Mon norton tut_queryinglinkeddata02

Querying Linked Data

Presented by: Barry Norton

Motivation: Music!

2

Visualiza6on Module

Metadata Streaming providers

Physical Wrapper

Downloads

Data acquisi6

on D2R Transf. LD Wrapper

Musical Content

Applica6

on

Analysis & Mining Module

LD Dataset

Access

LD Wrapper

RDF/ XML

Integrated Dataset

Interlinking Cleansing Vocabulary Mapping

SPARQL Endpoint

Publishing

RDFa

Other content

Agenda 1.   Introduc+on to SPARQL

2.   Querying Linked Data with SPARQL

3.   SPARQL Algebra

4.   Upda+ng Linked Data with SPARQL 1.1

5.   SPARQL Protocol

6.   Reasoning over Linked Data

3 EUCLID -‐ Querying Linked Data

INTRODUCTION TO SPARQL

EUCLID -‐ Querying Linked Data 4

SPARQL


Seman6c Web Stack Berners-‐Lee (2006)

* Protocol and RDF Query Language

Declara6ve query language

SPARQL


•  SPARQL Query –  Declara6ve query language for RDF data –  h\p://www.w3.org/TR/rdf-‐sparql-‐query/

•  SPARQL Algebra –  Standard for communica6on between SPARQL services and clients –  h\p://www.w3.org/2001/sw/DataAccess/rq23/rq24-‐algebra.html

•  SPARQL Update –  Declara6ve manipula6on language for RDF data –  h\p://www.w3.org/TR/sparql11-‐update/

•  SPARQL Protocol –  Standard for communica6on between SPARQL services and clients –  h\p://www.w3.org/TR/sparql11-‐protocol/

SPARQL Query 1.1


•  SPARQL 1.0 only allows accessing the data (query) •  SPARQL 1.1 introduces:

Query extensions

Updates

•  Data management: Insert, Delete, Delete/Insert

•  Graph management: Create, Load, Clear, Drop, Copy, Move, Add

•  Aggregates, Subqueries, Nega6on, Expressions in the SELECT clause, Property paths, assignment, short form for CONSTRUCT, expanded set of func6ons and operators

Federa6on extension •  Service, values, service variables (informa6ve) CH 5

SPARQL Basics


•  RDF triple: Basic building block, of the form subject, predicate, object. Example:

•  RDF triple paNern: Contains one or more variables. Examples:

•  RDF quad paNern: Contains graph name: URI or variable. Examples:

dbpedia:The_Beatles foaf:name "The Beatles" .

dbpedia:The_Beatles foaf:made ?album. ?album mo:track ?track . ?album ?p ?o .

GRAPH <:g> {:s :p :o .} GRAPH ?g {dbpedia:The_Beatles foaf:name ?o.}

SPARQL Basics


•  RDF graph: Set of RDF asser6ons, manipulated as a labeled directed graph.

•  RDF data set: set of RDF triples. It is comprised of: •  One default graph •  Zero or more named graphs

•  SPARQL protocol client: HTTP client that sends requests for SPARQL Protocol opera6ons (queries or updates)

•  SPARQL protocol service: HTTP server that services requests for SPARQL Protocol opera6ons

•  SPARQL endpoint: The URI at which a SPARQL Protocol service listens for requests from SPARQL clients

QUERYING LINKED DATA WITH SPARQL


SPARQL Query


Main idea: PaNern matching •  Queries describe sub-‐graphs of the queried graph •  Graph paNerns are RDF graphs specified in Turtle syntax, which contain variables (prefixed by either “?” or “$”)

•  Sub-‐graphs that match the graph pa\erns yield a result

?album dbpedia: The_Beatles

foaf:made

SPARQL Query


?album dbpedia: The_Beatles

foaf:made

dbpedia: The_Beatles foaf:made

<h\p:// musicbrainz.org/record/...>


foaf:made Data:

Graph pa\ern: Results:

"Help!" "Let It Be"

dc:6tle dc:6tle


"Abbey Road"

dc:6tle

foaf:made

?album

<h\p://musicbrainz.org...>



SPARQL Query


?album

dbpedia: The_Beatles




foaf:made Data:


"Help!" "Let It Be"

dc:6tle dc:6tle


"Abbey Road"

dc:6tle

foaf:made

?album

?+tle

<h\p://...> "Help!"

<h\p://...> "Abbey Road"

<h\p://...> "Let It Be" ?6tle

dc:6tle

SPARQL Query


?album




<h\p:// musicbrainz.org

/track/...>

foaf:made Data:


"Help!" "Help!"

dc:6tle dc:6tle

mo:track

a

mo:Record mo:Track

mo:Record

?album


SPARQL Query: Components


PREFIX dbpedia: <http://dbpedia.org/resource/> 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 FROM <http://musicbrainz.org/20130302> WHERE { dbpedia:The_Beatles foaf:made ?album . ?album a mo:Record ; dc:title ?title } ORDER BY ?title

Prologue: •  Prefix defini6ons •  Subtly different from Turtle syntax -‐ the final period is not used



Query form: •  ASK, SELECT, DESCRIBE or CONSTRUCT •  SELECT retrieves variables and their bindings as a table




Data set specifica+on: •  This clause is op6onal •  FROM or FROM NAMED •  Indicates the sources for the data against which to find matches




Query paNern: •  Defines pa\erns to match against the data •  Generalises Turtle with variables and keywords – N.B. final period op6onal


Solu+on modifier: •  Modify the result set •  ORDER BY, LIMIT or OFFSET re-‐organise rows; •  GROUP BY combines them




Query Forms


SPARQL supports different query forms:

•  ASK tests whether or not a query pa\ern has a solu6on. Returns yes/no

•  SELECT returns variables and their bindings directly

•  CONSTRUCT returns a single RDF graph specified by a graph template

•  DESCRIBE returns a single RDF graph containing RDF data about resource

Query Form: ASK


•  Namespaces are added with the ‘PREFIX’ direc6ve •  Statement pa\erns that make up the graph are specified between brackets (“{}”)

PREFIX dbpedia: <http://dbpedia.org/resource/> PREFIX dbpedia-‐ont: <http://dbpedia.org/ontology/> PREFIX mo: http://purl.org/ontology/mo/ ASK WHERE { dbpedia:The_Beatles mo:member dbpedia:Paul_McCartney.}

Is Paul McCartney member of ‘The Beatles’? Query: true

Results:

Is Elvis Presley member of ‘The Beatles’? Query: false

Results: PREFIX dbpedia: <http://dbpedia.org/resource/> PREFIX dbpedia-‐ont: <http://dbpedia.org/ontology/> PREFIX mo: http://purl.org/ontology/mo/ ASK WHERE { dbpedia:The_Beatles mo:member dbpedia:Elvis_Presley.}

Query Form: SELECT


•  The solu6on modifier projec+on nominates which components of the matches should be returned

•  “*” means all components should be returned

PREFIX dbpedia: <http://dbpedia.org/resource/> 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_name ?track_title WHERE { dbpedia:The_Beatles foaf:made ?album . ?album dc:title ?album_name ; mo:track ?track . ?track dc:title ?track_title .}

Query: What albums and tracks did ‘The Beatles’ make?

Filter expressions •  Different types of filters and func6ons may be used

Query Form: SELECT (2)


PREFIX dbpedia: <http://dbpedia.org/resource/> 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_name ?track_title ?date ?duration WHERE { dbpedia:The_Beatles foaf:made ?album . ?album dc:title ?album_name ; mo:track ?track . ?track dc:title ?track_title ;

mo:duration ?duration; FILTER (?duration>300000 && ?duration<400000) }

Query: Filter: Comparison and logical operators

Retrieve the albums and tracks recorded by ‘The Beatles’, where the duraCon of the song is more than 300 secs. and no longer than 400 secs.



Elimina+on of duplicates

PREFIX dbpedia: <http://dbpedia.org/resource/> 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 MODIFIER ?album_name WHERE { dbpedia:The_Beatles foaf:made ?album . ?album dc:title ?album_name .

mo:track ?track1 . mo:track ?track2 . FILTER (?track1 != ?track2) }

Retrieve the name of the albums recorded by ‘The Beatles’ which have at least two different songs. Query:

?album

“Revolver”

“Sessions”

“Abbey Road”

?album

“Revolver”

“Revolver”

“Revolver”

“Sessions”

“Abbey Road”

“Abbey Road”

DISTINCT

Results:

REDUCED MODIFIER= MODIFIER=

Aggregates

•  Calculate aggregate values: COUNT, SUM, MIN, MAX, AVG, GROUP_CONCAT and SAMPLE

•  Built around the GROUP BY operator •  Prune at group level (cf. FILTER) using HAVING



PREFIX dbpedia: <http://dbpedia.org/resource/> PREFIX foaf: <http://xmlns.com/foaf/0.1/> PREFIX mo: <http://purl.org/ontology/mo/> SELECT ?album (SUM(?track_duration) AS ?album_duration) WHERE { dbpedia:The_Beatles foaf:made ?album . ?album mo:track ?track . ?track mo:duration ?track_duration . } GROUP BY ?album HAVING (SUM(?track_duration) > 3600000)

Retrieve the duraCon of the albums recorded by ‘The Beatles’. Query:

Query Form: DESCRIBE


Takes the resources within the solu6on, and provides informa6on about them as RDF statements. They can be iden6fied by:

•  Specifying explicit IRIs

•  Bindings of variables in the WHERE clause

PREFIX dbpedia: <http://dbpedia.org/resource/> PREFIX mo: <http://purl.org/ontology/mo/> DESCRIBE ?member WHERE { dbpedia:The_Beatles mo:member ?member .}

PREFIX dbpedia: <http://dbpedia.org/resource/> DESCRIBE dbpedia:Paul_McCartney


•  CONSTRUCT WHERE: In order to query for a subgraph, without change, it is no longer necessary to repeat the graph pa\ern in the template

PREFIX dbpedia: <http://dbpedia.org/resource/> PREFIX foaf: <http://xmlns.com/foaf/0.1/> PREFIX mo: <http://purl.org/ontology/mo/> PREFIX dc: <http://purl.org/dc/elements/1.1/> CONSTRUCT WHERE { dbpedia:The_Beatles foaf:made ?album . ?album mo:track ?track .}

Example:

Query Form: CONSTRUCT

Query Form: CONSTRUCT (2a)





foaf:made Data:

Query: Result:

"Help!" "Let It Be"

dc:6tle dc:6tle


"Abbey Road"

dc:6tle

foaf:made

CONSTRUCT { ?album dc:creator dbpedia:The_Beatles .} WHERE { dbpedia:The_Beatles foaf:made ?album .}


<h\p:// musicbrainz

…>

<h\p:// musicbrainz

…> <h\p://

musicbrainz…>

dc:creator

dc:creator

dc:creator


•  Returns RDF statements created from variable bindings

•  Template: graph pa\ern with variables from the query pa\ern

PREFIX dbpedia: <http://dbpedia.org/resource/> PREFIX foaf: <http://xmlns.com/foaf/0.1/> PREFIX mo: <http://purl.org/ontology/mo/> PREFIX dc: <http://purl.org/dc/elements/1.1/> CONSTRUCT { ?album dc:creator dbpedia:The_Beatles . ?track dc:creator dbpedia:The_Beatles .} WHERE { dbpedia:The_Beatles foaf:made ?album . ?album mo:track ?track .}

Create the dc:creator descripCons for albums and their tracks recorded by ‘The Beatles’. Query:

Query Form: CONSTRUCT (2b)

Query Form: CONSTRUCT (3)


Subsets of results •  It is possible to combine the query with solu+on modifiers

(ORDER BY, LIMIT, OFFSET)

PREFIX dbpedia: <http://dbpedia.org/resource/> PREFIX foaf: <http://xmlns.com/foaf/0.1/> PREFIX mo: <http://purl.org/ontology/mo/> PREFIX dc: <http://purl.org/dc/elements/1.1/> CONSTRUCT { ?album dc:creator dbpedia:The_Beatles . ?track dc:creator dbpedia:The_Beatles .} WHERE { dbpedia:The_Beatles foaf:made ?album . ?album mo:track ?track ; dc:date ?date . } ORDER BY DESC(?date) LIMIT 10

Create the dc:creator descripCons for the 10 most recent albums and their tracks recorded by ‘The Beatles’. Query:

Union Graph PaNern •  Allows the specifica6on of alterna6ves (disjunc6ons)


PREFIX dbpedia: <http://dbpedia.org/resource/> PREFIX foaf: http://xmlns.com/foaf/0.1/ PREFIX dc: <http://purl.org/dc/elements/1.1/> CONSTRUCT { ?album dc:creator dbpedia:The_Beatles . ?track dc:creator dbpedia:The_Beatles .} WHERE { dbpedia:The_Beatles foaf:made ?album . ?album dc:title ?album_name . {?album dbpedia-‐ont:recordedIn dbpedia:Abbey_Road_Studios .}

UNION {?album dbpedia-‐ont:recordedIn dbpedia:Trident_Studios .}}

Create the dc:creator descripCons for the albums recorded by ‘The Beatles’ in ‘Abbey Road Studios’ or ‘Trident Studios’ Query:


Filter expressions •  Different types of filters and func6ons may be used


PREFIX dbpedia: <http://dbpedia.org/resource/> PREFIX foaf: <http://xmlns.com/foaf/0.1/> PREFIX dc: <http://purl.org/dc/elements/1.1/> CONSTRUCT {?album dc:creator dbpedia:The_Beatles .} WHERE { dbpedia:The_Beatles foaf:made ?album . ?album dc:title ?album_name ; FILTER (REGEX(?album_name, ".*love.*", i)) }

Query: Filter: Regular expressions over strings

Create the dc:creator descripCons of the albums recorded by ‘The Beatles’ whose Ctle contains the word ‘love .


Type of func+on Func+on Result type

Func6onal Forms

bound IF COALESCE NOT EXISTS, EXISTS or, and RDFTerm-‐equal (=), sameTerm IN, NOT IN

xsd:boolean rdfTerm rdfTerm xsd:boolean xsd:boolean xsd:boolean boolean

Func6ons on RDF Terms

isIRI, isBlank, isLiteral, isNumeric str, lang, datatype IRI BNODE

xsd:boolean simple literal iri iri blank node

Func6ons on Numerics ABS, ROUND, CEIL, FLOOR RAND

numeric xsd:double

Filter expressions

EUCLID -‐ Querying Linked Data 33 Source:h\p://www.w3.org/TR/sparql11-‐query/#SparqlOps


Type of func+on Func+on Result type

Func6ons on Strings STRLEN SUBSTR, UCASE, LCASE STRSTARTS, STRENDS, CONTAINS STRBEFORE, STRAFTER ENCODE_FOR_URI CONCAT langMatches REGEX REPLACE

xsd:integer string literal xsd:boolean literal simple literal string literal xsd:boolean xsd:boolean string literal

Func6ons on Dates and Times

now year, month, day, hours, minutes seconds 6mezone tz

xsd:dateTime xsd:integer xsd:decimal xsd:dayTimeDura6on simple literal

Filter expressions


Source:h\p://www.w3.org/TR/sparql11-‐query/#SparqlOps


Op+onal Graph PaNern •  OPTIONAL clause encloses the op6onal parts •  If variables in the construct clause are not bound in the op6onal,

the triple pa\erns with these variables are not generated


PREFIX foaf: <http://xmlns.com/foaf/0.1/> PREFIX dc: <http://purl.org/dc/elements/1.1/> PREFIX dbpedia-‐owl: <http://dbpedia.org/ontology/> CONSTRUCT { ?album dc:creator ?artist . ?picture dc:depicts ?artist . } WHERE { ?artist foaf:made ?album . OPTIONAL {?artist foaf:depiction ?picture .}}

Create the dc:creator and dc:depicts descripCons of arCsts. Query:


Op+onal Graph PaNern

•  Can test if variables are bound in filter expressions •  Solu6ons that meet the OPTIONAL clause can be filtered out by

using the logical filter NOT (!)


PREFIX foaf: <http://xmlns.com/foaf/0.1/> PREFIX dc: <http://purl.org/dc/elements/1.1/> PREFIX dbpedia-‐owl: <http://dbpedia.org/ontology/> CONSTRUCT { ?album dc:creator ?artist . } WHERE { ?artist foaf:made ?album . OPTIONAL {?artist dbpedia-‐owl:deathPlace ?place_of_death .} FILTER (!BOUND(?place_of_death)) }

Create the dc:creator descripCons of those arCsts who are not dead.

Query:


NOT EXISTS {?artist dbpedia-‐owl:deathPlace ?place_of_death .}

Assigning Variables •  The value of an expression can be added to a solu6on mapping by

binding a new variable (which can be further used and returned) •  The BIND form allows to assign a value to a variable from a BGP


PREFIX dbpedia: <http://dbpedia.org/resource/> PREFIX foaf: <http://xmlns.com/foaf/0.1/> PREFIX mo: <http://purl.org/ontology/mo/> PREFIX dbpedia-‐ont: <http://dbpedia.org/ontology/> CONSTRUCT { ?track dbpedia-‐ont:runtime ?secs .} WHERE { dbpedia:The_Beatles foaf:made ?album . ?album mo:track ?track . ?track mo:duration ?duration . BIND((?duration/1000) AS ?secs) .}

Calculate the duraCon of the tracks from ms to s, and store the value using the dbpedia-‐ont:runCme property .

Query:


Sub-‐queries and Aggregate Values

•  To combine the CONSTRUCT query form with aggregate values, a sub-‐query should be created inside the WHERE clause


PREFIX dbpedia: <http://dbpedia.org/resource/> PREFIX foaf: <http://xmlns.com/foaf/0.1/> PREFIX mo: <http://purl.org/ontology/mo/> CONSTRUCT {?album music-‐ont:duration ?album_duration .} WHERE { SELECT ?album (SUM(?track_duration) AS ?album_duration) { dbpedia:The_Beatles foaf:made ?album . ?album mo:track ?track . ?track mo:duration ?track_duration . } GROUP BY ?album HAVING (SUM(?track_duration) > 3600000)}

Materialize the duraCon of the albums recorded by ‘The Beatles’. Query:


UPDATING LINKED DATA WITH SPARQL 1.1


Data Management


SPARQL 1.1 provides data update opera6ons:

•  INSERT data: adds some triples, given inline in the request, into a graph

•  DELETE data: removes some triples, given inline in the request, if the respec6ve graphs contains those

•  DELETE/INSERT data: uses in parallel INSERT and DELETE

CH 1

CH 1

Data Management (2)


INSERT data

PREFIX dc: <http://purl.org/dc/elements/1.1/> PREFIX foaf: <http://xmlns.com/foaf/0.1/>

INSERT DATA { GRAPH { <http://musicbrainz.org/20130302> <http://musicbrainz.org/artist/b10bbbfc-‐cf9e-‐42e0-‐be17-‐e2c3e1d2600d>

foaf:made <http://musicbrainz.org/release/3a685770-‐7326-‐34fc-‐9f18-‐e5f5626f3dc5> , < http://musicbrainz.org/release/cb6f8798-‐d51e-‐4fa5-‐a4d1-‐2c0602bfe1b6 > .

<http://musicbrainz.org/release/3a685770-‐7326-‐34fc-‐9f18-‐e5f5626f3dc5> dc:title "Please Please Me". < http://musicbrainz.org/release/cb6f8798-‐d51e-‐4fa5-‐a4d1-‐2c0602bfe1b6 >

dc:title "Something New". } }

Insert the following albums recorded by The Beatles into the graph http://musicbrainz.org/20130209-‐004702

CH 1

Data Management (3)


DELETE data Delete all the information about the album Casualities of The Beatles.

PREFIX dc: <http://purl.org/dc/elements/1.1/> PREFIX foaf: <http://xmlns.com/foaf/0.1/>

DELETE { ?album ?predicate ?object . } WHERE { <http://musicbrainz.org/artist/b10bbbfc-‐cf9e-‐42e0-‐be17-‐e2c3e1d2600d>

foaf:made ?album . ?album dc:title "Casualities". ?album ?predicate ?object .}

CH 1

Data Management (4)


DELETE/INSERT data

PREFIX dbpedia: <http://dbpedia.org/resource/> PREFIX db-‐ont: <http://dbpedia.org/ontology/> PREFIX foaf: <http://xmlns.com/foaf/0.1/>

DELETE { dbpedia:The_Beatles db-‐ont:currentMember ?x . } INSERT { GRAPH <http://musicbrainz.org/20130209-‐004702> { dbpedia:The_Beatles db-‐ont:formerBandMember ?x .} } WHERE { dbpedia:The_Beatles db-‐ont:currentMember ?x . ?x foaf:name "Peter Best" .}

Delete the status of ‘Peter Best’ as current member of´The Beatles´, and insert his status as former member of the band.

Graph Management


SPARQL 1.1 provides graph update opera6ons:

•  CREATE: creates an empty graph in the Graph Store

•  LOAD: reads the content of a document into a graph in the Graph Store

•  CLEAR: removes all triples in one or more graphs

•  DROP: removes the graph from the Graph Store

•  Other opera+ons: COPY, MOVE, ADD

Graph Management (2)


CREATE •  Creates a new named graph •  Can be used with the DEFAULT and ALL keywords

LOAD •  An RDF graph can be loaded from a URL

•  LOAD can be used with the SILENT keyword

CREATE GRAPH <http://musicbrainz.org/20130302>

LOAD <http://xmlns.com/foaf/spec/20100809.rdf>

LOAD <http://xmlns.com/foaf/spec/20100809.rdf> INTO <http://xmlns.com/foaf/0.1/>

Named graph



CLEAR •  Removes all triples in the graph (it is emp6ed but not deleted!) •  The graph(s) can be specified with the following keywords:

DEFAULT, NAMED, ALL, GRAPH •  Can be used with the SILENT keyword

DROP •  The given graph is removed from the Graph Store, including its

content •  Can be used with the DEFAULT and ALL keywords

CLEAR GRAPH <http://musicbrainz.org/20130302>

DROP GRAPH <http://musicbrainz.org/20130302>



SPARQL 1.1 provides other graph management opera6ons:

•  COPY … TO …

•  MOVE … TO …

•  ADD … TO …

COPY GRAPH <http://musicbrainz.org/20130302> TO GRAPH <http://musicbrainz.org/20130303>

MOVE GRAPH <http://musicbrainz.org/temp> TO GRAPH <http://musicbrainz.org/20130303>

ADD GRAPH <http://musicbrainz.org/20130302> TO GRAPH <http://musicbrainz.org/20130303>

SPARQL PROTOCOL FOR RDF


SPARQL 1.1. Protocol


•  Consists of two opera+ons: query and update

•  An opera6on defines: •  The HTTP method (GET or POST) •  The HTTP query string parameters •  The message content included in the HTTP request body •  The message content included in the HTTP response body

SPARQL Client SPARQL Endpoint Request

alt [no errors]!

[else]!

Success Response

Failure Response


•  Sends a SPARQL query to a service and receives the results of the query

•  The response is:

•  May be invoked using HTTP GET or HTTP POST. The method POST with URL encoding is mostly used when the query string is too long

Query Operation

XML, JSON, CSV/TSV from a SELECT query RDF/XML, Turtle from a CONSTRUCT query


Example:

PREFIX dbpedia: <http://dbpedia.org/resource/> PREFIX dbpedia-‐ont: <http://dbpedia.org/ontology/> SELECT ?album WHERE { ?album dbpedia-‐ont:artist dbpedia:The_Beatles .} LIMIT 3

SPARQL Query:

Query Operation (2)

HTTP GET request:

Try this query! (Click on the hurl icon)

Update Operation


•  Sends a SPARQL update request to a service

•  Should be invoked using the HTTP PATCH/POST method

•  The response consists of a HTTP response status code, which indicates success or failure of the opera6on

REASONING OVER LINKED DATA


Reasoning for Linked Data Integration


•  Example: Integra6on of the MusicBrainz data set and the DBpedia data set

Integra+on Data set Data set



mo:b10bbbfc-‐cf9e-‐42e0-‐be17-‐e2c3e1d2600d foaf:name The Beatles; mo:member mo:ba550d0e-‐adac-‐4864-‐b88b-‐407cab5e76af; mo:member mo:4d5447d7-‐c61c-‐4120-‐ba1b-‐d7f471d385b9; mo:member mo:42a8f507-‐8412-‐4611-‐854f-‐926571049fa0; mo:member mo:300c4c73-‐33ac-‐4255-‐9d57-‐4e32627f5e13.

dbpedia:The_Beatles dbpedia-‐ont:origin dbpedia:Liverpool; dbpedia-‐ont:genre dbpedia:Rock_music; foaf:depiction .

Integra+on Data set Data set

same



mo:b10bbbfc-‐cf9e-‐42e0-‐be17-‐e2c3e1d2600d foaf:name The Beatles; mo:member mo:ba550d0e-‐adac-‐4864-‐b88b-‐407cab5e76af; mo:member mo:4d5447d7-‐c61c-‐4120-‐ba1b-‐d7f471d385b9; mo:member mo:42a8f507-‐8412-‐4611-‐854f-‐926571049fa0; mo:member mo:300c4c73-‐33ac-‐4255-‐9d57-‐4e32627f5e13.

dbpedia:The_Beatles dbpedia-‐ont:origin dbpedia:Liverpool; dbpedia-‐ont:genre dbpedia:Rock_music; foaf:depiction .

same

SELECT ?m ?g WHERE { dbpedia:The_Beatles dbpedia-‐ont:genre ?g; mo:member ?m.}

Query: ?m ?g mo:ba550d0e-‐adac-‐4864-‐b88b-‐407cab5e76af

dbpedia:Rock_music

mo:4d5447d7-‐c61c-‐4120-‐ba1b-‐d7f471d385b9

dbpedia:Rock_music

mo42a8f507-‐8412-‐4611-‐854f-‐926571049fa0;

dbpedia:Rock_music

mo300c4c73-‐33ac-‐4255-‐9d57-‐4e32627f5e13

dbpedia:Rock_music

Result set:

SPARQL 1.1: Entailment Regimes


•  SPARQL 1.0 was defined only for simple entailment (pa\ern matching )

•  SPARQL 1.1 is extended with entailment regimes other than simple entailment: –  RDF entailment –  RDFS entailment –  D-‐Entailment –  OWL RL entailment –  OWL Full entailment –  OWL 2 DL, EL, and QL entailment –  RIF entailment

Source: h\p://www.w3.org/TR/rdf-‐mt/#RDFSRules

RDFS


Resource Descrip+on Framework Schema


Taxonomies and inferences

RDFS Entailment Regimes


•  Contains 13 entailment rules denominated rdfsi for inference over RDFS defini6ons*: –  rdfs:Literal (rdfs1, rdfs13) –  rdfs:domain (rdfs2), rdfs:range (rdfs3)

–  rdfs:Resource (rdfs4a, rdfs4, rdfs8) –  rdfs:subPropertyOf (rdfs5, rdfs6, rdfs7, rdfs12) –  rdfs:Class (rdfs8, rdfs10) –  rdfs:subClassOf (rdfs9, rdfs10, rdfs11) –  rdfs:ContainerMembershipProperty (rdfs12) –  rdfs:Datatype (rdfs13)

* Source: h\p://www.w3.org/TR/rdf-‐mt/#RDFSRules

rdfs2 – rdfs:domain



dbpedia: Paul_McCartney

SELECT ?x WHERE { ?x a mo:MusicGroup.}

mo:member rdfs:domain mo:MusicGroup .

?x ?x

dbpedia:The_Beatles …

mo:member

Schema: Query:

Result set: Result set with inference:

dbpedia: John_Lennon

dbpedia: George_Harrison

dbpedia: Ringo_Starr

mo:member mo:member mo:member

rdfs3 – rdfs:range




SELECT ?x WHERE { ?x a foaf:Agent.}

mo:member rdfs:range foaf:Agent .

?x ?x

dbpedia:Paul_McCartney

dbpedia:John_Lennon

dbpedia:Ringo_Starr

dbpedia:George_Harrison …

dbpedia-‐ont: bandMember

Schema: Query:








rdfs7 – rdfs:subPropertyOf


dbpedia: Yesterday


SELECT ?x WHERE { dbpedia:Yesterday mo:performer ?x.}

mo:singer rdfs:subPropertyOf mo:performer .

?x

dbpedia:John_Lennon

dbpedia:Ringo_Starr

dbpedia:George_Harrison

?x

dbpedia:John_Lennon

dbpedia:Ringo_Starr



mo:singer

Schema: Query:





mo:performer mo:performer mo:performer

mo:performer

rdfs9 – rdfs:subClassOf



SELECT ?x WHERE { ?x a mo:MusicArtist.}

mo:MusicGroup rdfs:subClassOf mo:MusicArtist .

?x ?x

dbpedia:The_Beatles …

Schema: Query:


mo: MusicAr6st

rdf:type

mo: MusicGroup

rdf:type

Inference from Schema


•  Knowledge encoded in the schema leads to infer new facts

•  This is also captured in the set of axioma+c triples, which provide basic meaning for all the vocabulary terms

mo:MusicGroup rdfs:subClassOf mo:MusicArtist . mo:MusicGroup a rdfs:Class . mo:MusicArtist a rdfs:Class .

Schema:

Inferred facts:

rdfs:subClassOf rdfs:domain rdfs:Class .

rdfs:subClassOf rdfs:range rdfs:Class .

RDFS: Lack of Consistency Check


•  It is possible to infer facts that seem incorrect facts, but RDFS cannot prevent this:

Schema: mo:member rdfs:domain mo:MusicGroup ; rdfs:range foaf:Agent .

Exis6ng :PaulMcCartney a :SoloMusicArtist ; facts: :member :TheBeatles . Inferred :PaulMcCartney a :MusicGroup . facts: No contradic+on!:

The mis-‐modeling is not diagnosed

rdfs2

•  We might wish further inferences, but these are beyond the entailment rules implemented by RDFS

RDFS: Inference Limitations


foaf:knows rdfs:domain foaf:Person ; rdfs:range foaf:Person .

foaf:made rdfs:domain foaf:Agent . :PaulMcCartney foaf:made :Yesterday ; foaf:knows :RingoStarr . :PaulMcCartney a foaf:Agent ; a foaf:Person . :RingoStarr a foaf:Person .

Schema:

Existing fact:

Inferred facts:

:Yesterday dc:creator :PaulMcCartney. :RingoStarr foaf:knows :PaulMcCartney .

These inferences require OWL!

NOT inferred:

Cannot model with RDFS that ‘x knows y’ implies ‘y knows x’

Cannot model with RDFS that if ‘x makes y’ implies that ‘the creator of y is x’

OWL


Web Ontology Language


Ontologies and inferences

Introduction to OWL


•  Provides more ontological constructs and avoids some of the poten6al confusion in RDFS

•  OWL 2 is divided into sub-‐languages denominated profiles: –  OWL 2 EL: Limited to basic classifica6on, but with polynomial-‐6me reasoning

–  OWL 2 QL: Designed to be translatable to rela6onal database querying

–  OWL 2 RL: Designed to be efficiently implementable in rule-‐based systems

•  Most triple stores concentrate on the use of RDFS with a subset of OWL features, called OWL-‐Horst or RDFS++

More restric6ve than OWL DL

OWL Properties


OWL dis6nguishes between two types of proper6es: •  OWL ObjectProper+es: resources as values •  OWL DatatypeProper+es: literals as values

:plays rdf:type owl:ObjectProperty;

rdfs:domain :Musician; rdfs:range :Instrument . :hasMembers rdf:type owl:DatatypeProperty; rdfs:domain :MusicGroup

rdfs:range xsd:int .

Property Axioms


•  Property axioms include those from RDF Schema •  OWL allows for property equivalence. Example: EquivalentObjectProperties(dbpedia-‐ont:bandMember mo:member) dbpedia-‐ont:bandMember owl:equivalentProperty mo:member.

≡



mo:member




mo:member

mo:member

mo:member

SELECT ?x {dbpedia:The_Beatles dbpedia-‐ont:bandMember ?x.}

Query:

?x Result set:

?x dbpedia:Paul_McCartney

dbpedia:John_Lennon

dbpedia:Ringo_Starr


Result set with inference:

Property Axioms


•  Property axioms include those from RDF Schema •  OWL allows for property equivalence. Example: EquivalentObjectProperties(dbpedia-‐ont:bandMember mo:member) dbpedia-‐ont:bandMember owl:equivalentProperty mo:member.

•  OWL allows for property disjointness. Example: DisjointObjectProperty(dbpedia-‐ont:length mo:duration)

dbpedia-‐ont:length owl:propertyDisjointWith mo:duration.

•  There is no standard for implemen6ng inconsistency reports under SPARQL

≡

≡

Property Axioms (2)


OWL allows the defini6on of property characteris6cs to infer new facts rela6ng to instances and their proper6es

•  Symmetry

•  Transi6vity •  Inverse •  Func6onal •  Inverse Func6onal

Property Axioms: Symmetry



dbpedia: Billy_Preston

dbpedia: Plas6c_Ono_

Band :associatedMusicalArtist a owl:SymmetricProperty .

?genre

dbpedia:Plastic_Ono_Band

?genre

dbpedia:Plastic_Ono_Band

dbpedia:Billy_Preston

:associatedMusicalArtist

Schema:


SELECT ?x WHERE { dbpedia:The_Beatles :associatedMusicalArtist ?x.}

Query:

:associatedMusicalArtist

Property Axioms: Transitivity


:Rock

:Heavy_ metal

:Black_ metal

:Punk_ rock SELECT ?genre WHERE {

:Rock :subgenre ?genre .}

:subgenre a owl:TransitiveProperty .

?genre

:Heavy_metal

:Punk_rock

?genre

:Heavy_metal

:Punk_rock

:Black_metal

:subgenre :subgenre

:subgenre :subgenre

Schema:

Query:


Property Axioms: Inverse


SELECT ?x WHERE { ?x mo:member_of dbpedia:The_Beatles .}

mo:member_of owl:inverseOf mo:member.

?x

dbpedia:John_Lennon


?x

dbpedia:John_Lennon



dbpedia:Ringo_Starr

Schema:

Query:




mo:member_of




mo:member

mo:member_of

mo:member

mo:member_of mo:member_of

Example: Every ar6st primarily plays only one musical instrument mo:primary_instrument rdf:type owl:FunctionalProperty . dbpedia:Jimi_Hendrix mo:primary_instrument dbpedia:Electric_Guitar. dbpedia:Jimi_Hendrix mo:primary_instrument dbpedia:E-‐Guitar. Conclusion dbpedia:Electric_Guitar owl:sameAs dbpedia:E-‐Guitar .

Property Axioms: Functional


It refers to a property that can have only one (unique) value for each instance

r2

mo:primary_

instrument

same

r1

mo:primary_ instrument

Example: Every recording has a unique ISRC (Interna6onal Standard Recording Code) mo:isrc rdf:type owl:InverseFunctionalProperty . mo:21047249-‐7b3f-‐4651-‐acca-‐246669c081fd mo:isrc "GBAYE6300412" . dbpedia:She_Loves_You mo:isrc "GBAYE6300412" . Conclusion mo:21047249-‐7b3f-‐4651-‐acca-‐246669c081fd

owl:sameAs :dbpedia:She_Loves_You .

Property Axioms: Inverse Functional


It is useful for specifying unique proper6es iden6fying an individual

r2

mo:isrc

mo:isrc same

r1

Individual Axioms


OWL Individuals represent instances of classes. They are related to their class by the rdf:type property

•  We can state that two individuals are the same SameIndividual(<artist/ba550d0e-‐adac-‐4864-‐b88b-‐407cab5e76af#_> dbpedia:PaulMcCartney)�

<artist/ba550d0e-‐adac-‐4864-‐b88b-‐407cab5e76af#_> owl:sameAs dbpedia:PaulMcCartney .

•  We can state that two individuals are different DifferentIndividuals(:TheBeatles_band :TheBeatles_TVseries)

:TheBeatles_band owl:differentFrom :TheBeatles_Tvseries .

≡

≡

Class Axioms


Axioms declare general statements about concepts which are used in logical inference (reasoning). Class axioms:

•  Sub-‐class rela6onship (from RDF Schema)

•  Equivalent rela6onship: classes have the same individuals EquivalentClass(:Musician :MusicArtist)

:Musician owl:equivalentClass :MusicArtist .

•  Disjointness: classes have no shared individuals DisjointClasses(:SoloMusicArtist :MusicGroup) :SoloMusicArtist owl:disjointWith :MusicGroup . ≡

≡

Class Construction


•  OWL classes are defined by the OWL term owl:Class

•  OWL classes can be subclassed as in RDFS:

•  OWL classes may be combined with class constructs to build new classes

Music Ar6st

Ar6st

:MusicArtist rdfs:subClassOf :Artist .

Class Construction (2)


These class constructs are available in OWL, not in RDFS

The class of female music ar6sts ObjectIntersectionOf(:Female :MusicArtist)� [a owl:Class; owl:intersectionOf(:Female :MusicArtist)]

The class of music ar6sts ObjectUnionOf(:SoloMusicArtist :MusicGroup) [a owl:Class; owl:unionOf(:SoloMusicArtist :MusicGroup)]

Everything that’s not instrumental music ObjectComplementOf(:InstrumentalMusic) [a owl:Class; owl:complementOf(:InstrumentalMusic)]

Female

Music Ar6st

Solo

Group

Instrumental

≡

≡

≡ NOTE: Anonymous classes!

Naming Class Constructions


•  Direct naming can be achieved via owl:equivalentClass

•  This construc6on provides necessary and sufficient condi6ons for class membership

•  Class naming can be also achieved using rdfs:subClassOf, it provides a necessary but insufficient condi6on for class membership

Music Ar6st Solo

Group

EquivalentClass(:MusicArtist ObjectUnionOf(:SoloMusicArtist :MusicGroup)) :MusicArtist owl:equivalentClass [owl:unionOf (:SoloMusicArtist :MusicGroup)]

≡

Summary


•  Basic concepts: triple pa\erns, graph pa\erns, SPARQL endpoint ...

•  SPARQL Query: •  Query forms: ASK, SELECT, DESCRIBE, CONSTRUCT

•  Query paNerns: BGP, UNION, OPTIONAL, FILTER

•  Sequence modifiers: DISTINCT, REDUCED, ORDER BY, LIMIT, OFFSET

•  SPARQL 1.1 Update: •  Data management: INSERT, DELETE; DELETE/INSERT

•  Graph management: LOAD, CLEAR, CREATE, DROP, COPY/MOVE/ADD

•  SPARQL Protocol: query opera6on, update opera6on

Que

rying Link

ed Data

In this chapter we studied:

Summary (2)


•  Reasoning over Linked Data: •  SPARQL 1.1 entailment regimes

•  RDFS: entailment regimes, lacks of consistency check, inference limita6ons

•  OWL: proper6es, property axioms (symmetry, transi6vity, inverse, func6onal, inverse func6onal), individual axioms, class axioms, class construc6ons, naming classes …

Rea

soning

ove

r Linke

d Data

In this chapter we studied:

For exercises, quiz and further material visit our website:

EUCLID -‐ Providing Linked Data 85

@euclid_project euclidproject euclidproject

http://www.euclid-‐project.eu

Other channels:

eBook Course

Acknowledgements

•  Alexander Mikroyannidis •  Alice Carpen6er •  Andreas Harth •  Andreas Wagner •  Andriy Nikolov •  Barry Norton •  Daniel M. Herzig •  Elena Simperl •  Günter Ladwig •  Inga Shamkhalov •  Jacek Kopecky •  John Domingue

•  Juan Sequeda •  Kalina Bontcheva •  Maria Maleshkova •  Maria-‐Esther Vidal •  Maribel Acosta •  Michael Meier •  Ning Li •  Paul Mulholland •  Peter Haase •  Richard Power •  Steffen Stadtmüller

86

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