ESWC SS 2013 - Tuesday Tutorial 1 Maribel Acosta and Barry Norton: Providing Linked Data

Providing
Linked
Data

Presented
by:

Barry
Norton

Maribel
Acosta

Motivation:
Music!

2

Visualiza3on

Module

Metadata

Streaming
providers

Physical
Wrapper

Downloads

Data
acquisi3on

R2R
Transf.
LD
Wrapper

Musical
Content

Applica3on

Analysis
&

Mining
Module

LD
Data
set
Access

LD
Wrapper

RDF/

XML

Integrated

Dataset

Interlinking
Cleansing

Vocabulary

Mapping

SPARQL

Endpoint

Publishing

RDFa

Other
content

LINKED
DATA
LIFECYCLE

EUCLID
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Querying
Linked
Data
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Linked
Data
Principles

1.  Use
URIs
as
names
for
things.

2.  Use
HTTP
URIs
so
that
users
can
look
up

those
names.

3.  When
someone
looks
up
a
URI,
provide

useful
informa9on,
using
the
standards

(RDF*,
SPARQL).

4.  Include
links
to
other
URIs,
so
that
users

can
discover
more
things.

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Providing
Linked
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CH
1

Linked
Data

Lifecycle

Linked
Data
Lifecycle

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Providing
Linked
Data
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Source:
Sören
Auer.
“The
Seman3c
Data
Web”
(slides)

Source:
José
M.
Alvarez.
“My
Linked
Data
Lifecycle”

Source:
Michael
Hausenblas.
“Linked
Data
lifeyclcle”

Core
Tasks
for
Providing

Linked
Data

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Providing
Linked
Data
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Based
on
the
proposed
LD
lifecycles
and
the
LD

principles,
we
can
iden3fy
3
main
tasks
for
providing
LD:

① Crea9ng:
includes
data
extrac3on,
crea3on
of
HTTP

URIs,
and
vocabulary
selec3on.
(LD
principles
1
&
2)

② Interlinking:
involves
the
crea3on
of
(RDF)
links
to

external
data
sets.
(LD
principle
4)

③ Publishing:
consists
of
crea3ng
the
metadata
and

making
the
data
set
accessible.
(LD
principle
3)

Agenda

1.  Crea9ng
Linked
Data

2.  Interlinking
Linked
Data

3.  Publishing
Linked
Data

4.  Linked
Data
publishing
checklist

7
EUCLID
-‐
Providing
Linked
Data

CREATING
LINKED
DATA

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Querying
Linked
Data
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•  The
data
of
interest
may
be
stored
in
a
wide
range
or

formats:

•  Several
tools
support
the
process
of
mining
data

from
diﬀerent
repositories,
for
example:

Extracting
the
Data

9
EUCLID
-‐
Providing
Linked
Data

Spreadsheets

or
tabular
data

Databases
Text

R2RML

Using
the
RDF
Data
Model

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Providing
Linked
Data
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•  The
RDF
data
model
is
used
to
represent
the

extracted
informa3on

•  The
nodes
represent
the
concepts/en33es
within

the
data.
A
node
corresponds
to
a
URI,
a
blank
node

or
a
literal
(only
in
predicates)

•  The
rela3onships
between
the
concepts/en33es
are

modeled
as
arcs

Subject
Object

Predicate

Naming
Things:
URIs

•  All
the
things
or
dis3nct
en33es
within
the
data
must

be
named

•  According
to
the
Linked
Data
principles,
the
standard

mechanism
to
name
en33es
is
the
URI

•  Designing
Cool
URIs:

–  Leave
out
informa3on
about
the
data
regarding
to:
author,

technologies,
status,
access
mechanisms,
…

–  Simplicity:
short,
mnemonic
URIs

–  Stability:
maintain
the
URIs
as
long
as
possible

–  Manageability:
issue
the
URIs
in
a
way
that
you
can
manage

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Providing
Linked
Data

Source:hjp://www.w3.org/TR/cooluris/

Selecting
Vocabularies

•  Vocabularies

model
the
concepts
and
the

rela9onship
between
them
in
a
knowledge
domain

•  Terms
from
well-‐known
vocabularies
should
be

reused
wherever
possible

•  New
terms
should
be
deﬁne
only
if
you
can
not
ﬁnd

required
terms
in
exis3ng
vocabularies

•  A
large
number
of
vocabularies
in
RDF
are
openly

available,
e.g.,
Linked
Open
Vocabularies
(LOV)

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EUCLID
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Providing
Linked
Data

Selecting
Vocabularies
(2)

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Providing
Linked
Data
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Linked
Open
Vocabularies

322
vocabularies

classiﬁed
by
domain

Source:hjp://lov.okfn.org/dataset/lov/

Selecting
Vocabularies
(3)

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Providing
Linked
Data
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Linked
Open
Vocabularies:
Analyzing
MusicOntology

Source:hjp://lov.okfn.org/dataset/lov/details/vocabulary_mo.html

Selecting
Vocabularies
(4)

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Linked
Data
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Other
lists
of
well-‐known
vocabularies
are
maintained

by:

•  W3C
SWEO
Linking
Open
Data
community
project

hjp://www.w3.org/wiki/TaskForces/CommunityProjects/LinkingOpenData/
CommonVocabularies

•  Library
Linked
Data
Incubator
Group:
Vocabularies
in

the
library
domain

hjp://www.w3.org/2005/Incubator/lld/XGR-‐lld-‐vocabdataset-‐20111025

INTERLINKING
LINKED
DATA

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Linked
Data
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Interlinking
Data
Sets

•  It’s
one
of
the
Linked
Data
principles!

•  Involves
the
crea3on
of
RDF
links
between
two

diﬀerent
RDF
data
sets:

–  Links
at
instance
level
(rdfs:seeAlso,
owl:sameAs)

–  Links
at
schema
level
(RDFS
subclass/subproperty,
OWL

equivalent
class/property,
SKOS
mapping
proper9es)

•  Appropriate
links
are
detected
via
link
discovery

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Linked
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4.
Include
links
to
other
URIs,
so
that
users
can
discover

more
things.

Interlinking
Data
Sets
(2)

Challenges
for
link
discovery

•  Linked
Data
sets
are
heterogeneous
in
terms
of

vocabularies,
formats
and
data
representa3on

•  Large
range
of
knowledge
domains

•  Scalability:
LD
is
composed
of
a
large
number
of
data

sets
and
RDF
triples,
hence
it
is
not
possible
to

compare
every
possible
en3ty
pair

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Providing
Linked
Data
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Source:
Robert
Isele.
“LOD2
Webinar
Series:Silk”

Interlinking
Data
Sets
(3)

Challenges
for
link
discovery

•  It
corresponds
to
the
en9ty
resolu9on
problem:

deciding
whether
two
en..es
correspond
to
same
object
in

the
real
world

•  Name
ambigui9es:
typos,
misspellings,
diﬀerent

languages,
homonyms

•  Structural
ambigui9es:
same
concepts/en33es
with

diﬀerent
structures.
Requires
the
applica3on
of
ontology

and
schema
matching
techniques

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Providing
Linked
Data
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Interlinking
Data
Sets
(4)

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Providing
Linked
Data
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RDF
data
sets

can
be
interlinked:

Manually

•  Involves
the
manual
explora3on
of

LD
data
sets
and
their
RDF

resources
to
iden3fy
linking
targets

•  May
not
be
feasible
when
the

number
of
en33es
within
the
data

set
is
very
large

Automatically

•  Using
tools
that
perform
link

discovery
based
on
linkage
rules,
for

example:
Silk,
Limes
and
xCurator

owl:sameAs
&
rdfs:seeAlso

•  owl:sameAs

•  Creates
links
between
individuals

•  States
that
two
URIs
refer
to
the
same
individuals

•  rdfs:seeAlso

•  States
that
a
resource
may
provide
addi3onal
informa3on

about
the
subject
resource

•  Links
in
MusicBrainz:

–  owl:seeAlso
is
used
for
music
ar3sts

–  rdfs:seeAlso
is
used
for
albums

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Linked
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SKOS

•  Simple
Knowledge
Organiza3on
System

–  hjp://www.w3.org/TR/skos-‐reference/

•  Data
model
for
knowledge
organiza3on
systems

(thesauri,
classiﬁca3on
scheme,
taxonomies)

•  SKOS
data
is
expressed
as
RDF
triples

•  Allows
the
crea3on
of
RDF
links
between
diﬀerent

data
sets
with
the
usage
of
mapping
proper9es

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Providing
Linked
Data
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SKOS:
Mapping
Properties

These
proper3es
are
used
to
link
SKOS
concepts

(par3cularly
instances)
in
diﬀerent
schemes:

•  skos:closeMatch:
links
two
concepts
that
are

suﬃciently
similar
(some3mes
can
be
used
interchangeably)

•  skos:exactMatch:
indicates
that
the
two
concepts

can
be
used
interchangeably.

•  Axiom:
It
is
a
transi9ve
property

•  skos:relatedMatch:
states
an
associa3ve
mapping

link
between
two
concepts

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Linked
Data
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Example
of
SKOS
exact
match

SKOS:
Mapping
Properties
(2)

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Linked
Data
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mo:MusicArtist
skos:exactMatch
dbpedia-‐ont:MusicalArtist.

@prefix
skos:
<http://www.w3.org/2004/02/skos/core#>

@prefix
mo:
<http://purl.org/ontology/mo/>

@prefix
dbpedia-‐ont:
<http://dbpedia.org/ontology/>

@prefix
schema:
<http://schema.org/>

mo:MusicGroup
skos:exactMatch
schema:MusicGroup.

mo:MusicGroup
skos:exactMatch
dbpedia-‐ont:Band.

Example
of
SKOS
close
match

SKOS:
Mapping
Properties
(3)

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Linked
Data
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mo:SignalGroup
skos:closeMatch
schema:MusicAlbum.

@prefix
skos:
<http://www.w3.org/2004/02/skos/core#>

@prefix
mo:

@prefix
dbpedia-‐ont:
<http://dbpedia.org/ontology/>

@prefix
schema:
<http://schema.org/>

mo:SignalGroup
skos:closeMatch
dbpedia-‐ont:Album.

Integrity
conditions

•  Guarantee
consistency
and
avoid
contradic3ons
in

the
rela3onships
between
SKOS
concepts

SKOS:
Mapping
Properties
(4)

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Linked
Data
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skos:Mapping

Relation

skos:close

Match

skos:exact

Match

skos:related

Match

Symmetric

&
Transi9ve

Disjoint

with

Par3al
Mapping
Rela3on
diagram
with
integrity
condi3ons

Symmetric

PUBLISHING
LINKED
DATA

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Providing
Linked
Data
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Publishing
Linked
Data

Once
the
RDF
data
set
has
been
created
and

interlinked,
the
publishing
process
involves
the

following
tasks:

1.  Metadata
crea3on
for
describing
the
data
set

2.  Making
the
data
set
accessible

3.  Exposing
the
data
set
in
Linked
Data
repositories

4.  Valida9ng
the
data
set

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Linked
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•  Consists
of
providing
(machine-‐readable)
metadata

of
RDF
data
sets
which
can
be
processed
by
engines

•  This
informa3on
allows
for:

–  Eﬃcient
and
eﬀec3ve
search
of
data
sets

–  Selec3on
of
appropriate
data
sets
(for
consump3on
or

interlinking)

–  Get
general
sta3s3cs
of
the
data
sets

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Linked
Data
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Describing
RDF
Data
Sets

Describing
RDF
Data
Sets
(2)

•  The
common
language
for
describing
RDF
data
sets
is

VoID
(Vocabulary
of
Interlinked
Data
sets)

•  Deﬁnes
an
RDF
data
set
with
the
predicate

void:Dataset

•  Covers
4
types
of
metadata:

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Linked
Data
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•  General
metadata

•  Structural
metadata

•  Descrip3ons
of
linksets

•  Access
metadata

VoID:
General
Metadata

•  General
metadata
is
used
by
users
to
iden3fy

appropriate
data
sets.

•  Speciﬁes
informa3on
about
descrip3on
of
the
data

set,
contact
person/organiza3on,
the
license
of
the

data
set,
data
subject
and
some
technical
features.

•  VoID
(re)uses
predicates
from
the
Dublin
Core

Metadata1
and
FOAF2
vocabularies.

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1
hjp://dublincore.org/documents/2010/10/11/dcmi-‐terms/

2
hjp://xmlns.com/foaf/spec/

VoID:
General
Metadata
(2)

Predicate
Range
Descrip9on

dcterms:title
Literal
Name
of
the
data
set.

dcterms:description
Literal
Descrip3on
of
the
data
set.

dcterms:source
RDF
resource
Source
from
which
the
data
set
was
derived.

dcterms:creator
RDF
resource
Primarily
responsible
of
crea3ng
the
data
set.

dcterms:date
xsd:date
Time
associated
with
an
event
in
the
life-‐cycle
of
the
resource.

dcterms:created
xsd:date
Date
of
crea3on
of
the
data
set.

dcterms:issued
xsd:date
Date
of
publica3on
of
the
data
set.

dcterms:modified
xsd:date
Date
on
which
the
data
set
was
changed.

foaf:homepage
Literal
Name
of
the
data
set.

dcterms:publisher
RDF
resource
En3ty
responsible
for
making
the
data
set
available.

dcterms:contributor
RDF
resource
En3ty
responsible
for
making
contribu3ons
to
the
data
set.

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Source:

hjp://www.w3.org/TR/void/#metadata

General
Information

Contains
informa3on
about
the
crea3on
of
the
data
set

VoID:
General
Metadata
(3)

Other
Information

•  License
of
the
data
set:
speciﬁes
the
usage
condi3ons
of

the
data.
The
license
can
be
pointed
with
the
property

dcterms:license

•  Category
of
the
data
set:
to
specify
the
topics
or
domains

covered
by
the
data
set,
the
property
dcterms:subject

can
be
used

•  Technical
features:
the
property
void:feature
can
be

used
to
express
technical
proper3es
of
the
data
(e.g.
RDF

serializa3on
formats)

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VoID:
Structural
Metadata

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Data
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•  Provides
high-‐level
informa3on
about
the
internal

structure
of
the
data
set

•  This
metadata
is
useful
when
exploring
or
querying

the
data
set

•  Includes
informa3on
about
resources,
vocabularies

used
in
the
data
set,
sta3s3cs
and
examples
of

resources
in
the
data
set

VoID:
Structural
Metadata
(2)

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Linked
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Information
about
resources

•  Example
resources:
allow
users
to
get
an
impression
of
the

kind
of
resources
included
in
the
data
set.
Examples
can
be

shown
with
the
property
void:exampleResource

•  Pajern
for
resource
URIs:
the
void:uriSpace
property

can
be
used
to
state
that
all
the
en3ty
URIs
in
a
data
set
start

with
a
given
string

:MusicBrainz
a
void:Dataset;

void:exampleResource

<http://musicbrainz.org/artist/b10bbbfc-‐cf9e-‐42e0-‐be17-‐e2c3e1d2600d>
.

:MusicBrainz
a
void:Dataset;

void:uriSpace
"http://musicbrainz.org/"
.

VoID:
Structural
Metadata
(3)

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Vocabularies
used
in
the
data
set

•  The
void:vocabulary
property
iden3ﬁes
the
vocabulary
or

ontology
that
is
used
in
a
data
set

•  Typically,
only
the
most
relevant
vocabularies
are
listed

•  This
property
can
only
be
used
for
en3re
vocabularies.
It

cannot
be
used
to
express
that
a
subset
of
the
vocabulary

occurs
in
the
data
set.

:MusicBrainz
a
void:Dataset;

void:vocabulary
.

VoID:
Structural
Metadata
(4)

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Source:

hjp://www.w3.org/TR/void/#metadata

Statistics
about
a
data
set

Express
numeric
sta3s3cs
about
a
data
set:

Predicate
Range
Descrip9on

void:triples
Number
Total
number
of
triples
contained
in
the
data
set.

void:entities
Number

Total
number
of
en33es
that
are
described
in
the
data
set.

An
en3ty
must
have
a
URI,
and
match
the
void:uriRegexPajern

void:classes
Number
Total
number
of
dis3nct
classes
in
the
data
set.

void:properties
Number
Total
number
of
dis3nct
proper3es
in
the
data
set.

void:distinctSubjects
Number
Total
number
of
dis3nct
subjects
in
the
data
set.

void:distinctObjects
Number
Total
number
of
dis3nct
objects
in
the
data
set.

void:documents
Number
Total
number
of
documents,
in
case
that
the
data
set
is

published
as
a
set
of
individual
documents.

VoID:
Structural
Metadata
(5)

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Partitioned
data
sets

•  The
void:subset
property
provides
descrip3on
of
parts
of
a

data
set

•  Data
sets
can
be
par33oned
based
on
classes
or
proper9es:

•  void:classPartition
contains
only
instances
of
a
par3cular
class

•  void:propertyPartition
contains
only
triples
with
a
par3cular
predicate

:MusicBrainz
a
void:Dataset;

void:subset
:MusicBrainzArtists
.

:MusicBrainz
a
void:Dataset;

void:classPartition
[
void:class
mo:Release
.]
;

void:propertyParition
[
void:property
mo:member
.]
.

VoID:
Describing
Linksets

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•  Linkset:
collec3on
of
RDF
links
between
two

RDF
data
sets

:DS1
:DS2

:LS1
:LS2

Image
based
on
hjp://seman3cweb.org/wiki/File:Void-‐linkset-‐conceptual.png

owl:sameAs

@PREFIX
void:<http://rdfs.org/ns/void#>

@PREFIX
owl:<http://www.w3.org/2002/07/owl#>

:DS1
a
void:Dataset
.

:DS2
a
void:Dataset
.

:DS1
void:subset
:LS1
.

:LS1
a
void:Linkset;

void:linkPredicate

owl:sameAs;

void:target
:DS1,
:DS2
.

VoID:
Describing
Linksets
(2)

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Example

@PREFIX
void:<http://rdfs.org/ns/void#>

@PREFIX
skos:<http://www.w3.org/2002/07/owl#>

:MusicBrainz
a
void:Dataset
.

:DBpedia
a
void:Dataset
.

:MusicBrainz
void:classPartition
:MBArtists
.

:MBArtists
void:class
mo:MusicArtist
.

:MBArtists
a
void:Linkset;

void:linkPredicate

skos:exactMatch;

void:target
:MusicBrainz,
:DBpedia
.

The
access
metadata
describes
the
methods
of

accessing
the
actual
RDF
data
set

*
This
assumes
that
the
default
graph
of
the
SPARQL
endpoint
contains
the
data
set.

VoID
cannot
express
that
a
data
set
is
contained
a
specific
named
graph.
This
can
be

specified
with
SPARQL
1.1.
Service
Descrip3on

VoID:
Access
Metadata

EUCLID
-‐
Providing
Linked
Data
41

Method
Predicate

Descrip9on

URI
look
up
endpoint
void:uriLookupEndpoint

Specifies
the
URI
of
a
service
for
accessing
the
data

set
(different
from
the
SPARQL
protocol)

Root
resource
void:rootResource

URI
of
the
top
concepts
(only
for
data
sets

structured
as
trees)

SPARQL
endpoint
void:sparqlEndpoint
Provides
access
to
the
data
set
via
the
SPARQL

protocol.*

RDF
data
dumps
void:dataDump
Specifies
the
loca3on
of
the
dump
file.
If
the
data

set
is
split
into
mul3ple
files,
then
several
values
of

this
property
are
provided.

CH
5

Providing
Access
to
the

Data
Set

The
data
set
can
be
accessed
via
diﬀerent

mechanisms:

EUCLID
-‐
Providing
Linked
Data
42

RDFa

RDF

dump

SPARQL

endpoint

Dereferencing

HTTP
URIs

Dereferencing
HTTP
URIs

•  Allows
for
easily
exploring
certain
resources

contained
in
the
data
set

• 
What
to
return
for
a
URI?

•  Immediate
descrip9on:
triples
where
the
URI
is
the
subject.

•  Backlinks:
triples
where
the
URI
is
the
object.

•  Related
descrip9ons:
informa3on
of
interest
in
typical
usage
scenarios.

•  Metadata:
informa3on
as
author
and
licensing
informa3on.

•  Syntax:
RDF
descrip3ons
as
RDF/XML
and
human-‐readable
formats.

•  Applica3ons
(e.g.
LD
browsers)
render
the
retrieved

informa3on
so
it
can
be
perceived
by
a
user.

EUCLID
-‐
Providing
Linked
Data
43

Source:

How
to
Publish
Linked
Data
on
The
Web
-‐
Chris
Bizer,
Richard
Cyganiak,
Tom
Heath.

CH
1

Dereferencing
HTTP
URIs
(2)

Example:
Dereferencing

EUCLID
-‐
Providing
Linked
Data
44

RDFa

•  RDFa
=
“RDF
in
ajributes”

•  Extension
to
HTML5
for
embedding
RDF
within

HTML
pages:

–  The
HTML
is
processed
by
the
browser,
the
(human)

consumer
don’t
see
the
RDF
data

–  The
RDF
triples
within
the
page
are
consumed
by
APIs
to

extract
the
(semi-‐)structured
data

•  It
is
considered
as
the
bridge
between
the
Web
of

Data
and
the
Web
of
Documents

•  It
is
a
complete
serializa9on
of
RDF

EUCLID
-‐
Providing
Linked
Data

45

RDFa:
Attributes

A]ribute
role
A]ribute
Descrip9on

Syntax

prefix
List
of
prefix-‐name
IRIs
pairs

vocab
IRI
that
specifies
the
vocabulary
where
the
concept
is
defined

Subject
about
Specifies
the
subject
of
the
rela3onship

Predicate

property
Express
the
rela3onship
between
the
subject
and
the
value

rel
Defines
a
rela3on
between
the
subject
and
a
URL

rev
Express
reverse
rela3onships
between
two
resources

Resource

href
Specifies
an
object
URI
for
the
rel
and
rev
ajributes

resource
Same
as
href
(used
when
href
is
not
present)

src
Specifies
the
subject
of
a
rela3onship

Literal

datatype
Express
the
datatype
of
the
object
of
the
property
ajribute

content
Supply
machine-‐readable
content
for
a
literal

xml:lang,
lang
Specifies
the
language
of
the
literal

Macro
typeof
Indicate
the
RDF
type(s)
to
associate
with
a
subject

inlist
An
object
is
added
to
the
list
of
a
predicate.

EUCLID
-‐
Providing
Linked
Data

46

RDFa:
Example

Extracting
RDF
from
HTML

EUCLID
-‐
Providing
Linked
Data

47

<div
class="ar3stheader"

about="hjp://musicbrainz.org/ar3st/b10bbbfc-‐cf9e-‐42e0-‐be17-‐e2c3e1d2600d#_"

typeof="hjp://purl.org./ontology/mo/MusicGroup">

…

</div>

<hjp://musicbrainz.org/ar3st/b10bbbfc-‐cf9e-‐42e0-‐be17-‐e2c3e1d2600d#_>

HTML
(+RDFa):

RDF:

RDFa:
Example

Extracting
RDF
from
HTML

EUCLID
-‐
Providing
Linked
Data

48

<div
class="ar3stheader"



…

</div>


<hjp://www.w3.org/1999/02/22-‐rdf-‐syntax-‐ns#type>

HTML
(+RDFa):

RDF:

RDFa:
Example

Extracting
RDF
from
HTML

EUCLID
-‐
Providing
Linked
Data

49

<div
class="ar3stheader"



…

</div>


<hjp://www.w3.org/1999/02/22-‐rdf-‐syntax-‐ns#type>

<hjp://purl.org./ontology/mo/MusicGroup>.

HTML
(+RDFa):

RDF:

RDFa:
Example
(2)

Extracting
RDF
from
MusicBrainz.org

EUCLID
-‐
Providing
Linked
Data

50

hjp://musicbrainz.org/ar3st/b10bbbfc-‐cf9e-‐42e0-‐be17-‐e2c3e1d2600d

RDFa:
Example
(2)

Extracting
RDF
from
MusicBrainz.org

EUCLID
-‐
Providing
Linked
Data

51

Source:
hjp://www.w3.org/2007/08/pyRdfa/

RDFa:
Example
(2)

Extracting
RDF
from
MusicBrainz.org

EUCLID
-‐
Providing
Linked
Data

52

hjp://www.w3.org/2007/08/pyRdfa/extract?uri=hjp%3A%2F%2Fmusicbrainz.org
%2Far3st%2Fb10bbbfc-‐cf9e-‐42e0-‐be17-‐e2c3e1d2600d&format=nt

Watch
the
EUCLID
screencast:
http://vimeo.com/euclidproject

RDF
Dump

•  An
RDF
dump
refers
to
a
ﬁle
which
contains
(part
of)

a
data
set
speciﬁed
in
an
RDF
format
(RDF/XML,
N-‐
Triples,
N-‐Quads)

•  The
data
set
can
be
split
into
several
RDF
dumps

•  A
list
of
available
data
sets
available
as
RDF
dumps

can
be
found
at:

–  hjp://www.w3.org/wiki/DataSetRDFDumps

EUCLID
-‐
Providing
Linked
Data
53

SPARQL
Endpoint

•  The
SPARQL
endpoint
refers
to
the
URI
of
the

listener
of
the
SPARQL
protocol
service,
which

handles
requests
for
SPARQL
protocol
opera3ons

•  The
user
submits
SPARQL
queries
to
the
SPARQL

endpoint
in
order
to
retrieve
only
a
desired
subset
of

the
RDF
data
set

•  List
of
available
SPARQL
endpoints:

•  hjp://www.w3.org/wiki/SparqlEndpoints

•  hjp://labs.mondeca.com/sparqlEndpointsStatus/

EUCLID
-‐
Providing
Linked
Data
54

CH
2

Using
Linked
Data
Catalogs

•  Data
catalogs,
markets
or
repositories
are
pla{orms

dedicated
to
provide
access
to
a
wide
range
of
data

sets
from
different
domains

•  Allow
data
consumers
to
easily
find
and
use
the
data

•  Usually
the
catalogs
offer
relevant
metadata
about

the
crea3on
of
the
data
set

EUCLID
-‐
Providing
Linked
Data
55

Using
Linked
Data
Catalogs
(2)

How
to
publish
an
RDF
data
set
into
a
catalog?

EUCLID
-‐
Providing
Linked
Data
56

Create
your
own
data

catalog

Recommended
for
big

organiza3ons/ins3tu3ons

aiming
at
providing
a
large

number
of
data
sets

Use
a
data
management

system,
for
example:

Upload
your
data
set

into
an
exis3ng
catalog

Allows
data
consumers
to

easily
ﬁnd
new
data
sets

Common
LD
catalogs
are:

-‐

-‐
The
Linking
Open
Data
Cloud

Validating
Data
Sets

There
are
diﬀerent
ways
to
validate
the
published
RDF

data
set:

EUCLID
-‐
Providing
Linked
Data
57

General

validators

Parsing
&

Syntax

•  Vapour
-‐
Performs
two
types
of
tests:
without
content

nego3a3on
and
reques3ng
RDF/XML
content

hjp://validator.linkeddata.org/vapour

•  URI
Debugger
-‐
Retreieves
the
HTTP
responses
of
accessing
a
URI

hjp://linkeddata.informa3k.hu-‐berlin.de/uridbg/

•  RDF
Triple-‐Checker
–
Dereferences
namespaces
associated
with

the
resources
used
in
the
document

hjp://graphite.ecs.soton.ac.uk/checker/

•  W3C
RDF/XML
Valida9on
Service
–
Evaluates
the
syntax
of
RDF/
XML
documents
and
displays
the
RDF
triples
in
it

hjp://validator.linkeddata.org/vapour

•  W3C
Markup
Valida9on
Service
–
Checks
syntac3c
correctness

for
web
documents
with
RDFa
markup

hjp://validator.w3.org/

•  RDF:ALERTS
–
Validates
syntax,
undeﬁned
resources,
datatype

and
other
types
of
errors

hjp://swse.deri.org/RDFAlerts/

Accessibility

Validating
Data
Sets
(2)

Example:
Validating
URIs
with
Vapour

EUCLID
-‐
Providing
Linked
Data
58

Source:
hjp://idi.fundacionc3c.org/vapour

Validating
Data
Sets
(3)

Example:
Validating
URIs
with
Vapour

EUCLID
-‐
Providing
Linked
Data
59

Source:

Validating
Data
Sets
(4)

Example:
Validating
URIs
with

Vapour

EUCLID
-‐
Providing
Linked
Data
60

Source:

Example:
Validating
URIs
with
Vapour

hjp://dbpedia.org/page/The_Beatles

hjp://dbpedia.org/data/The_Beatles.xml

HTML
content

RDF
document

PROVIDING
LINKED
DATA:

CHECKLIST

EUCLID
-‐
Providing
Linked
Data
61

Providing
Linked
Data:

Checklist
(1)

Creating
Linked
Data

o All
the
relevant
en33es/concepts
were

eﬀec3vely
extracted
from
the
raw
data
?

o Are
all
the
created
URIs
dereferenceable?

o Are
you
reusing
terms
from
widely
accepted

vocabularies?

EUCLID
-‐
Providing
Linked
Data
62

Providing
Linked
Data:

Checklist
(2)

Interlinking
Linked
Data

o Is
the
data
set
linked
to
other
RDF
data
sets?

o Are
the
created
vocabulary
terms
linked
to

other
vocabularies?

EUCLID
-‐
Providing
Linked
Data
63

Providing
Linked
Data:

Checklist
(3)

Publishing
Linked
Data

o Do
you
provide
data
set
metadata?

o Do
you
provide
informa3on
about
licensing?

o Do
you
provide
addi3onal
access
methods?

o Is
the
data
set
available
in
LD
catalogs?

o Did
the
data
set
pass
the
valida3on
tests?

EUCLID
-‐
Providing
Linked
Data
64

Summary

EUCLID
-‐
Providing
Linked
Data
65

•  The
Linked
Data
lifecycle:

•  3
core
tasks:
crea3ng,
interlinking
and
publishing

•  Crea3on
of
Linked
Data:

•  Extrac3ng
relevant
data,
using
URIs
to
name
en33es
and
selec3ng

vocabularies
and
expressing
the
data
using
the
RDF
data
model

•  Interlinking
Linked
Data:

•  Challenges
of
link
discovery,
using
Silk
to
create
links
between
two

data
sets
and
using
SKOS
links

•  Publishing
Linked
Data:

•  Crea3on
of
data
set
metadata;
publishing
the
data
set
via
RDF

dumps,
SPARQL
endpoints
or
RDFa;
using
RDFa
and
schema.org
to

enrich
search
results,
and
uploading
the
data
set
to
a
LD
catalog

In
this
chapter
we
studied:

The
Web
&
Linked
Data

•  Linked
Data
catalogs

•  Applica9ons

CKAN

•  CKAN
is
an
open
source
pla{orm
for
developing
data

set
catalogs

•  Implement
useful
tools
for
data
publishers
to

support:

•  Data
harves3ng

•  Crea3on
of
metadata

•  Access
mechanisms
to
the
data
set

•  Upda3ng
the
data
set

•  Monitoring
the
access
to
the
data
set

EUCLID
-‐
Providing
Linked
Data
67

CKAN
(2)

EUCLID
-‐
Providing
Linked
Data
68

Source:
hjp://ckan.org

CKAN
(3)

EUCLID
-‐
Providing
Linked
Data
69

Source:
hjp://ckan.org

•  The
Data
Hub
is
a
community-‐run
data
catalog
which

contains
more
than
5,000
data
sets1

•  “(…)
is
an
openly
editable
open
data
catalogue,
in
the

style
of
Wikipedia”.2

•  It
is
implemented
on
top
of
the
CKAN
pla{orm

•  Allows
the
crea3on
of
groups:

–  The
Linking
Open
Data
Cloud
group
exclusively
contains

Linked
Data
sets

EUCLID
-‐
Providing
Linked
Data
70

1
According
to
the
informa3on
presented
in
the
portal
on
March
2013

2
Source:
hjp://datahub.io/about

The
Data
Hub

EUCLID
-‐
Providing
Linked
Data
71

Source:
hjp://datahub.io/

The
Data
Hub
(2)

The
Data
Hub
(3)

EUCLID
-‐
Providing
Linked
Data
72

Source:
hjp://datahub.io/

The
Linking
Open
Data
Cloud

EUCLID
-‐
Providing
Linked
Data
73

September
2011

Source:
Linking
Open
Data
cloud
diagram,
by
Richard
Cyganiak
and
Anja
Jentzsch

The
Linking
Open
Data
Cloud

How
to
publish
an
RDF
data
set
in
this
cloud?

1.  The
data
set
must
follow
the
Linked
Data
principles

2.  The
data
set
must
contain
at
least
1,000
RDF
triples

3.  The
data
set
must
contain
at
least
50
RDF
links
to
a

data
set
that
is
already
in
the
diagram

4.  Access
to
the
data
set
must
be
provided

Once
these
criteria
are
met,
the
data
publisher
must
add

the
data
set
to
the
Data
Hub
catalog,
and
contact
the

administrators
of
the
Linking
Open
Data
Cloud
group

EUCLID
-‐
Providing
Linked
Data
74

Source:
hjp://lod-‐cloud.net/

Linked
Data
&
Search
Engines

EUCLID
-‐
Providing
Linked
Data
75

•  Search
engines
collect
informa3on
about
web

resources
in
order
to
produce
richer
search
results

by
improving
the
display
of
the
results

•  This
is
only
possible
if
the
search
engines
are
able
to

understand
the
content
within
the
web
pages

•  The
HTML
pages
must
be
annotated
with
machine-‐
readable
content
to
describe
their
content:

Mark
up
format
Vocabulary

RDFa
for
marking
up
data

EUCLID
-‐
Providing
Linked
Data
76

•  RDFa
is
used
to
provide
(semi-‐)structured
Linked

Data
embedded
in
web
content

•  Examples:

– Some
search
engines
use
RDFa,
e.g.,
Google,

Yahoo!
and
Bing

– Facebook’s
Open
Graph
is
based
on
RDFa

Google
Rich
Snippets

EUCLID
-‐
Providing
Linked
Data
77

•  Embedding
seman3cs
via
RDFa
(or
microformats/
microdata)
enhances
search
results:

Google
Rich
Snippets
(2)

EUCLID
-‐
Providing
Linked
Data
78

Schema.org

EUCLID
-‐
Providing
Linked
Data
79

•  Collec3on
of
schemas/vocabularies
to
markup
the

HTML
pages

•  It
is
recognized
by
Bing,
Google,
Yahoo!
and
Yandex

•  Covers
a
wide
range
of
knowledge
domains

•  It
also
oﬀers
an
extension
mechanism
in
case
the

publisher
is
interested
in
adding
new
concepts
to
the

vocabularies

Schema.org
(2)

EUCLID
-‐
Providing
Linked
Data
80

The
vocabularies
cover
the
following
topics:

Source:
hjp://schema.org/docs/schemas.html

“The
world
is
too
rich,

complex
and
interes.ng
for

a
single
schema
to
describe

fully
on
its
own.
With

schema.org
we
aim
to
ﬁnd
a

balance,
by
providing
a
core

schema
that
covers
lots
of

situa.ons,
alongside

extension
mechanisms
for

extra
detail.”

(Dan
Brickley,
schema.org)

EUCLID
-‐
Providing
Linked
Data
81

Integrates(/aligns)
exis3ng
vocabularies
where

appropriate,
e.g.
rNews

Source:
hjp://schema.org/Ar3cle

Schema.org
(3)

Google
Knowledge
Graph

EUCLID
-‐
Providing
Linked
Data
82

•  The
user
is
able
to
ﬁnd

answer
to
their
queries

without
browsing
pages

•  Provides
detailed

informa3on

Google
Knowledge
Graph
(2)

EUCLID
-‐
Providing
Linked
Data
83

•  Google
Search
results

include
structured
data

from
Freebase

•  Might
disambiguate

search
terms

Freebase

EUCLID
-‐
Providing
Linked
Data
84

•  Knowledge
base
of

structured
data

•  Data
is
stored
as
a

graph

•  Describes
data
from

diﬀerent
domains

Bing
Snapshot

EUCLID
-‐
Providing
Linked
Data
85

•  Provides
structured
data
related
to
the
search
term

•  Includes
a
signiﬁcant
number
of
en33es
from
more

domains

•  Connects
data
from
LinkedIn

•  Is
is
powered
by
the
graph
engine
Trinity.RDF

Bing
Snapshot
(2)

EUCLID
-‐
Providing
Linked
Data
86

Open
Graph
Protocol

EUCLID
-‐
Providing
Linked
Data
87

•  It
was
originally
created
by
Facebook

•  Allows
describing
web
content
as
graph
objects,

establishing
connec3ons
between
people
and

objects

•  The
descrip3ons
are
embedded
in
the
web
page
as

RDFa
data

•  Supports
descrip3on
of
several
domains:
basic

metadata,
music,
video,
ar3cles,
books,
websites
and

user
proﬁles

Source:
hjp://ogp.me/

Open
Graph
Protocol
(2)

EUCLID
-‐
Providing
Linked
Data
88

Source:
hjp://ogp.me/

Who
is
using
Open
Graph
protocol?

Source:
hjp://ogp.me/

Facebook

Google

Mixi

Consumers
Publishers

IMDb

Microso•

NHL

Posterous

Rojen
Tomatoes

TIME

Open
Graph
Protocol
(3)

EUCLID
-‐
Providing
Linked
Data
89

•  Facebook
expands
vocabulary
of
rela3onships
beyond

“friendship”
and
“like”

more
ac9ons!

Source:
hjps://developers.facebook.com/docs/opengraph/

Open
Graph
Protocol
&

Facebook

EUCLID
-‐
Providing
Linked
Data
90

List
of
domains
and
ac9ons

Source:
hjps://developers.facebook.com/docs/opengraph/

•  Listen

•  Create
a
playlist

•  Watch

•  Rate

•  Wants
to
watch

•  Rate

•  Read

•  Quote

•  Wants
to
read

•  Achieve

•  High
score

•  Bike

•  Run

•  Walk

•  Like

•  Recommend

•  Follow

General

Music

Movies

&
TV

Games

Fitness

Book

How
can
we
exploit
these
links
and
rela3onships?

Facebook
Graph
Search

EUCLID
-‐
Providing
Linked
Data
91

•  focuse
on
people
and
their
interests,
exploi3ng

how
everything
is
related
to
each
other

•  Queries
are
speciﬁed
using
natural
language

•  Takes
advantage
of
context
and
suggest
possible

queries

•  Allows
for
building
more
complex
(expressive)

queries
that
are
not
possible
with
normal
search:

–  For
example,
“music
liked
by
me
and
friends
who
live
in

my
city”

Facebook
Graph
Search
(2)

EUCLID
-‐
Providing
Linked
Data
92

Context
(informa3on
from
proﬁle):

Graph
search
sugges9ons:

Facebook
Graph
Search
(3)

EUCLID
-‐
Providing
Linked
Data
93

Results

Facebook
Graph
Search
(4)

EUCLID
-‐
Providing
Linked
Data
94

Observations

•  Allows
for
conjunc3ve
queries
(applying
ﬁlter
over
intermediate

results
=
“apply
operator”)

•  Disjunc9ve
queries
are
not
supported:

–  For
example:
“My
friends
who
like
Seman3cWeb.com
OR
ReadWrite”

•  Post
search
is
not
supported

–  It
is
not
possible
to
search
in
post
content
submijed
to
the
3meline

•  User
privacy
segngs
aﬀect
the
results

Tools
for
providing
Linked
Data

•  Extrac9ng
data
from
spreadsheets:
OpenReﬁne

•  Extrac9ng
data
from
RDBMS:
R2RML

•  Extrac9ng
data
from
text:
Zemanta,
OpenCalais,
GATE

•  Interlinking
data
sets:
Silk

EXTRACTING
DATA
FROM

SPREADSHEETS
WITH
OPENREFINE

EUCLID
-‐
Providing
Linked
Data
96

Integrate
Chart
Data

•  Task:
Integrate
latest
chart

informa3on
into
your
RDF

database.

•  Data
may
be
available
in
non-‐
RDF
formats:

–  Plain
text

–  CSV,
TSV,
separator-‐based

ﬁles

–  HTML
tables

–  Spreadsheets

(OpenDocument,
Excel,
…)

–  XML

–  JSON

–  …

97

LD
Data
set
Access

Integrated

Data
Set

Interlinking
Cleansing

Vocabulary

Mapping

SPARQL

Endpoint

Publishing

CSV/

TSV

HTML
Spreadsheets
JSON

Data
acquisi3on

EUCLID
-‐
Providing
Linked
Data

Example
Data

The Beatles, 250 million
Elvis Presley, 203.3 million
Michael Jackson, 157.4 million
Madonna, 160.1 million
Led Zeppelin, 135.5 million
Queen, 90.5 million

98

hjp://en.wikipedia.org/wiki/

List_of_best-‐selling_music_ar3sts

Ar3st

Country
of

origin

Period

ac3ve

Release-‐year

of
first

charted

record

Total
cer3fied
units

(from
available
markets)[Notes]

The
Beatles

United

Kingdom

1960–
1970[4]

1962[4]

Total
available
cer9fied
units:

250
million[show]

Elvis
Presley

United

States

1954–
1977[28]

1954[28]

Total
available
cer9fied
units:

203.3
million[show]

Michael

Jackson[Note
2]

United

States

1964–
2009[32]

1971[32]

Total
available
cer9fied
units:

157.4
million[show]

Madonna

United

States

1979–
present[44]

1982[44]

Total
available
cer9fied
units:

160.1
million[show]

Led
Zeppelin

United

Kingdom

1968–
1980[50]

1969[50]

Total
available
cer9fied
units:

135.5
million[show]

Queen

United

Kingdom

1971–
present[53]

1973[53]

Total
available
cer9fied
units:

90.5
million[show]

{
"artist": {
"class": "artist",
"name": "The Beatles"
},
"rank": 1,
"value": 250 million
},
…
CSV

JSON

HTML
tables

EUCLID
-‐
Providing
Linked
Data

OpenReﬁne

•  transforms
and
cleans
messy

input
data
sets.

•  is
an
open-‐source
successor
of

Google
Reﬁne.

•  allows
for
en3ty
reconcilia3on

against
SPARQL
endpoints
or

RDF
data.

•  is
extended
with
plugins
that

enhance
its
func3onality,
e.g.

for
RDF
support.

99
EUCLID
-‐
Providing
Linked
Data

Quick
Facts

Use
of
OpenReﬁne

100

1.  Messy
input
data
is

imported,

transformed

into
a
table
represen-‐
ta3on
and
cleaned.

3.  Deﬁne
the
structure
of

the
RDF
output.

4.  The
data
is
exported

into
some
RDF
syntax.

2.  En3ty
reconcilia3on
is

applied
to
allow
for

interlinking
with

exis3ng
data
sets.

The Beatles, 250 million
Elvis Presley, 203.3 million
Michael Jackson, 157.4 million
Madonna, 160.1 million
Led Zeppelin, 135.5 million
Queen, 90.5 million

CSV

musicbrainz:b10bbbfc-cf9e-42e0-be17-e2c3e1d2600d :totalSales "25000000000"^^xsd:int .

musicbrainz:01809552-4f87-45b0-afff-2c6f0730a3be :totalSales "2.033E10"^^xsd:int .

musicbrainz:f27ec8db-af05-4f36-916e-3d57f91ecf5e :totalSales "1.574E10"^^xsd:int .

musicbrainz:79239441-bfd5-4981-a70c-55c3f15c1287 :totalSales "1.601E10"^^xsd:int .

musicbrainz:678d88b2-87b0-403b-b63d-5da7465aecc3 :totalSales "1.355E10"^^xsd:int .

musicbrainz:0383dadf-2a4e-4d10-a46a-e9e041da8eb3 :totalSales "9.05E9"^^xsd:int .
RDF

EUCLID
-‐
Providing
Linked
Data

Typical
steps:

•  Group
and
explore
data

items

•  Dele3ng
columns
or
rows

based
on
ﬁlter
condi3on

•  Split
columns
into
several

columns
based
on

condi3on

•  Modify
messy
data
items

with
GREL,
a
powerful

expression
language

•  Replay
steps
from
a

previous
Reﬁne
project

101
EUCLID
-‐
Providing
Linked
Data

Data
Transformation

How
to
Generate
RDF?

•  Addi3onal
problem:
data
needs
to
be
interlinked

with
exis3ng
MusicBrainz
data

•  This
is
the
point
where
plugins
come
into
play:

–  RDF
Reﬁne:
developed
by
DERI

–  An
extension
of
OpenReﬁne
to
support
RDF

102

?

RDF

EUCLID
-‐
Providing
Linked
Data

Core
Capabilities

•  Interlinking
of
data
by
en3ty
reconcilia3on

– Against
SPARQL
endpoints,
RDF
dumps

– Discovery
of
relevant
RDF
data
sets

•  RDF
export
with
the
help
of
RDF
skeletons

– Deﬁne
the
vocabulary
and
graph
structure
of
the

RDF
serializa3on

– In
Turtle,
RDF/XML

103
EUCLID
-‐
Providing
Linked
Data

Typical
steps:

•  Deﬁne
a
reconcilia3on
service

•  Select
speciﬁc
types
to
reconcile
against

•  Start
reconciling
a
column
against
the

service

104
EUCLID
-‐
Providing
Linked
Data

Entity
Reconciliation

Deﬁne
RDF
Skeletons

•  An
RDF
skeleton
deﬁnes
the
structure
of
the

RDF
triples
that
are
exported

EUCLID
-‐
Providing
Linked
Data
105

RDF
Skeletons

03.09.13
106
106
EUCLID
-‐
Providing
Linked
Data

EXTRACTING
DATA
FROM

RDBMS
WITH
R2RML

EUCLID
-‐
Providing
Linked
Data
107

W3C
RDB2RDF

•  Task:
Integrate
data
from

rela3onal
DBMS
with
Linked

Data

•  Approach:
map
from

rela3onal
schema
to
seman3c

vocabulary
with
R2RML

•  Publishing:
two
alterna3ves
–

–  Translate
SPARQL
into

SQL
on
the
ﬂy

–  Batch
transform
data
into

RDF,
index
and
provide

SPARQL
access
in
a

triplestore

108

LD
Data
set
Access

Integrated

Data
in

Triplestore

Interlinking
Cleansing

Vocabulary

Mapping

SPARQL

Endpoint

Publishing

Data
acquisi3on

EUCLID
-‐
Providing
Linked
Data

R2RML

Engine

Rela3onal

DBMS

W3C
RDB2RDF

•  The
W3C
made,
last
year,
two
recommenda3ons
for

mapping
between
rela3onal
databases
and
RDF:

–  Direct
mapping
directly
exposes
data
as
RDF

•  Not
allowance
for
vocabulary

mapping

•  No
allowance
for
interlinking
(unless
URIs
used
in
rela3onal
data)

•  Not
appropriate
for
this
topic

– R2RML,
the
RDB
to
RDF
mapping
language

•  Allows
vocabulary
mapping
(subject,
predicate
and

object
maps
with
class
op3ons)

•  Allows
interlinking
–
URIs
can
be
constructed

•  Means
to
provide
MusicBrainz
RDF/SPARQL
itself

EUCLID
-‐
Providing
Linked
Data
109

hjp://www.w3.org/2001/sw/rdb2rdf/

MusicBrainz
Next
Gen
Schema

EUCLID
-‐
Providing
Linked
Data
110

•  Ar9st

As
pre-‐NGS,
but

further
ajributes

•  Ar9st
Credit

Allows
joint
credit

•  Release
Group

Cf.
‘album’

versus:

•  Release

•  Medium

•  Track

•  Track
List

•  Work

•  Recording

Source:
hjps://wiki.musicbrainz.org/Next_Genera3on_Schema

Music
Ontology

•  OWL
ontology
with
following
core
concepts

(classes)
and
rela3onships
(proper3es):

EUCLID
-‐
Providing
Linked
Data
111

Source:
hjp://musicontology.com

R2RML
Class
Mapping

•  Mapping
tables
to
classes
is
‘easy’:

lb:Artist
a
rr:TriplesMap
;

rr:logicalTable
[rr:tableName
"artist"]
;

rr:subjectMap

[rr:class
mo:MusicArtist
;

rr:template

"http://musicbrainz.org/artist/{gid}#_"]
;

rr:predicateObjectMap

[rr:predicate
mo:musicbrainz_guid
;

rr:objectMap
[rr:column
"gid"
;

rr:datatype
xsd:string]]
.

EUCLID
-‐
Providing
Linked
Data
112

R2RML
Property
Mapping

•  Mapping
columns
to
proper3es
can
be
easy:

lb:artist_name
a
rr:TriplesMap
;

rr:logicalTable
[rr:sqlQuery

"""SELECT
artist.gid,
artist_name.name

FROM
artist

INNER
JOIN
artist_name
ON
artist.name
=

artist_name.id"""]
;

rr:subjectMap
lb:sm_artist
;


[rr:predicate
foaf:name
;

rr:objectMap
[rr:column
"name"]]
.

EUCLID
-‐
Providing
Linked
Data
113

NGS
Advanced
Relations

EUCLID
-‐
Providing
Linked
Data
114

•  Major
en33es
(Ar3st,
Release
Group,
Track,
etc.)
plus

URL
are
paired

(l_ar3st_ar3st)

•  Each
pairing

of
instances

refers
to
a
Link

•  Links
have
types

(cf.
RDF
proper3es)

and
ajributes

Source:
hjp://wiki.musicbrainz.org/Advanced_Rela3onship

R2RML
Advanced
Mapping

•  Mapping
advanced
rela3onships
(SQL
joins):

lb:artist_member
a
rr:TriplesMap
;

rr:logicalTable
[rr:sqlQuery

"""SELECT
a1.gid,
a2.gid
AS
band

FROM
artist
a1

INNER
JOIN
l_artist_artist
ON
a1.id
=

l_artist_artist.entity0

INNER
JOIN
link
ON
l_artist_artist.link
=
link.id

INNER
JOIN
link_type
ON
link_type
=
link_type.id

INNER
JOIN
artist
a2
on
l_artist_artist.entity1
=
a2.id

WHERE
link_type.gid='5be4c609-‐9afa-‐4ea0-‐910b-‐12ffb71e3821'

AND
link.ended=FALSE"""]
;

rr:subjectMap
lb:sm_artist
;


[rr:predicate
mo:member_of
;

rr:objectMap
[rr:template
"http://musicbrainz.org/artist/
{band}#_"
;

rr:termType
rr:IRI]]
.

EUCLID
-‐
Providing
Linked
Data
115

EXTRACTING
DATA
FROM
TEXT

EUCLID
-‐
Providing
Linked
Data
116

OpenCalais

•  Not
easily
customised/extended

•  Domain-‐speciﬁc
coverage
varies

EUCLID
-‐
Providing
Linked
Data
117

Source:
hjp://viewer.opencalais.com/

DBpedia
Spotlight

•  Not
easily
customised/extended

•  Is
currently
only
available
for
English

EUCLID
-‐
Providing
Linked
Data
118

Source:
hjp://dbpedia-‐spotlight.github.com/demo/

hjp://dbpedia.org/page/Slowcore

hjp://dbpedia.org/page/Dorothy_Parker

Zemanta

EUCLID
-‐
Providing
Linked
Data
119

Source:
hjp://www.zemanta.com/demo/

•  Common
problem
with
general
purpose,
open-‐domain

seman3c

annota3on

tools

•  Best
results

require

bespoke

customisa3on

•  General
Architecture
for
Text
Engineering

•  Free
open-‐source
(LGPL)

framework
and
development
environment

•  Started
1996,
large
developer
community

•  Used
worldwide
by
many
organisa3ons
to

build
bespoke
solu3ons;
e.g.
Press
Associa3on

and
the
Na3onal
Archive

•  Informa3on
Extrac3on
in
many
languages

GATE

EUCLID
-‐
Providing
Linked
Data
120

hjp://www.gate.ac.uk/

•  Increases
recall
over
DBpedia
by
deriving
new

lexicalisa3ons
for
URIs
from
link
anchor
texts,

disambigua3on
pages,
and
redirect
pages

GATE
Example
-‐
LODIE

EUCLID
-‐
Providing
Linked
Data
121

Precision
and
Recall

•  Generic
services
typically
very
low
recall

•  Combina3on
is
one
solu3on

•  Other
solu3on
is
custom
extrac3on

122

PER LOC ORG TOTAL
DB
Spotlight 0.97
/
0.40 0.82
/
0.46 0.86
/
0.31 0.85
/
0.39
Zemanta 0.96
/
0.84 0.89
/
0.62 0.82
/
0.57 0.90
/
0.68
LODIE 0.81
/
0.82 0.73
/
0.76 0.56
/
0.59 0.71
/
0.74
Zemanta
∩
LODIE 1.00
/
0.74 0.95
/
0.45 0.97
/
0.42 0.97
/
0.54
Zemanta
U
LODIE 0.94
/
0.93 0.77
/
0.76 0.72
/
0.71 0.82
/
0.81
EUCLID
-‐
Providing
Linked
Data

Custom
GATE
Gazetteer

•  Retrieve
MusicBrainz

en3ty/label/class

with
SPARQL
query

123
EUCLID
-‐
Providing
Linked
Data

GATECloud

•  Custom
(e.g.
based
around
custom
gazejeer)

GATE
pipelines
can
be
executed
on
the
cloud:

124
EUCLID
-‐
Providing
Linked
Data

INTERLINKING
DATA
SETS
WITH

SILK

EUCLID
-‐
Providing
Linked
Data
125

Interlinking
with
Silk

•  Task:
Create
links
between

the
data
set
and
external

Linked
Data
sources.

•  Approach:
Crea3on
of

speciﬁed
links
by
querying

the
target
data
sets

•  Alterna9ves:

–  Manual
crea3on
of

linkage
rules
by
the
user

–  Automa3c
learning

linkage
rules
by

submi…ng
predeﬁned

SPARQL
queries

126

LD
Data
set
Access

Integrated

Data
Set

Interlinking
Cleansing

Vocabulary

Mapping

SPARQL

Endpoint

Publishing

CSV/

TSV

HTML
Spreadsheets
JSON

Data
acquisi3on

EUCLID
-‐
Providing
Linked
Data

Link
Discovery
with
Silk

•  Open
source
tool
for
discovering
RDF
links
between

data
items
within
diﬀerent
Linked
Data
sources

•  It
is
based
on
the
Silk
Link
Speciﬁca3on
Language

(Silk-‐LSL)
for
expressing
linkage
rules

•  It
accesses
the
target
RDF
data
sets
via
SPARQL

endpoints
to
generate
RDF
links

EUCLID
-‐
Providing
Linked
Data
127

Source:
Robert
Isele.
“LOD2
Webinar
Series:Silk”

Silk
Variants

•  Silk
Single
Machine

•  Generates
RDF
links
on
a
single
machine

•  Data
sets
can
reside
either
locally
or
in
remote
machines

•  Provides
mul3threading
and
caching

•  Silk
MapReduce

•  Uses
a
cluster
composed
of
mul3ple
machines

•  Based
on
Hadoop
and
designed
to
scale
to
big
data
sets

•  Silk
Server

•  Used
within
applica3ons
that
consume
Linked
Data
from
the
Web

while
keeping
track
of
known
en33es

•  Provides
an
HTTP
API
for
matching
en33es
from
an
incoming

stream

EUCLID
-‐
Providing
Linked
Data
128

Source:
hjp://wifo5-‐03.informa3k.uni-‐mannheim.de/bizer/silk/

Source:
Silk
workflow
is
par3ally
based
on
“LOD2
Webinar
Series:
Silk
-‐(Simplified)

Linking
Workflow”
by
Rober
Isele.

Silk
Workflow

EUCLID
-‐
Providing
Linked
Data
129

Select
LD

data
sets

•  Iden3fy

suitable
data

sets
in
LD

catalogs*

•  Select
the
two

data
sets
to

link

Specify
LD

data
sets

•  Specify
the

access
method

to
the
data
set

(RDF
dump,

SPARQL

endpoint)*

•  Specify
the

en3ty
types
to

be
linked

Write

linkage
rule

•  Specifies
how

to
compare

the
resources

•  Use
Silk-‐LSL

•  The
rules
can

also
be
learnt

Generate

RDF
links

•  Output
links

can
be
stored

in
a
file
or
a

triple
store

•  Can
discover

SKOS
links

Silk
framework

*
See
sec3on
“Publishing
Linked
Data”

Linkage
Rule
Components

•  Linkage
rules
deﬁne
the
condi3ons
to
create
the
links

between
the
data
sets.
These
rules
are
composed
of:

EUCLID
-‐
Providing
Linked
Data
130

Source:
hjp://wifo5-‐03.informa3k.uni-‐mannheim.de/bizer/silk/

RDF
Paths

•  Describe
the
elements
to
be

compared

•  Example:
?a/rdfs:label

Transforma9ons

•  Apply
transforma3ons
to
the

result
set
of
an
RDF
path

•  Examples:
LowerCase,

Concatenate,
Replace,
…

Comparators

•  Compute
the
similarity
of
two

inputs

•  Examples:
String
similarity

metrics,
Date
similarity,
…

Aggrega9ons

•  Compute
an
aggregated
value

from
mul3ple
comparators

•  Examples:
Min,
Max,
Avg,
various

means,
Euclidian
distance
…

1
2

3
4

Silk
Workbench

•  Web
applica3on
built
on
top
of
Silk,
which
allows
the

crea3on
of
projects
to
manage
the
crea3on
of
links

between
RDF
data
sets

•  The
data
sets
can
be
stored
locally
or
accessed

remotely
by
specifying
the
SPARQL
endpoint

•  The
user
is
able
to
create
customized
linking
tasks:

–  The
tool
oﬀers
a
graphical
editor
to
create
linkage
rules
by

combining
the
linkage
rules
components
via
drag
&
drop

elements

–  Includes
support
for
(automa3c)
learning
linkage
rules

EUCLID
-‐
Providing
Linked
Data
131

Project
configuration

Silk
Workbench
(2)

EUCLID
-‐
Providing
Linked
Data
132

1

2

3

4

1.  Project:
name
and
components
(data

sources,

linking
tasks
and
output
tasks)

2.  Data
sources:
specifica3on
of
the
data

sets
to
be
interlinked

3.  Linking
task:
specifica3on
of
the
linkage

rules
and
type
of
links
to
be
created

4.  Output
task:
mechanism
to
store
the

results
from
the
lnking
process

2

Editing
a
linking
task

Silk
Workbench
(3)

EUCLID
-‐
Providing
Linked
Data
133

1

4

2

3

1.  Linkage
rule
components

2.  Graphical
editor:
the
items
from
(1)
are
dragged
&

dropped
in
this
area,
and
connected
to
compose
the

linkage
rules

3.  Generate
links:
based
on
the
deﬁned
linkage
rules
in
(2),

the
data
sets
are
accessed
to
discover
possible
links

4.  Learn:
automa3c
learning
of
linkage
rules

Adding
a
linkage
rule

Silk
Workbench
(4)

EUCLID
-‐
Providing
Linked
Data
134

The
previous
linkage
rule
states:

1.  Retrieve
the
foaf:name
values
from
MusicBrainz
and

the
rdfs:label
from
DBpedia

2.  Apply
lower
case
transforma3on
to
the
output
of
(1)

3.  Compare
the
output
from
(2)
using
the
metric

“Levenshtein
distance”.
If
this
distance
is
greater
than

0.90,
then
create
a
link.

1
2

3

Generate
Links

Silk
Workbench
(5)

EUCLID
-‐
Providing
Linked
Data
135

Learn
Rules

Silk
Workbench
(6)

EUCLID
-‐
Providing
Linked
Data
136

For
exercises,
quiz
and
further
material
visit
our
website:

EUCLID
-‐
Providing
Linked
Data
137

@euclid_project
euclidproject
euclidproject

http://www.euclid-‐project.eu

Other
channels:

eBook
Course

ESWC SS 2013 - Tuesday Tutorial 1 Maribel Acosta and Barry Norton: Providing Linked Data

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