEM AND PROPOSED APPROACH
Problem
§ How can we capture fact validity time using only
the facts and the structure of the KGs?
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9. PROBLEM AND PROPOSED APPROACH
Problem
§ How can we capture fact validity time using only
the facts and the structure of the KGs?
Approach – Seed meta-fact generation (step 1)
9Knowledge Patterns

10. PROBLEM AND PROPOSED APPROACH
Problem
§ How can we capture fact validity time using only
the facts and the structure of the KGs?
Approach – Seed meta-fact generation (step 1)
10Knowledge Patterns

11. PROBLEM AND PROPOSED APPROACH
Temporal meta-fact
Problem
§ How can we capture fact validity time using only
the facts and the structure of the KGs?
Approach – Seed meta-fact generation (step 1)
11Knowledge Patterns

12. 1. SEED META-FACT GENERATION
l Focus on predicates that may change over time:
- Brad Pitt acted in:
l the Fight Club in 1999
l the Curious Case of Benjamin Button in 2008
- Paul McCartney was/is married with:
l Heather Mills from 2002 to 2008
l Nancy Shevell since 2011
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13. 1. SEED META-FACT GENERATION
Algorithm: Query generation
§ For each knowledge pattern, in the form of:
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14. 1. SEED META-FACT GENERATION
Algorithm: Query generation
§ For each knowledge pattern, in the form of:
§ Generate a SPARQL query (graph pattern = rule premise)
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15. 1. SEED META-FACT GENERATION
Algorithm: Meta-fact generation
§ On the set of facts obtained from SPARQL queries, generate the
set of temporal meta-facts
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16. 1. SEED META-FACT GENERATION
Algorithm: Meta-fact generation
§ On the set of facts obtained from SPARQL queries, generate the
set of temporal meta-facts
§ For interval knowledge patterns: compute an intersection
between the temporal intervals associated to the subject and the
object of a fact.
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17. 1. SEED META-FACT GENERATION
Algorithm: Meta-fact generation
§ On the set of facts obtained from SPARQL queries, generate the
set of temporal meta-facts
§ For interval knowledge patterns: compute an intersection
between the temporal intervals associated to the subject and the
object of a fact.
Start-date
End-date 17

18. TEMPORAL META-FACT
EXPANSION
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19. 2. TEMPORAL META-FACT EXPANSION
§ Use a set of Horn rules (generated by AMIE) to propagate existing
temporal meta-facts
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20. 2. TEMPORAL META-FACT EXPANSION
§ Use a set of Horn rules (generated by AMIE) to propagate existing
temporal meta-facts
§ Step 1: Rule selection and instantiation
§ Keep only rule with PCA-confidence > theta
§ Select those premises contain a predicate in the set of seed
meta-facts
§ Rule instantiation on a set of facts and seed meta-facts
(generated or already existing in the KG)
20

21. 2. TEMPORAL META-FACT EXPANSION
§ Use a set of Horn rules (generated by AMIE) to propagate existing
temporal meta-facts
§ Step 2: Temporal meta-fact propagation
§ Case 1: only one meta-fact in the premise, then propagate the
date attached to the conclusion
§ Case 2: if several meta-facts in the premise, then apply
temporal combination constraints
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22. 2. TEMPORAL COMBINATION
CONSTRAINTS
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23. 2. TEMPORAL COMBINATION
CONSTRAINTS
§ Use of Allen’s interval relationships: during(TI, TI’), overlaps(TI, TI’),
meets(TI, TI’), …
§ Apply one of the twelve combination constraints we defined, such as:
TI1 TI2
S(TI1) E(TI1)S(TI2) E(TI2)
TI3
S(TI3) E(TI3)
è
Inferred time interval
23

24. 2. META-FACT CONFIDENCE
Assign for each inferred meta-fact a confidence value in [0;1], using:
§ Quality scores of the used rule: Head-Coverage, PCA-confidence
§ K1: #meta-facts associated with the atoms of the rule premise
§ K2: the sum of the distances between the temporal meta-facts of
the premise
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25. EXPERIMENTS
25

26. § Yago: contains information extracted from
Wikipedia infoboxes, WordNet, and GeoNames,
§ > 10 million entities (persons, cities,
organizations),
§ > 120 million facts about these entities
§ Attaches temporal and spatial dimensions to
some facts and entities.
1. SEED META-FACT GENERATION:
EXPERIMENTS ON YAGO
Time-sensitive predicates
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27. 1. SEED META-FACT GENERATION:
EXPERIMENTS ON YAGO
Quantitative results of seed meta-fact generation
27
x 8479
x 228
x 100
x 6
x 67

28. 1. SEED META-FACT GENERATION:
EXPERIMENTS ON YAGO
Qualitative evaluation on Movie case study
- Use of IMDb as a ground truth
- Comparaison with yago meta-facts IMDb - page
28

29. l Movie domain data in YAGO:
- # of films: 151427
- # of actors: 47800
- # of release dates available: 136234
1. SEED META-FACT GENERATION:
EXPERIMENTS ON YAGO
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30. 1. SEED META-FACT GENERATION:
EXPERIMENTS ON YAGO
l Evaluation of 5200 meta-facts of actedin predidcate
l Movie-title and actor-name equal IMDb title and one of the
IMDb actors’ name
l 25% of release date in Yago are different with IMDb release
date: premiere date in IMDb and shown in a festival date in
yago
30

31. 1. SEED META-FACT GENERATION:
EXPERIMENTS ON YAGO
l Evaluation of 5200 meta-facts of actedin predidcate
l Movie-title and actor-name equal IMDb title and one of the
IMDb actors’ name
l 25% of release date in Yago are different with IMDb release
date: premiere date in IMDb and shown in a festival date in
yago
l Results:
l Reach of 75% of precision for timestamp meta-facts.
l Some meta-facts are not inferred, some films have no release
date in Yago.
l Some obtained interval meta-facts are too large: need to be
refined
31

32. 2. TEMPORAL META-FACT
EXPANSION: EXPERIMENTS
§ Dbpedia as a KG to be enriched with temporal meta-facts
§ As seed meta-facts:
§ Yago meta-facts: datasets A
§ Seed meta-facts: dataset B
§ Use of AMIE horn rules
§ Wikidata as a ground truth (qualifiers)
§ Use of Wikidata endpoint *
* https://query.wikidata.org/ 32

33. 2. TEMPORAL META-FACT
EXPANSION: EXPERIMENTS
§ Quantitive results on dataset A (Yago meta-facts)
33

34. 2. TEMPORAL META-FACT
EXPANSION: EXPERIMENTS
§ Quantitive results on dataset B (Seed meta-facts, step1)
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35. 2. TEMPORAL META-FACT
EXPANSION: EXPERIMENTS
Qualitative results: Considered timestamp meta-facts and full date
§ Dataset A gets better results: better accuracy of seed meta-facts
§ Dataset B reaches 0.67 of F-measure
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36. CONCLUSION
l An approach for seed temporal meta-fact
generation for time-sensitive predicates
l A rule-based approach for temporal meta-fact
propagation
l A first quantitative and qualitative evaluation
36

37. FUTURE WORK
§ Develop an approach to learn time-sensitive (evolving)
predicates.
§ Improvements are needed for seed interval meta-facts
generation
§ Fact validity assessment using temporal-meta facts
§ Combine temporal and spatial reasoning:
§ E.g.: Film release dates are associated to specific
locations (country, city).
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38. ACKNOWLEDGMENTS
l Labex DigiCosme (Paris Sacaly): VASTE
Project
l CNRS: RegleX PEPS Project
38

39. MOMENT –TEMPORAL META-FACT
GENERATION AND PROPAGATION IN
KNOWLEDGE GRAPHS
FATIHA SAÏS, JOANA E. GONZALES MALAVERRI,
AND GIANLUCA QUERCINI
LRI, CNRS & Paris Saclay University, France
ACM SAC-SWA, March 31h, 2020
39
Thanks