Discovering Knowledge in Linked Data

James Earl Douglas

April 24, 2015

The approach

Explore individual facts

Synthesize the bigger picture

Richard Feynman was born in Queens, which is a borough of New York City in the United States.

How to get there

Build on foundations of the Semantic Web.

Semantic Wuzzah?

Semantic Web

It's the Web we all know, but with a bit of structure around the information.

Where is it?

Lots of places!

What's structure?

Consider an HTML list.

Rather than a flat string, "electrons, protons, and neutrons", it has structure:

<ul>
  <li>Electrons</li>
  <li>Protons</li>
  <li>Neutrons</li>
</ul>

Moar structure: triples

Richard Feynman plays the bongo drum.

Resource Description Framework

An ecosystem of standards for specifying, among other things, triples.

Trouble with Triples

Triples are great at capturing facts, but seem overwhelmingly complex.

Too many standards

RDF, RDFS, N-Triples, Turtle, SPARQL, etc.

https://xkcd.com/927/

Unreadability of RDF

What does this say?

<http://www.wikidata.org/entity/Q39246>
  <http://www.wikidata.org/entity/P108s>
  <http://www.wikidata.org/entity/Q39246SE1E55ECD-9A13-49BC-B6FD-99995E4C0FC7> .
<http://www.wikidata.org/entity/Q39246SE1E55ECD-9A13-49BC-B6FD-99995E4C0FC7>
  <http://www.wikidata.org/entity/P108v>
  <http://www.wikidata.org/entity/Q49115> .
<http://www.wikidata.org/entity/Q49115>
  <http://www.wikidata.org/entity/P373s>
  <http://www.wikidata.org/entity/Q49115SEE3BD997-DA49-4A40-8648-2118D414D82D> .
<http://www.wikidata.org/entity/Q49115SEE3BD997-DA49-4A40-8648-2118D414D82D>
  <http://www.wikidata.org/entity/P373v>
  "Cornell University" .
"Richard Feynman works for Cornell University."

Turtle makes it better

De-duplicate some of the redundancy.

@prefix entity: <http://www.wikidata.org/entity/> .

entity:Q39246
  entity:P108s
  entity:Q39246SE1E55ECD-9A13-49BC-B6FD-99995E4C0FC7 .
entity:Q39246SE1E55ECD-9A13-49BC-B6FD-99995E4C0FC7
  entity:P108v
  entity:Q49115 .
entity:Q49115
  entity:P373s
  entity:Q49115SEE3BD997-DA49-4A40-8648-2118D414D82D .
entity:Q49115SEE3BD997-DA49-4A40-8648-2118D414D82D
  entity:P373v
  "Cornell University" .

SPARQL does too

PREFIX entity: <http://www.wikidata.org/entity/>

SELECT ?employer WHERE {
  entity:Q39246 entity:P108s ?a .
  ?a entity:P108v ?b .
  ?b entity:P373s ?c .
  ?c entity:P373v ?employer .
}

Moreso with property paths

PREFIX entity: <http://www.wikidata.org/entity/>

SELECT ?employer WHERE {
  entity:Q39246
    entity:P108s/entity:P108v/entity:P373s/entity:P373v
    ?employer .
}

Domain-specific language

Let's extend SPARQL just a little bit, to make things even simpler.

So fresh, so clean

SELECT ?employer WHERE {
  [Q:feynman] [P:employedBy]/[P:labelled] ?employer .
}

What can we do with it?

Ask simple questions, such as "What happened on this day in history?".

SELECT ?entity ?date WHERE {
  ?entityS ?x           ?dateS        .
  ?dateS   ?y           ?dateV        .
  ?dateV   [O:calendar] [Q:gregorian] .
  ?dateV   [O:time]     ?date         .
  ?entityS [P:labelled] ?entity       .
  FILTER ( regex(str(?date), "\\d{4}-\\d{2}-\\d{2}") )
  FILTER ( [X:int](substr(str(?date), 6, 2)) = month(now()) )
  FILTER ( [X:int](substr(str(?date), 9, 2)) = day(now()) )
}

What happened on this day in history?

entity date
Mexican-American War 1846-04-24
Girolamo Crescentini 1846-04-24
Philatelic fakes and forgeries 1846-04-24
David Oliver 1982-04-24
Kelly Clarkson 1982-04-24
John M. Ashbrook 1982-04-24

What else can we do with it?

Ask tricky questions, such as "What were some of the fields of work of physicists who worked at institutions where Richard Feynman also worked?".

SELECT ?colleague ?field ?employer WHERE {
  [Q:feynman]  [P:employedBy]   ?employerS    .
  ?colleagueS  [P:employedBy]   ?employerS    .
  ?colleagueS  [P:occupiedAs]   [Q:physicist] .
  ?employerS   [P:labelled]     ?employer     .
  ?colleagueS  [P:labelled]     ?colleague    .
  ?colleagueS  [P:worksInField] ?fieldS       .
  ?fieldS      [P:labelled]     ?field        .
}

What is the answer to that wicked long question?

colleague field employer
Richard Feynman Particle physics Cornell University
Richard Feynman Particle physics California Institute of Technology
J. Robert Oppenheimer Theoretical physics California Institute of Technology
J. Robert Oppenheimer Nuclear physics California Institute of Technology

Explore statements, acquire knowledge

The Semantic Web may seem daunting at first, but it's worth the trouble.

Following connections wrapped up in related statements, we can build an enormous map of increasingly complex understanding.

Get involved

References and further reading