Internet Technologies

1
Internet Technologies

• Making Queries on RDF

2
Two Approaches

• SPARQL
• - Simple Protocol And RDF Query
• Language
• - Looks like SQL
• - Used by Dbpedia
• MQL
• - Metaweb Query Language
• - Based on JSON
• - Used by Freebase

Both freebase and Dbpedia make their statements
available in RDF.
3
Todays Lecture

• A brief look at SPARQL
• A brief look at MQL

4
SPARQL

• SPARQL Simple Protocol and RDF Query Language
• W3C Recommendation January 2008
• Queries written using Turtle - Terse RDF Triple
  Language
• Download Jena and ARQ Query Engine
• For Ruby, see ActiveRDF

5
SPARQL

• Three specifications
• (1) A query language
• (2) A query results XML format
• (3) A WSDL 2.0 Data Access
• Protocol using HTTP and SOAP
• SPARQL is read only and cannot
• modify the RDF data

6
Input

• lt?xml version"1.0" encoding"UTF-8"?gt
• ltrdfRDF xmlnsrdf"http//www.w3.org/1999/02/22-r
  df-syntax-ns"
• xmlnsfoaf"http//xmlns.com/foaf/0.1/"
• xmlnsrdfs"http//www.w3.org/2000/01/rdf
  -schema"
• xmlnsrss"http//purl.org/rss/1.0/"
• xmlnsdc"http//purl.org/dc/elements/1.1
  /"
• xmlnshtml"http//www.w3.org/1999/xhtml"
  gt
• ltfoafAgent rdfnodeID"id2246040"gt
• ltfoafnamegtJohn Barstowlt/foafnamegt
• ltrdftype rdfresource"http//xmlns.com/foaf/0
  .1/Person"/gt
• ltfoafwebloggt
• ltfoafDocument rdfabout"http//www.nzlinux
  .org.nz/blogs/"gt
• ltdctitlegtVisions of Aestia by John
  Barstowlt/dctitlegt
• ltrdfsseeAlsogt
• ltrsschannel rdfabout"http//www.nzl
  inux.org.nz/blogs/wp-rdf.php?cat9"gt
• ltfoafmaker rdfnodeID"id2246040"/
  gt
• ltfoaftopic rdfresource"http//ww
  w.w3.org/2001/sw/"/gt
• ltfoaftopic rdfresource"http//ww
  w.w3.org/RDF/"/gt
• lt/rsschannelgt

This is shortblogger.xml The file bloggers.xml
has many bloggers.
7
Processing

• PREFIX foaf lthttp//xmlns.com/foaf/0.1/gt
• SELECT ?url
• FROM ltshortblogger.xmlgt
• WHERE
• ?contributor foafname "John Barstow" .
• ?contributor foafweblog ?url .

Stored in a file called ex1.rq
8
Output

• sparql --query ex1.rq
• ------------------------
• url
• lthttp//www.nzlinux.org.nz/blogs/gt
• --------------------------------------------

9
Processing

• PREFIX foaf lthttp//xmlns.com/foaf/0.1/gt
• PREFIX rdf lthttp//www.w3.org/1999/02/22-rdf-syn
  tax-nsgt
• SELECT ?url
• FROM ltshortblogger.xmlgt
• WHERE
• ?contributor rdftype foafPerson .
• ?contributor foafweblog ?url .

Output sparql --query ex2.rq ---------------------
---- url
lthttp//www.nzlinux.org.nz/blo
gs/gt -------------------------
10
Processing

• PREFIX foaf lthttp//xmlns.com/foaf/0.1/gt
• PREFIX rdf lthttp//www.w3.org/1999/02/22-rdf-syn
  tax-nsgt
• SELECT ?x ?n
• FROM ltbloggers.xmlgt
• WHERE
• ?contributor rdftype foafPerson .
• ?contributor foafweblog ?x .
• ?contributor foafname ?n

All three conditions must be satisfied to match
the query.
11
Output

• sparql --query ex4.rq
• --------------------------------------------------
  ------------------------------------
• x
  n
  
• lthttp//www.picklematrix.net/semergence/gt
  "Seth Ladd"
• lthttp//www.wasab.dk/morten/blog/gt
  "Morten Frederiksen"
• lthttp//www.lassila.org/blog/gt
  "Ora Lassila"
• lthttp//people.w3.org/dom/gt
  "Hazaël-Massieux"
• lthttp//xmlarmyknife.org/blog/gt
  "Leigh Dodds"
• lthttp//blogs.sun.com/bblfish/gt
  "Henry Story"
• lthttp//jeenbroekstra.blogspot.com/gt
  "Jeen Broekstra"
• lthttp//people.w3.org/djweitzner/blog/?cat8gt
  "Danny Weitzner"
• lthttp//danbri.org/words/gt
  "Dan Brickley"

12
Processing

• PREFIX foaf lthttp//xmlns.com/foaf/0.1/gt
• PREFIX rdf lthttp//www.w3.org/1999/02/22-rdf-syn
  tax-nsgt
• SELECT DISTINCT ?n
• FROM ltbloggers.xmlgt
• WHERE
• ?contributor foafname ?n

Output -----------------------------------------
n
Mike McCarthy"
"Pasquale Popolizio" "Dean
Allemang"
13
Processing

• PREFIX foaf lthttp//xmlns.com/foaf/0.1/gt
• PREFIX rdf lthttp//www.w3.org/1999/02/22-rdf-syn
  tax-nsgt
• SELECT DISTINCT ?n
• FROM ltbloggers.xmlgt
• WHERE
• ?contributor foafname ?n
• ORDER BY ?n

---------------------- n
"Alexandre Passant"
"Alistair Miles" "Andrew
Matthews" "Benjamin Nowack"
14
Semi-Structured Data

• Definition
• If two nodes of the same type are
• allowed to hold different sets of
• properties the data is called semi-structured.
• SPARQL uses the OPTIONAL keyword to process
  semi-structured data.

15
Processing

• PREFIX foaf lthttp//xmlns.com/foaf/0.1/gt
• PREFIX rdf lthttp//www.w3.org/1999/02/22-rdf-syn
  tax-nsgt
• SELECT DISTINCT ?n ?interest
• FROM ltbloggers.xmlgt
• WHERE
• ?contributor foafname ?n .
• OPTIONAL
• ?contributor foafinterest ?interest
• ORDER BY ?n

"Tetherless World Constellation group RPI"
lthttp//www.w3.org/2001/sw/gt "Tetherless World
Constellation group RPI" lthttp//www.w3.org/RDF/gt
"Tim Berners-Lee"
"Uldis Bojars" lthttp//www.w3.org/2001/sw/
gt "Uldis Bojars" lthttp//www.w3.org/RDF/gt

16
Generating XML

• PREFIX foaf lthttp//xmlns.com/foaf/0.1/gt
• PREFIX rdf lthttp//www.w3.org/1999/02/22-rdf-syn
  tax-nsgt
• SELECT ?n
• FROM ltshortblogger.xmlgt
• WHERE
• ?contributor foafname ?n .

17
From The Command Line

• sparql --query ex8.rq --results rs/xml
• lt?xml version"1.0"?gt
• ltsparql
• xmlnsrdf"http//www.w3.org/1999/02/22-rdf-sy
  ntax-ns"
• xmlnsxs"http//www.w3.org/2001/XMLSchema"
• xmlns"http//www.w3.org/2005/sparql-results"
  gt
• ltheadgt
• ltvariable name"n"/gt
• lt/headgt
• ltresultsgt
• ltresultgt
• ltbinding name"n"gt
• ltliteralgtJohn Barstowlt/literalgt
• lt/bindinggt
• lt/resultgt
• lt/resultsgt
• lt/sparqlgt

18
MQL

• Metaweb Query Language
• Make queries against the freebase data store.
• The input and outputs are JSON strings.

19
Using MQL In A URL
Example from the MQL documentation. Enter the
following in your browser https//api.freebase.c
om/api/service/mqlread?query querytype/m
usic/artist,nameThe Police,album
This is a query to freebase represented in JSON.
20
Output

• "code" "/api/status/ok",
• "result"
• "album"
• "Outlandos
  d'Amour",
• "Reggatta de
  Blanc",
• "Zenyatt\u00e0
  Mondatta
• "The Police Live!"
  ,
• "name" "The Police",
• "type" "/music/artist"
• ,
• "status" "200 OK",
• "transaction_id"cachecache03.p01.sjc1
  81012011-10-13T15

Many more albums in the real query result.
21
Another look at the query.

• "query"
• "type""/music/artist",
• "name""The Police",
• "album"

22
Use The Query Editor

• http//www.freebase.comqueryeditor