Querying Linked Data on Android

Querying Linked Data on
Android
Module 2 adaptation for Android
enabled devices
07.04.2014 1

Outline
• This document complements to webinar
Module 2: Querying Linked Data
• It targets querying linked data on mobile
(Android) devices
• Original queries modified to correspond to
limited resources environments
• Triple store implementation by Ontos AG
(http:// www.ontos.com)
07.04.2014 2

Webinar Structure
• OntoQuad installation instructions
• Deployment of preloaded dataset in
OntoQuad
• Running sample queries against the
OntoQuad SPARQL endpoint
07.04.2014 3

OntoQuad Installation
• RDF store for Android
• Detailed setup instructions already provided
by Ontos AG (attached)
• Fresh installations should be started at least
once to initialize their data directory
structures
• OntoQuad should be completely stopped
before deploying preloaded datasets (next
slides)
07.04.2014 4

Prebuild dataset deployment
• Musicbrainz dataset extract
– 5 million RDF triples subset
– No special hardware requirements (<1GB
external storage)
– Sufficient deployment and query response
times
– Still representative for demonstration and
educational purposes
07.04.2014 5

Prebuild dataset setup
• Download the binary files archive
(musicbrainz-5m-bin.zip) on your PC
• Extract the archive on the local file system
– Important files and folders: ./vm, ./txlogs,
.universe, .commands
• Ensure OntoQuad in not active/running
before performing the next steps
07.04.2014 6

Prebuild dataset setup (2)
• Connect the mobile device via appropriate
USB cable to PC and overwrite the
existing files in folder:
/storage/extSdCard/margot/ with the ones
from the archive
• Disconnect the mobile device and start the
OntoQuad server
07.04.2014 7

Setup Verification
• Start the Admin Console and select the
SPARQL section (it will take some time)
• Execute the following query:
SELECT (COUNT(?s) as ?count)
WHERE { ?s ?p ?o }
• The result count value should be
approximately 5 million
07.04.2014 8

Module 2 for Android
• Based on original Webinar Module 2
content
• SPARQL queries adapted for the extracted
data set and the current implementation
limitations
• Each query description refers to the
original location in the Module 2
presentation
07.04.2014 9

Module 2 for Android (2)
• What albums did Queen make (slide 15) ?
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
PREFIX dc: <http://purl.org/dc/elements/1.1/>
PREFIX mo: <http://purl.org/ontology/mo/>
SELECT ?album
WHERE {
?band foaf:name "Queen" .
?band foaf:made ?album .
?album a mo:Release ; dc:title ?title
}
ORDER BY ?title
07.04.2014 10

• What albums and tracks did Queen make
(slide 22) ?
SELECT ?album_name ?track_title
WHERE {
?album dc:title ?album_name ;
mo:record ?record .
?record mo:track ?track .
?track dc:title ?track_title . }
07.04.2014 11

• Retrieve the albums and tracks recorded by Queen,
where the duration of the song is more than 300 secs.
and no longer than 400 secs (slide 23)
SELECT ?album_name ?track_title ?duration
WHERE {
mo:record ?record .
?track dc:title ?track_title ;
mo:duration ?duration;
FILTER (?duration > 300000 && ?duration < 400000) }
07.04.2014 12

• Retrieve the name of the albums recorded by
Queen which have at least two different
songs (slide 24)
SELECT DISTINCT ?album_name
WHERE {
mo:record ?record .
?record mo:track ?track1 .
?record mo:track ?track2 .
FILTER (?track1 != ?track2) }
07.04.2014 13

• Retrieve the duration of the albums recorded by
Queen (slide 25)
SELECT ?album ?album_name (SUM(?track_duration) AS ?album_duration)
WHERE {
?album mo:record ?record ;
dc:title ?album_name.
?track mo:duration ?track_duration .
}
GROUP BY ?album ?album_name
HAVING (SUM(?track_duration) > 3600000)
07.04.2014 14

• Create the dc:creator descriptions for albums
and their tracks recorded by Queen (slide
29)*
PREFIX dbpedia: <http://dbpedia.org/resource/>
CONSTRUCT {
?album dc:creator ?band .
?track dc:creator ?band .}
WHERE {
?album mo:record ?record .
?record mo:track ?track . }
*Note: CONSTRUCT queries might not work properly with the current implementation
07.04.2014 15

• Create the dc:creator descriptions of the
albums recorded by Queen whose title
contains the word 'rock’ (slide 31)*
CONSTRUCT { ?album dc:creator ?band }
WHERE {
?album dc:title ?album_name .
FILTER (REGEX(?album_name, ".*rock.*", "i"))
}
*Note: CONSTRUCT queries might not work properly with the current implementation
07.04.2014 16

Module 2 for Android
Thank you!
07.04.2014 17

Querying Linked Data on Android

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