Consuming RDF: Nuts and Bolts

Materials for a hands-on session at the Web of Data Practicioners Day.

Update, 9 Nov 2008: Johannes Hercher of FH Postsdam has created a mindmap of the material presented in the session, which includes live links for many of the queries and examples. Thanks, Johannes!

Links and Tools

RDF/XML Validator

Can show triples and draw a graph

N3 Validator

Seems to be down today :-(

triplr.org - fast converter between different data formats

RDF/XML, N3, N-Triples, RSS, GRDDL, JSON, ...; input must be on the Web, output will be a new URI

Babel - converter between different data formats

Has Exhibit preview; can mix several input files

Tabluator Firefox Extension

The first Linked Data browser

Marbles Linked Data Browser

Shows provenance in mixed descriptions

Exhibit faceted browser

Displays Exhibit data files (JSON); easy to embed in your own sites/pages

Sindice search engine

Finds RDF and microformat documents. Has an API.

cURL - HTTP command line tool

Useful for looking up and debugging URIs

Exploring the WOD-PD Dataset

Yves Raimon

http://api.talis.com/stores/wod-pd-sandbox/items/People/YvesRaimond

Snorql - a SPARQL explorer

http://dowhatimean.net/wod-pd/

SPARQL Endpoint

http://api.talis.com/stores/wod-pd-sandbox/services/sparql

Yves and all his attributes - Run this in Snorql

SELECT ?property ?value
WHERE {
  people:YvesRaimond ?property ?value
}

Exploring classes

SELECT DISTINCT ?class
WHERE { ?x a ?class }

Exploring properties

SELECT DISTINCT ?property
WHERE { ?s ?property ?o }

List all people

SELECT *
WHERE {
  ?person a foaf:Person
}

List only the people added yesterday

SELECT *
WHERE {
  ?person a foaf:Person
  FILTER (REGEX(STR(?person), "^http://api.talis.com/stores/wod-pd-sandbox/items/People/"))
}

Which properties are used to describe people?

SELECT DISTINCT ?property
WHERE {
  ?person a foaf:Person .
  ?person ?property ?value .
  FILTER (REGEX(STR(?person), "^http://api.talis.com/stores/wod-pd-sandbox/items/People/"))
}
ORDER BY ?property

Show people with one of the properties

SELECT DISTINCT ?person ?value
WHERE {
  ?person a foaf:Person .
  ?person foaf:nick ?value .
  FILTER (REGEX(STR(?person), "^http://api.talis.com/stores/wod-pd-sandbox/items/People/"))
}

List people with additional attributes

SELECT *
WHERE {
  ?person a foaf:Person .
  ?person foaf:name ?name .
  OPTIONAL { ?person foaf:nick ?nick . }
  OPTIONAL { ?person foaf:homepage ?homepage . }
  FILTER (REGEX(STR(?person), "^http://api.talis.com/stores/wod-pd-sandbox/items/People/"))
}

Browsing Yves

... in Tabulator and Marbles

Who knows whom?

SELECT *
WHERE {
  ?person1 foaf:knows ?person2 .
  FILTER (REGEX(STR(?person1), "^http://api.talis.com/stores/wod-pd-sandbox/items/People/"))
}

Extracting the foaf:knows statements

PREFIX foaf: <http://xmlns.com/foaf/0.1/>
CONSTRUCT {
  ?person1 foaf:knows ?person2 .
}
WHERE {
  ?person1 foaf:knows ?person2 .
  FILTER (REGEX(STR(?person1), "^http://api.talis.com/stores/wod-pd-sandbox/items/People/"))
}

Link

Extracting descriptions of all people

PREFIX foaf: <http://xmlns.com/foaf/0.1/>
DESCRIBE ?person
WHERE {
  ?person a foaf:Person .
  FILTER (REGEX(STR(?person), "^http://api.talis.com/stores/wod-pd-sandbox/items/People/"))
}

Link

Showing all people in Exhibit

Go to Babel, select from RDF/XML to Exhibit JSON, then the data is on some web sites, paste the URI from the link above, and click Retrieve and Preview

Mashing up some data

Country data

http://dowhatimean.net/wod-pd/countries.n3

Country data converted to RDF/XML using Triplr

http://triplr.org/rdf/dowhatimean.net/wod-pd/countries.n3

Combining this with the people data in Exhibit

Go to Babel, select from RDF/XML to Exhibit JSON, then the data is on some web sites and Add Another URL, paste the the link to the People RDF and the link to the Countries RDF, and click Retrieve and Preview

RDF data formats

MIME types

RDF/XML

application/rdf+xml

N3

text/rdf+n3; charset=utf-8

N-Triples

text/plain

SPARQL results in XML

application/sparql-results+xml

SPARQL results in JSON

application/sparql-results+json

Using cURL to look up URIs