Knowledge Graphs are an information system design pattern that is gaining a lot of attention. Originally developed by Google and other large companies, the techniques are now spreading out to mere mortals. In this talk we will discuss what is a knowledge graph (and what it isn't), then look at technology for building a knowledge graph using W3C standards.

1. Knowledge Graphs
Andy Seaborne
South West Data : 24th April 2019

2. Outline
● Knowledge Graphs
● Graphs for data
● Standards-based Graph Databases

3. Knowledge Graphs
● Original: Google "knowledge panel"
○ Search augmentation
● Google Assistant
● Facebook Social Graph
○ https://developers.facebook.com/docs/graph-api/
● eBay products
● Emerging internal Enterprise uses

4. Google

5. What is a Knowledge Graph?
https://2019.semantics.cc/knowledge-graphs-are-rise
● A Knowledge Graph represents a knowledge domain
● It represents knowledge as a graph
● a network of nodes and links
● not tables of rows and columns
● It represents facts (data) and models (metadata) in the same way

6. WHAT IS A KNOWLEDGE GRAPH?
“A knowledge graph acquires and integrates information into an
ontology and applies a reasoner to derive new knowledge.”
Towards a Definition of Knowledge Graphs
SEMANTICS 2016: Posters and Demos Track

7. WHAT IS A KNOWLEDGE GRAPH?
“A knowledge graph acquires and integrates information into an
ontology and applies a reasoner to derive new knowledge.”
Towards a Definition of Knowledge Graphs
SEMANTICS 2016: Posters and Demos Track

8. Reality
Data
“Integrates” => can be many sources;data come from other places
“Ontology” => organised
“Reasoner”, “machine learning” => programs that make the graph more useful

9. Another take . . .
https://medium.com/@dmccreary/knowledge-graphs-the-third-era-of-computing-a8106f343450

10. https://github.com/eBay/beam

12. Knowledge Graph
● An approach, not a specific technology
● Integrates
○ Many sources
○ Variety of sources
● Refines the data
○ Puts some level of organisation on the data
○ Makes connections across sources
● Answer questions
○ Supplies an API or a UI for delivery of organised data
○ “Publishes data” : not a single planned, fixed usage.

13. Now:
● General term for a graph of data produced from many sources.
● Background knowledge for AI and ML

14. Public Examples
DBPedia
Wikidata
Uniprot

15. Gartner 2018

16. Graph Databases
… for Knowledge Graphs

17. While the term “Knowledge Graph” is relatively new
(Google 2012), the concept of “representing knowledge
as a set of relations between entities — forming a
“graph” — has been around for much longer.
https://dzone.com/articles/my-list-of-7-great-2018-advancements-in-enterprise

18. Graphs for Data
http://www.linkeddatatools.com/introducing-rdf

19. Why Graph Databases
● “Schemaless” and Publishing
● Data not completely regular … or clean … or cleanable
● “Connections”
● Traversal

20. Two kinds
RDF
● W3C Standards
● From 1999
● Focus:
○ Data Publishing
○ Data Integration
○ Web scale
○ Modelling
○ Rules
● Query language: SPARQL
Property Graphs
● A general style, currently
converging
● Focus:
○ Data capture
○ Analytics
○ Large datasets
○ Data structure
● Query languages: Gremlin,
OpenCypher

21. Why RDF graph databases
Emphasis
● Modelling
● Concept naming
● Merge

22. RDF Graph Database

25. https://www.topquadrant.com/technology/graphql/

26. RDF Data
PREFIX : <http://example/myData/>
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX foaf: <http://xmlns.com/foaf/0.1/> # "foaf" = Friend of a Friend
# foaf:name is a short form of <http://xmlns.com/foaf/0.1/name>
:alice rdf:type foaf:Person ;
foaf:name "Alice Smith" ;
foaf:knows :bob .
:alice
foaf:knows
"Alice Smith"
foaf:name
:bob
foaf:Person
rdf:type

27. RDF Data
PREFIX : <http://example/myData/>
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
:bob
rdf:type foaf:Person ;
foaf:name "Bob Brown" .
:bob
foaf:Person
rdf:type
foaf:name
"Bob Brown"

28. RDF Data
PREFIX : <http://example/myData/>
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX foaf: <http://xmlns.com/foaf/0.1/> # “foaf” = Friend of a Friend
:alice rdf:type foaf:Person ;
foaf:name "Alice Smith" ;
foaf:knows :bob .
:bob
rdf:type foaf:Person ;
foaf:name "Bob Brown" . :alice
foaf:knows
"Alice Smith"
foaf:name
:bob
foaf:Person
rdf:type rdf:type
:bob
foaf:name
"Bob Brown"

29. FOAF : Friend of a Friend
http://xmlns.com/foaf/spec/
● Dan Brickley, Libby Miller
Bristol !

30. foaf:Person
http://xmlns.com/foaf/spec/#term_Person

31. foaf:Person - for machines
{
"@id": "foaf:Person",
"@type": [
"rdfs:Class",
"owl:Class"
],
"comment": "A person.",
"label": "Person",
"subClassOf": [
"foaf:Agent",
"http://www.w3.org/2000/10/swap/pim/contact#Person",
"http://www.w3.org/2003/01/geo/wgs84_pos#SpatialThing"
],
"disjointWith": [
"foaf:Organization",
"foaf:Project"
],
"status": "stable"
}
JSON-LD, another RDF syntax. Used with scheme.org.

32. Class Hierarchies
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
foaf:Person rdfs:subClassOf foaf:Agent .
foaf:Person rdfs:subClassOf
<http://www.w3.org/2003/01/geo/wgs84_pos#SpatialThing> .
foaf:skypeID
rdfs:domain foaf:Agent ;
rdfs:label "Skype ID" ;
rdfs:range rdfs:Literal .
Class Hierarchy itself is in RDF syntax.

33. SPARQL
Query Language for RDF
W3C Recommendation
Currently SPARQL 1.1

35. TheGuardian using DBPedia
https://www.theguardian.com/info/2019/mar/08/has-mary-wollstonecrafts-cpu-spiked

36. Summary
Knowledge Graphs for data integration
Graph databases to contain variable shape data
RDF databases for standard-based data exchange, modelling and query.
Open source systems to build Knowledge Graphs.