What are Linked Data?
by @_pieroit_
"why should I care about a globally distributed hypertext when the whole encyclopedia sits in a CD?"
"... WikiPedia"
2006 proposal for a M2M web
1. Use URIs as names for things
2. Use HTTP URIs so that people can look up those names
3. When someone looks up a URI, provide useful information, using the standards (RDF*, SPARQL)
4. Include links to other URIs so that they can discover more things
Resource Description Framework
RDF : Linked Data = HTML : Hypertext
S P O
Resource Description Framework
RDF : Linked Data = HTML : Hypertext
# subject # predicate # object
<http://example.com/grandma> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://schema.org/Person> .
<http://example.com/grandma> <http://schema.org/relatedTo> <http://example.com/me> .
<http://example.com/grandma> <https://schema.org/birthDate> "1934" .
<http://cookingsite.net/pie> <http://schema.org/author> <http://example.com/grandma> .
<http://cookingsite.net/pie> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://schema.org/Recipe> .
<http://cookingsite.net/pie> <http://schema.org/recipeIngredient> <http://foodnoprofit.info/apple> .
<http://example.com/me> <http://schema.org/owns> <http://foodnoprofit.info/apple> .
<http://example.com/me> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://schema.org/Person> .
S P O
"why should I care about a globally distributed database when all my data can sit in my server/cluster?"
"... Wikidata"
(and the Linked Data Cloud)
Open standard
no royalties!
Decentralization
anybody can publish and link data
... even computer grandma!
Interoperability
public agreement on a data format
cross-domain queries!
Self descriptive
data and metadata
are expressed in the same way
No data silos
data and application
are two different things
Solid project
(on nodejs)
Onthologies
agreement on objects and relations
Amazing open data!
Queries
"Give me world recipes containing Black Pepper and Eggs"
PREFIX dbo: <http://dbpedia.org/ontology/>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
SELECT DISTINCT ?s, ?l WHERE {
?s a dbo:Food .
?s dbo:ingredient <http://dbpedia.org/resource/Black_pepper> .
?s dbo:ingredient <http://dbpedia.org/resource/Egg_(food)> .
?s rdfs:label ?l .
FILTER (lang(?l) = "en")
}
Queries
"Give me movies based on books written by science fiction writers"
PREFIX wd: <http://www.wikidata.org/entity/>
PREFIX wdt: <http://www.wikidata.org/prop/direct/>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
SELECT ?p ?w ?m WHERE {
?m wdt:P31 wd:Q11424 . # ?m is a Movie
?m wdt:P144 ?w . # ?m is based on ?w
?w wdt:P50 ?p . # ?w written by ?p
?p wdt:P106 wd:Q18844224 . # ?p is a science fiction writer
}
PREFIX wd: <http://www.wikidata.org/entity/>
PREFIX wdt: <http://www.wikidata.org/prop/direct/>
SELECT
?x ?xLabel ?nationalityLabel ?haircolorLabel ?img
WHERE {
?x wdt:P106 wd:Q488111 .
?x wdt:P27 ?nationality .
?x wdt:P1884 ?haircolor .
?x wdt:P18 ?img .
FILTER( ?nationality IN (wd:Q159, wd:Q28) )
SERVICE wikibase:label { bd:serviceParam wikibase:language "en" }
}
Queries
"Voti alla Camera del 19/10/2017: Disposizioni concernenti la coltivazione e la somministrazione della cannabis a uso medico."
SELECT DISTINCT
?votazione ?descrizione ?numeroVotazione
?nome ?cognome ?espressione ?infoAssenza ?deputato
WHERE {
## Votazioni del 19 Ottobre 2017
?votazione a ocd:votazione;
dc:date '20171019';
dc:description ?descrizione;
dc:identifier ?numeroVotazione.
## voti espressi
?voto a ocd:voto;
ocd:rif_votazione ?votazione;
dc:type ?espressione;
ocd:rif_deputato ?deputato.
OPTIONAL{?voto dc:description ?infoAssenza}
## info deputato
?deputato foaf:surname ?cognome;
foaf:firstName ?nome.
}
ORDER BY ?cognome
So, how do we query the web?
So, how do we query the web?
Problems
-
ivory towers
-
immature stack
-
no killer app (SEO?)
-
what about REST APIs?
SEO
JSON-LD
official W3C recommendation
{
"@context" : "http://schema.org/",
"@type" : "Person",
"name" : "Fraccarso da Velletri",
"jobTitle" : "Professor",
"telephone": "(425) 123-4567",
"url" : "http://frac-da-velletri.org",
"knows" : "http://..........",
"sameAs" : "http://wikidata/entity/..."
}
RDF-JS
W3C community group
Thanks
What are Linked Data?
By Piero Savastano
What are Linked Data?
Linked data is the future of the web.
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