Semantic Web
Languages and Schemata(1) Metadata and RDF

Hideaki Takeda
National Institute of Informatics
takeda＠nii.ac.jp
Hideaki Takeda / National Institute of Informatics

Linked Datall

Languages for Semantic Webn Languages for RDF
u Turtle
u JSON-LD
u RDFan Languages for RDF queryu SPARQL
Schemata

Hideaki Takeda / National Institute of Informatics

A Layer model for Semantic Weblll

RDF (Resource Description Framework)
n The most primitive model for metadata description
u SVO modelu Entity-Relation Modelu Semantic net
RDF Scheman Addition of “concept” to RDF
u class-subclass，constraints
OWL
n More general concept description language
u Logical consistencyu Various class expressionsu Various constraints

Tim Berners-Lee http://www.w3.org/2002/Talks/09-lcs-sweb-tbl/
Hideaki Takeda / National Institute of Informatics

Metadata
What is metadata?
n Data about datan What one can say about any information objectl What is described as metadata?
n Content relates to what the object contains or is about, and is
intrinsic to an information object.
n Context indicates the who, what, why, where, how aspects
associated with the object's creation and is extrinsic to an
information object.
n Structure relates to the formal set of associations within oramong individual information objects and can be intrinsic or
extrinsiclSetting the State, Anne J.Gilliand-Swetland, Introduction to Metadata – Pathways to Digital
Information, Murthsa Baca (ed.), Getty Information Institute.
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Metadata
Metadata to individual information objects
n Bibliography，Dublin Corel Metadata to part or structure of information objects
n Drawings，RDF，RDFS, OWLl

Type：tractor
Owner：Taro
Product year：2002

Body
Axis:
Connect body to wheel

Wheel
Hideaki Takeda / National Institute of Informatics

Dublin Core
Framework for “bibliographic” style metadatal Simplicity “Pidgins”
n A few vocabularyn A simple structurel 15 elements: Dublin Core Metadata Element Set
n Creator, Title, Subject/Keywords, Description, Publisher,
Contributor, Date, Resource Type, Format, Resource Identifier,Source, , Language, Relation, Coverage, Rights Managementn All elements can be omitted and duplicated in any orderl

Hideaki Takeda / National Institute of Informatics

Dublin CorelAn example by PDF<rdf:Description about=''
xmlns='http://purl.org/dc/elements/1.1/'
xmlns:dc='http://purl.org/dc/elements/1.1/'><dc:creator>Hideaki Takeda</dc:creator><dc:title>A GENERAL FRAMEWORK FOR MODELINGOF SYNTHESIS</dc:title><dc:description>INTEGRATION OF THEORIES OFSYNTHESIS</dc:description></rdf:Description>
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RDF (Resource Description Framework)
A framework to describe metadatal Separation of model and syntax
l W3C Recommendation (2004)l

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RDF Modell

Elementn Resource:
u URI(Universal Resource Identifier)u Literal(string)l No need to be specified by Web
n Property:
u Attribute when describing resources
u URI or Literal just as Resourcen Statement: triad of resource, property, and resource

Hideaki Takeda / National Institute of Informatics

RDF modelllStatementn Creator of http://www-kasm.nii.ac.jp/~takeda is “Hideaki Takeda”
Structuren Resource (subject): http://www-kasm.nii.ac.jp/~takeda
n Property (predicate): Creatorn Value (object): “Hideaki Takeda”
http://www-kasm.nii.ac.jp/~takeda

Resource

Creator

Property“Hideaki Takeda”

Value

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RDF modellCreator of http://www-kasm.nii.ac.jp/~takeda is http://www.nii.ac.jp/staffid/123456 which
has name “Hideaki Takeda” and email “takeda@nii.ac.jp” ．

http://www-kasm.nii.ac.jp/~takeda

Creator

http://www.nii.ac.jp/staffid/123456

name“Hideaki Takeda”

email“takeda@nii.ac.jp”

Hideaki Takeda / National Institute of Informatics

RDF modellCreator of http://www-kasm.nii.ac.jp/~takeda has name “Hideaki
Takeda” email “takeda@nii.ac.jp” ．
http://www-kasm.nii.ac.jp/~takeda

Creatorname“Hideaki Takeda”

email“takeda@nii.ac.jp”

Hideaki Takeda / National Institute of Informatics

RDF/TurtlelCreator of http://www-kasm.nii.ac.jp/~takeda is “Hideaki Takeda”
http://www-kasm.nii.ac.jp/~takeda

Resource

Creator

Property“Hideaki Takeda”

Value@prefix dc: <http://dublincore.org/2001/08/14/dces#> .
<http://www-kasm.nii.ac.jp/~takeda> dc:Creator "Hideaki Takeda" .

Hideaki Takeda / National Institute of Informatics

RDF/TurtlelCreator of http://www-kasm.nii.ac.jp/~takeda is http://www.nii.ac.jp/staffid/123456 which
has name “Hideaki Takeda” and email “takeda@nii.ac.jp” ．

http://www-kasm.nii.ac.jp/~takeda

Creator

http://www.nii.ac.jp/staffid/123456

name“Hideaki Takeda”

email“takeda@nii.ac.jp”@prefix dc: <http://dublincore.org/2001/08/14/dces#> .
@prefix ex: <http://example.org/schema> .
<http://www-kasm.nii.ac.jp/~takeda> dc:Creator<http://www.nii.ac.jp/staffid/123456> .
<http://www.nii.ac.jp/staffid/123456> ex:name "Hideaki Takeda" .
<http://www.nii.ac.jp/staffid/123456> ex:email "takeda@nii.ac.jp" .
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RDF syntax
Creator of http://www-kasm.nii.ac.jp/~takeda has name “Hideaki
Takeda” email “takeda@nii.ac.jp” ．
http://www-kasm.nii.ac.jp/~takeda

Creatorname“Hideaki Takeda”

email“takeda@nii.ac.jp”@prefix dc: <http://dublincore.org/2001/08/14/dces#> .
@prefix ex: <http://example.org/schema> .
<http://www-kasm.nii.ac.jp/~takeda> dc:Creator [ex:name "Hideaki Takeda" ;ex:email "takeda@nii.ac.jp"] .
Hideaki Takeda / National Institute of Informatics

RDFS (RDF Schema)lllStronger knowledge representation modeln RDF: ER model，semantic net
n RDF Schema: Frame model，object-oriented paradigmu Minimal definitionu Property-centered approach
RDFS is defined as extension of RDF
RDFS gives definitions of RDF descriptions

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RDFS
l

l

l

Class Definitionn rdfs:Resourcen rdfs:Classn rdf:Propertyn rdfs:ConstraintPropertyn rdfs:Literal
Property Definitionn rdf:typen rdfs:subClassOf
n rdfs:subPropertyOf
n rdfs:commentn rdfs:labeln rdfs:seeAlso
n rdfs:isDefinedBy
ConstraintProperty Definitionn rdfs:range
n rdfs:domain

RDFSのClass階層
Resource Description Framework(RDF) Schema Specification 1.0
http://www.w3.org/TR/2000/CR-rdf-schema-20000327/

Hideaki Takeda / National Institute of Informatics

RDF Schema
rdfs:Classl rdfs:SubclassOf
n Detailed classn Multiplen Transivity
l rdf:typen Indicate an instance of aclass
l rdf:propertyn Attributel rdfs:subPropertyOfn Detailed propertyn TransivitylRangen Only one
u No cardinalityl Domainn Multiple (or)lHideaki Takeda / National Institute of Informatics

AnimalRDF Schema“The class of person”@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema> .
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns> .
@prefix ex: <http://example.org/> .

rdfs:comment

ex:maritalStatusa rdf:Property ;rdfs:range ex:MaritalStatus ;rdfs:domain ex:Person .

PersondmaritalStatus

ex:Persona rdfs:Class ;rdfs:comment "The class of people." ;rdfs:subClassOf<http://www.w3.org/2000/03/example/classesAnimal> .
ex:MaritalStatus a rdfs:Class .
ex:Married a ex:MaritalStatus .
ex:Divorced a ex:MaritalStatus .
ex:Single a ex:MaritalStatus .
ex:Widowed a ex:MaritalStatus .

s
d

d

r

age

MaritalStatusrssn

rdfs:comment

IntegerttMarriedtSingleWindowedt
Divorced

ex:ssna rdf:Property ;rdfs:comment "Social Security Number" ;rdfs:range <http://www.w3.org/2000/03/example/classesInteger> ;rdfs:domain ex:Person .

“Social Security Number”

t = rdf:typed = rdfs:domainr = rdfs:range= class= class instance= property

ex:agea rdf:Property ;rdfs:range <http://www.w3.org/2000/03/example/classesInteger> ;rdfs:domain ex:Person .

Resource Description Framework(RDF) Schema Specification 1.0
http://www.w3.org/TR/2000/CR-rdf-schema-20000327/

Hideaki Takeda / National Institute of Informatics

Serialization of RDF
RDF is an abstract model represented as a graphl RDF serialization gives the format to describe RDF statements as atextual expression.
l Different serialization formats
n RDF/XMLn Turtlen N-Triples
n JSON-LD
n RDFal

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TurtlelSyntaxn[Subject] [Predicate] [Object] .
<http://example.org/#spiderman><http://www.perceive.net/schemas/relationship/enemyOf><http://example.org/#green-goblin> .

n[Subject] [Predicate1] [Object1] ;[Predicate2] [Object2] .
<http://example.org/#spiderman><http://www.perceive.net/schemas/relationship/enemyOf><http://example.org/#green-goblin> ;<http://xmlns.com/foaf/0.1/name> "Spiderman" .

n[Subject] [Predicate] [Object1] ,[Object2] .
<http://example.org/#spiderman> <http://xmlns.com/foaf/0.1/name>“Spiderman”@en,“スパイダーマン"@ja .
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Turtlel

IRIn Absolute IRI: ex. <http://example.org/#green-goblin>n Relative IRI: ex.
@base <http://example.org/> .
#green-goblin <http://www.perceive.net/schemas/relationship/enemyOf>#spiderman .
<http://example.org/#green-goblin><http://www.perceive.net/schemas/relationship/enemyOf><http://example.org/#spiderman> .

n Prefixed name: a prefix label + local part@base <http://example.org/> .
@prefix rel: <http://www.perceive.net/schemas/relationship/> .
#green-goblin rel:enemyOf #spiderman .
<http://example.org/#green-goblin><http://www.perceive.net/schemas/relationship/enemyOf><http://example.org/#spiderman> .
Hideaki Takeda / National Institute of Informatics

Turtlel

RDF literals@prefix foaf: <http://xmlns.com/foaf/0.1/> .
<http://example.org/#green-goblin> foaf:name "Green Goblin" .
<http://example.org/#spiderman> foaf:name "Spiderman".

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Turtlel

Numbers
Data Type
xsd:integer
xsd:decimal

xsd:double

Abbreviated Lexical
-5
-5.0

4.2E9

Description"-5"^^xsd:integer

Integer values may be written as an optional sign and a series of digits. Integers
match the regular expression "[+-]?[0-9]+".

"-5.0"^^xsd:decimal

Arbitrary-precision decimals may be written as an optional sign, zero or moredigits, a decimal point and one or more digits. Decimals match the regularexpression "[+-]?[0-9]*¥.[0-9]+".

"4.2E9"^^xsd:double

Double-precision floating point values may be written as an optionally signed
mantissa with an optional decimal point, the letter "e" or "E", and an optionally
signed integer exponent. The exponent matches the regular expression "[+-]?[09]+" and the mantissa one of these regular expressions: "[+-]?[0-9]+¥.[0-9]+", "[+]?¥.[0-9]+" or "[+-]?[0-9]".

n Ex.
@prefix : <http://example.org/elements> .
<http://en.wikipedia.org/wiki/Helium>:atomicNumber 2 ; # xsd:integer:atomicMass 4.002602 ; # xsd:decimal:specificGravity 1.663E-4 . # xsd:doublel Booleans@prefix : <http://example.org/stats> .
<http://somecountry.example/census2007> :isLandlocked false . # xsd:boolean
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TurtlelBlank nodes@prefix foaf: <http://xmlns.com/foaf/0.1/> .
_:alice foaf:knows _:bob .
_:bob foaf:knows _:alice .

l

Nesting Unlabeled Blank Nodes in Turtle@prefix foaf: <http://xmlns.com/foaf/0.1/> .
# Someone knows someone else, who has the name "Bob".
[] foaf:knows [ foaf:name "Bob" ] .
@prefix foaf: <http://xmlns.com/foaf/0.1/> .
[ foaf:name "Alice" ] foaf:knows [foaf:name "Bob" ;foaf:knows [ foaf:name "Eve" ] ;foaf:mbox <bob@example.com> ] .
_:a foaf:knows "Alice" .
_:a foaf:knows _:b .
_:b foaf:name "Bob" .
_:b foaf:knows _:c .
_:c foaf:name "Eve" .
_:b foaf:mbox <bob@example.com> .
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N-Triples
Line-based RDF Graphl Pros and cons in comparison with Turtle
n Prosu Can process line by linen Consu Bigger datal

Hideaki Takeda / National Institute of Informatics

l

N-Triples

IRI Representations
TurtleN-Triplesexampleabsolute IRI

Yes

yes

<http://a.example/some/path/>

relative IRI

Yes

no

</some/path/>prefixed name

yes

no

rdfs:label

a for the predicate rdf:type

yes

no

a

l

Literal Representations
TurtleN-Triplesexamplesingle-quoted single-line lexical representation

yes

no

'some literal'

double-quoted single-line lexical representation

yes

yes

"some literal"

single-quoted multi-line lexical representation

yes

no

'''some literal'''double-quoted multi-line lexical representation

yes

no

"""some literal"""abbreviated numeric

yes

no

13

abbreviated boolean

yes

no

true

l

Blank Node Representations in N-Triples and Turtle
exampleTurtleN-Tripleslabeled blank node

yes

yes

<http://a.example/who#Alice> <http://xmlns.com/foaf/0.1/knows> _:bob .

anonymous node

yes

no

<http://a.example/who#Alice> foaf:knows [] .

blank node property list

yes

no

<http://a.example/who#Alice> foaf:knows [ foaf:name "Bob" ] .

Hideaki Takeda / National Institute of Informatics

JSON-LD
An extension of JSON for semantic datan But still within JSON syntax
l Introduction of reserved names starting with ‘@’
n @context
n @typel Use for schema.org
lHideaki Takeda / National Institute of Informatics

JSON-LDl

Example 1{"name": "Manu Sporny","homepage": "http://manu.sporny.org/","image": http://manu.sporny.org/images/manu.png}

Hideaki Takeda / National Institute of Informatics

JSON-LDl

Example 2{"http://schema.org/name": "Manu Sporny","http://schema.org/url":{
The '@id' keyword means 'This"@id": http://manu.sporny.org/
value is an identifier that is an IRI'}
"http://schema.org/image":{"@id": "http://manu.sporny.org/images/manu.png"}}
Hideaki Takeda / National Institute of Informatics

JSON-LDl

Example 3{"@context": {"name": "http://schema.org/name","image": {"@id": "http://schema.org/image","@type": "@id"},"homepage": {"@id": "http://schema.org/url","@type": "@id"}}}This means that 'name' is shorthandfor 'http://schema.org/name'
This means that 'image' isshorthand for'http://schema.org/image
This means that a string value
associated with 'image'should be interpreted as an
identifier that is an IRI
This means that 'homepage' isshorthand for'http://schema.org/url''This means that a string value
associated with 'homepage'should be interpreted as an
identifier that is an IRI
Hideaki Takeda / National Institute of Informatics

l

Example 4

Referring JSON-LD context
document{"@context": "https://json-ld.org/contexts/person.jsonld","name": "Manu Sporny","homepage": "http://manu.sporny.org/","image": "http://manu.sporny.org/images/manu.png"}

Hideaki Takeda / National Institute of Informatics

JSON-LDl

Example 5{"@context": {"name": "http://schema.org/name","image": {"@id": "http://schema.org/image","@type": "@id"},"homepage": {"@id": "http://schema.org/url","@type": "@id"}}"name": "Manu Sporny","homepage": "http://manu.sporny.org/","image": "http://manu.sporny.org/images/manu.png"
Hideaki Takeda / National Institute of Informatics}

l

Example 6

JSON-LD @type{"@context": {...
"givenName": "http://schema.org/givenName","familyName": "http://schema.org/familyName"},"@id": "http://me.markus-lanthaler.com/","@type": "http://schema.org/Person","givenName": "Markus","familyName": "Lanthaler",...
}l

Example 7{"@context": {...
"Person": "http://schema.org/Person"},"@id": "http://example.org/places#BrewEats","@type": "Person",

The value of a @type key may also
be a term defined in the active
context:
Hideaki Takeda / National Institute of Informatics

JSON-LD Referring objectslExample 8{"@context": {"@vocab": "http://xmlns.com/foaf/0.1/","knows": {"@type": "@id"}},"@id": "http://manu.sporny.org/about#manu","@type": "Person","name": "Manu Sporny","knows": "https://greggkellogg.net/foaf#me"

declare a default vocabulary
from which all terms derive,
without having to declare specificmappings for each term (as you
normally do in a @context).

}

Hideaki Takeda / National Institute of Informatics

JSON-LD embeddinglExample 9{"@context": {"@vocab": "http://xmlns.com/foaf/0.1/"},"@id": "http://manu.sporny.org/about#manu","@type": "Person","name": "Manu Sporny","knows": {"@id": "https://greggkellogg.net/foaf#me","@type": "Person","name": "Gregg Kellogg"}}
Hideaki Takeda / National Institute of Informatics

Use of JSON-LD with schema.org<script type="application/ld+json">{"@context": "https://schema.org","@type": "Organization","url": "http://www.example.com","name": "Unlimited Ball Bearings Corp.","contactPoint": {"@type": "ContactPoint","telephone": "+1-401-555-1212","contactType": "Customer service"}}</script>

Hideaki Takeda / National Institute of Informatics

<script type="application/ld+json">{"nutrition": {"@type": "NutritionInformation","@context": "https://schema.org/","@type": "Recipe","name": "Grandma's Holiday Apple Pie","author": "Elaine Smith","image": "http://images.edgegeneralmills.com/56459281-6fe6-4d9d-984f385c9488d824.jpg","description": "A classic apple pie.","aggregateRating": {"@type": "AggregateRating","ratingValue": "4","reviewCount": "276","bestRating": "5","worstRating": "1"},"prepTime": "PT30M","totalTime": "PT1H","servingSize": "1 medium slice","calories": "230 calories","fatContent": "1 g","carbohydrateContent": "43 g",},"recipeIngredient": ["1 box refrigerated pie crusts, softened as
directed on box","6 cups thinly sliced, peeled apples (6 medium)","..."],"recipeInstructions": ["1...","2..."]}</script>"recipeYield": "8",Hideaki Takeda / National Institute of Informatics

Google Structured data testing toolhttps://search.google.com/structured-data/testing-tool/u/0/

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Google Dataset Search

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https://data.gov.uk/dataset/baa48aa1-63d1-45d7-a44b-608c71c8f46d/disease-prevalence

Hideaki Takeda / National Institute of Informatics

<script type="application/ld+json">{"@context":"http://schema.org","@type":"Dataset","name":"Disease Prevalence","url":"https://data.gov.uk/dataset/baa48aa1-63d1-45d7-a44b-608c71c8f46d/disease-prevalence","includedInDataCatalog":{"@type":"DataCatalog","url":https://data.gov.uk},"creator":{"@type":"Organization","name":"OpenDataNI”},"description":"Data has been collected annually since 2004/05. A new GMS Contract was introduced in April 2004 and a fundamental funding
stream called the Quality and Outcomes Framework (QOF) was introduced at that time. QOF is a reward framework of indicators designed toremunerate general practices for providing good quality care to their patients. An important feature of QOF is the maintenance of registers whichallow prevalence of a number of long-term conditions to be calculated. Register counts and prevalence per 1,000 GP registered population are
published. Where registers are age-specific, prevalence per 1,000 age-specific population are also published.","license":{"@type":"CreativeWork","name":"Open Government Licence","text":null,"url":http://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/},"dateModified":"2016-10-19T10:00:20.345Z","keywords":"Health","distribution":[{"@type":"DataDownload","contentUrl":"https://www.opendatani.gov.uk/dataset/baa48aa1-63d1-45d7-a44b-608c71c8f46d/resource/b06c5b0f-fb6e-40aa83dd-e5e05435bbf3/download/disease-prevalence-trends2004-05-to-2015-16.ods","fileFormat":"ODS","name":"Disease Prevalence Trends 2004-05 to 2015-16”}]}</script>

Hideaki Takeda / National Institute of Informatics

RDFa
l

Add extra structured content to the (X)HTML pages
n adds new (X)HTML/XML attributes
u “RDF in attributes”
n Programs can extract those and turn into RDF
n Flexibility for using Literals and URI resources

Hideaki Takeda / National Institute of Informatics

Principles of RDFa
RDF contents are defined through XML attributes (no elements)l XML/HTML tree structure is usedl Various attributes are defined by RDFan Some attributes (@href, @rel) are also reusedl The text content can be also reusedlHideaki Takeda / National Institute of Informatics

Examples
http://example.com/alice/posts/trouble_with_bob<div xmlns:dc="http://purl.org/dc/elements/1.1/"><h2 property="dc:title">The trouble with Bob</h2><h3 property="dc:creator">Alice</h3>...
</div>

In N3<http://www.example.com/alice/posts/trouble_with_bob><http://purl.org/dc/elements/1.1/title> "The Trouble with Bob";<http://purl.org/dc/elements/1.1/creator> "Alice" .

Hideaki Takeda / National Institute of Informatics

<div xmlns:dc="http://purl.org/dc/elements/1.1/"><div about="/alice/posts/trouble_with_bob"><h2 property="dc:title">The trouble with Bob</h2><h3 property="dc:creator">Alice</h3>...
</div><div about="/alice/posts/jos_barbecue"><h2 property="dc:title">Jo's Barbecue</h2><h3 property="dc:creator">Eve</h3>...
</div>...
</div>

Hideaki Takeda / National Institute of Informatics

<div about="/alice/posts/trouble_with_bob"><h2 property="dc:title">The trouble with Bob</h2>
The trouble with Bob is that he takes much better photos than I do:<div about="http://example.com/bob/photos/sunset.jpg"><img src="http://example.com/bob/photos/sunset.jpg" /><span property="dc:title">Beautiful Sunset</span>
by<span property="dc:creator">Bob</span>.
</div></div>

Hideaki Takeda / National Institute of Informatics

<div typeof="foaf:Person" xmlns:foaf="http://xmlns.com/foaf/0.1/"><p property="foaf:name"> Alice Birpemswick </p><p> Email: <a rel="foaf:mbox" href="mailto:alice@example.com">alice@example.com</a></p><p> Phone: <a rel="foaf:phone" href="tel:+1-617-555-7332">+1 617.555.7332</a> </p></div>

Hideaki Takeda / National Institute of Informatics

<div xmlns:foaf="http://xmlns.com/foaf/0.1/" about="#me" rel="foaf:knows"><ul><li typeof="foaf:Person"><a property="foaf:name" rel="foaf:homepage" href="http://example.com/bob">Bob</a></li><li typeof="foaf:Person"><a property="foaf:name" rel="foaf:homepage" href="http://example.com/eve">Eve</a></li><li typeof="foaf:Person"><a property="foaf:name" rel="foaf:homepage" href="http://example.com/manu">Manu</a>
</li>
</ul>
</div>

Hideaki Takeda / National Institute of Informatics

Using RDFa
RDF Validatorn http://validator.w3.org/
u Also graph visualization for small datasetu Only RDF/XMLl RDF Distiller
n http://www.w3.org/2007/08/pyRdfa/ll

RDF Validator & Convertern http://rdfvalidator.mybluemix.net/l

RDF Converter & Visualizer
n http://www.easyrdf.org/converter
Hideaki Takeda / National Institute of Informatics

Which is the best serialization?
lll

RDF/XMLl JSON-LD
n Pros: Compatible with existing XMLn Pros:
processing systems
u well-used language (JSON)n Cons: Complicated and arbitrary, Not good forhuman readingu Simple syntax
n Recommended: Adding RDF data to then Cons:existing web services
u Not suitable for complex
Turtlestructuren Prosl RDFau Natural expression for RDF, text-basedn Pros: mixed with html
u Good for human readingn Cons: Difficult to edit, read, process
u Relatively good for machine processingn Cons: Require specific processingn Recommend
n Recommended: Dumped files
u Providing new web services with
N-Triples
RDF
n
n
n

Pros: Line-based
Cons: Bigger data
Recommended: internal data
Hideaki Takeda / National Institute of Informatics

RDF validatorlChecking RDF statements whether they are valid or not
n http://www.w3.org/RDF/Validator/
u RDF/XMLn http://www.rdfabout.com/demo/validator/
u RDF/XMLu Notation 3 (N-Triples, Turtle)

Hideaki Takeda / National Institute of Informatics