An introduction to the Linked Data concepts, tools and architectures to build data APIs.

1. Linked Data APIs
May 2015

2. Linked Open Data in 1 slide
1. URIs
2. Uniform access
3. Uniform representation
4. Links

3. Web of linked documents
1. URLs
2. HTTP GET/POST
3. HTML (DOM tree)
4. href

4. Web of linked data
1. Use URIs to name things
2. Make URIs accessible through HTTP with
standard uniform semantics (REST)
3. Use standard uniform representations for the
exposed things (RDF)
4. Link representations

5. A note on RDF
Uniform and general data model
Carlos
33 31
Jillhttp://mexicans.mx/Carlos#me
http://britons.co.uk/Jill#me
foaf:friendOf
foaf:age
foaf:age
foaf:name
foaf:name

6. A note on RDF
Abstract graph, concrete triples
http://mexicans.mx/Carlos#me foaf:age (33 xsd:int)
http://mexicans.mx/Carlos#me foaf:name (‘Carlos’ xsd:string)
http://mexicans.mx/Carlos#me foaf:friendOf http://britons.co.uk/Jill#me
http://britons.co.uk/Jill#me foaf:age (31 xsd:int)
http://britons.co.uk/Jill#me foaf:name (‘Jill’ xsd:String)
http://britons.co.uk/Jill#me foaf:friendOf http://mexicans.mx/Carlos#me

7. A note on RDF
GET http://mexicans.mx/Carlos#me
Accept: application/json+ld
GET http://mexicans.mx/Carlos
Accept: application/json+ld
{
"@id": "http://mexicans.mx/Carlos#me",
"name": "Carlos",
"age": 33,
"knows": "http://britons.co.uk/Jill#me",
"@context": {
"@vocab": "http://xmlns.com/foaf/0.1/",
"friendOf": {"@type":"@id"}
}
}
http://mexicans.mx/Carlos#me foaf:age (33 xsd:int)
http://mexicans.mx/Carlos#me foaf:name (‘Carlos’ xsd:string)
http://mexicans.mx/Carlos#me foaf:friendOf http://britons.co.uk/Jill#me
Carlos
33
http://mexicans.mx/Carlos#me
foaf:friendOf
foaf:age
foaf:name
http://britons.co.uk/Jill#me

8. A note on RDF
GET http://britons.co.uk/Jill#me
Accept: text/n3
GET http://britons.co.uk/Jill
Accept: text/n3
<http://britons.co.uk/Jill#me>
<foaf:name> “Jill” ;
<foaf:age> 35^^<xsd:int> ;
<foaf:friendOf> <http://mexicans.mx/Carlos#me> .
http://britons.co.uk/Jill#me foaf:age (31 xsd:int)
http://britons.co.uk/Jill#me foaf:name (‘Jill’ xsd:String)
http://britons.co.uk/Jill#me foaf:friendOf http://mexicans.mx/Carlos#me
Carlo
s
33 31
http://mexicans.mx/Carlos#me
http://britons.co.uk/Jill#me
foaf:friendOf
foaf:age
foaf:age
foaf:name
foaf:name
Jill

9. LD API architecture
ABox / Data (RDF)
TBox / Schema
(OWL,FOAF,FIBO)
Relatio
nal DB
Triple
Store
Physical Mapping (R2RML)
Conceptual RDF graph
Linked
Resource
Graph partition
HTTPS
CRUD Semantics / SPARQL
REST Semantics / Linked
Data Platform (LDP)
Representa
tion
JSON-LD, N3, Turtle, RDF/XML
URL
Legacy
API
Authentication / WebID
(W3C Recommendations)

10. API design advice
● Use URIs, not db ids, UUIDs...
● Design a data model, not end-points
● Re-use vocabularies / ontologies
● Link entities, don’t embed them
● Data needs a schema / meta-data
● Representation is different from data model

11. Demo
https://github.com/antoniogarrote/geektalk

12. Github
JSON-LD Macro
RDFStore-js
Stack OverflowTwitter
JSON-LD
DOM Nodes
RDF Graph / DOM Tree declarative bindings (SemKO+SPARQL)