Linked Open Data - Seminar 25.04.12

Rajendra [email protected]

Open

Linked^ Data

mailto:[email protected]

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Outline

Web evolution

Semantic Web

Why we need it?

Linked Data Paradigm

Tools

JSON-LD

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Web Evolution

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From Gopher to Super-Mashups

http://reegle.info/countries

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Why do we want to add meaning to data ?

When a computer understands what data means, it can do search, reasoning and combining

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Meaning is about understanding

To understand we need a language

A language starts with words

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Things mean something in words

Online, we describe things with XML

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Look at my coin collection

The first coin is called “Silver Tram” and is from Armenia. It was made in 1246-47 AD.

The second coin is called “Gold Stater of Lahor” and is from India. It was made in 127-151 AD.

< ... etc >

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<?xml version="1.0" encoding="ISO-8859-1"?>

<collection name=”My coin collection">

<coin> <title>Silver Tram</title>

<country>Armenia</country> <year>1246-47 AD</year> </coin> <coin> <title>Gold Stater of

Lahor</title> <country>India</country> <year>127-151 AD</year> </coin></collection>

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We can’t understand words alone. We also need grammar

Online grammar is RDF (Resource Description Framework)

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This coin is from India

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This coin is from India

subject

predicate

object

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With RDF Schema we can define concepts and make simple relations between them

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This coin is from India, hence from South Asia

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But, RDF schema is limited

A language needs more expression and logic to make good reasoning possible

That’s why OWL (The Web Ontology Language) was invented

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Next, to reason you need rules

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I got this coin from my

grandfather.

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The rule for calling someone my grandfather is that one of my parents has a father

mother or fatherIson of father

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Rules are formulated in Rule Language

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<ruleml:imp>

<ruleml:_rlab ruleml:href="#example1"/>

<ruleml:_body>

<swrlx:individualPropertyAtom swrlx:property="hasParent">

<ruleml:var>x1</ruleml:var>


</swrlx:individualPropertyAtom>

<swrlx:individualPropertyAtom swrlx:property="hasFather">




</ruleml:_body>

<ruleml:_head>

<swrlx:individualPropertyAtom swrlx:property="hasGrandfather">




</ruleml:_head>

</ruleml:imp>

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So,

Words in XMLGrammar in RDF (schema) and OWLRules in RL

There are a lot of things, that can be described using standard formats

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Suppose, I want to search for a specific coin

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“I want all the golden coins, designed in Asia, but used in the Europe, between 1958 and 1989”

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We can use SPARQL (Protocol and RDF Query Language)

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Because the Web is decentralized and data is in many places, not only language

is important

Exchange of data between different DB for knowledge creation is an ultimate goal

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To make a connection a machine needs a source For this, we use resource identifiers

Best known resource identifier is the URI

which consists of a name (urn) and

a location (url)

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URI

URN

Gold Stater of Lahor

URL

http://www.mycollection.in/goldStater

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With all this background we are capable of using

the power of all different

data resources on the Web

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Linked Data vs. Semantic Web

The Semantic Web, or the Web of Data, is the ultimate goal

Linked Data provides the means to reach that goal

Linked Data helps build the Web of Data that later can be exploited by more advanced technologies such as intelligent agents

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Linked Data vs. Linked Open Data

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Databases store data to answer questions (1)

Persons Organisations

• How old is Rajendra?• Where does Rajendra work?• What is Rajendra interested

in?

• When was VF founded?• Where is VF located?• What can VF do for me?

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Databases store data to answer questions (2)

name date_birth work_place

interests

Rajendra 08-08 Sogndal Linked Data

Svein …. …. ….


organisation

date_founded

location

services

VF 1985 Norway IT-Consulting & Research

nLink …. …. ….

• Rajendra is .. years old.• Rajendra works in Sogndal.• Rajendra is interested in

the Linked Data.

• VF was founded 27 years ago.

• VF is located in Norway.• VF offers IT-Consulting & Research.

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Data from Databases can be exposed to the Web via HTML


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Data from Databases can be accessed via APIs

getLocation(„VF“)


getWorkplace(„Rajendra“)

<workPlace>Sogndal</workPlace> <location>Norway</location>

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(Some) Information on the Web can be found via search engines

Google Questions won´t be answered necessarily

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But how to get answers on complex questions? (1)

Who is interested in „Linked Data“ and is working in the same country as VF is located?

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But how to get answers on complex questions? (2)


name date_birth work_place interests

Rajendra 08-08 Sogndal Linked Data

Svein …. …. ….


organisation

date_founded

location services

VF 1985 Norway IT-Consulting & Research

nLink …. …. ….

work_place

Sogndal

location

Norway

same thing?

same country?

Still no answer

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Is Mapping the solution?

work_place

Sogndal

location

Norway

Mapped!

same country?

Still not clear

….….….Svein

Computer Science

NTNU08-08Rajendra

courseuniversitydate_birthname

Students

And what, if we need to add another database?

What, if DB-ownerscan´t agree on acommon model?

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Mapping is no

solution for a distributed

Web of data

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Before I come up

with a solution,

let us understand four simple things

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Resources

work_place

location

place

isAisA

Norway

Sogndal

partOf

type

type

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URIs & Namespaces

geo:point

geonames:country

umbel:place

rdfs:subClassOf

dbpedia:Norway

dbpedia:Sogndal

p:subdivisionName

rdfs:subClassOf

rdf:type

dbpedia:Sogndal http://dbpedia.org/resource/Sogndal=

rdf:type

rdfs:subClassOf = http://www.w3.org/2000/01/rdf-schema#subClassOf

A namespace is an abstract container or environment created to hold a logical grouping of unique identifier or symbols.

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Ontologies

work_place

location

place

Person Organisation

University

worksFor

studiesAtisA

has

isAisA

has

Norway

Sogndal

partOf

type

type

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What, if each resource (classes and

individuals) had a URI?

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Expose data from databases as resources & triples on the Web

foaf:name foaf:birthday

foaf:based_near

foaf:topic_interest

Rajendra 08-08 dbpedia:Sogndal dbpedia:LinkedData

Svein …. …. ….

Persons

persons:Rajendra

persons:Svein

dbpedia:Sogndal

persons:Rajendra

foaf:based_near

Organisations

foaf:name

foaf:birthday

foaf:based_near

orgs:services

VF 1985 dbpedia:Norway IT-Consulting & Research

nLink …. …. ….

orgs:VF

orgs:nLink

dbpedia:Norway

orgs:VF

foaf:based_near

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Link data and do queries all over the Web

dbpedia:Sogndal

persons:Rajendra

foaf:based_near

dbpedia:Norway

orgs:VF

foaf:based_near


dbpedia:LinkedData

foaf:topic_interest

p:subdivisionName

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Link data from more than 40 datasets

Make use of more than 2 Billion triples!

http://esw.w3.org/topic/SweoIG/TaskForces/CommunityProjects/LinkingOpenData

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The Linking Open Data cloud diagram

http://richard.cyganiak.de/2007/10/lod/

Link data from more than 295 datasetsLast updated: 2011-09-19

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How to get answers on really complex questions?

dbpedia:Sogndal

persons:Rajendra

foaf:based_near

dbpedia:Norway

orgs:VF

foaf:based_near

Who is interested in „Linked Data“ and is working in a country where the unemployment rate is lower than 4%?

dbpedia:LinkedData

foaf:topic_interest

p:subdivisionName Scandinavia:Norgeowl:sameAs

3.6

Scandenavia:unemployment_rate_total

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New way to get knowledge and answers —not by searching the web, but by doing dynamic computations based on a vast collection of data, algorithms, and methods

http://www.wolframalpha.com/

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Comprehensive Knowledge Archive Network

http://no.ckan.net/Open Knowledge FoundationLicensed under the Open Database

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A collaboration between: Norwegian Press Association, Association of Norwegian Editors, Norwegian Union of Journalists, and Department of Journalism

http://www.offentlighet.no/Registeroffentlighet/Alle-registre

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Linked data ...

publishing data on the Web ...

... to enable integration, linking and reuse across silos

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Six Steps to Publishing Linked Data

1. Understand the Principles

2. Model Your Data

3. Choose URIs for Things in your Data

4. Setup Your Infrastructure

5. Link to other Data Sets

6. Describe and Publicise your Data

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Can’t we just publish data as files?pdf

easy to read and publish

Excel allows further processing and analysis

csv processing without need for proprietary tools

But ... structure of data not explained no connection between different data sets, silos static and fixed – can’t retrieve just slices relevant to problem

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Linked data

Apply the principles of the Web to publication of data

The Web: is a global network of pages each identified by a URL fetching a URL gives a document pages connected by links open, anyone can say anything about anything else

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Linked dataApply the principles to the web to publication of data

The linked data web: is a global network of things each identified by a URI fetching a URI gives a set of statements things connected by typed links open, anyone can say anything about anything else

Linked data is “data you can click on”

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Linked Data - Paradigm

Use URIs as names for things

Use HTTP URIs so that people can look up those names.

When someone looks up a URI, provide useful information.

Include links to other URIs. so that they can discover more things.

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LOD Benefits

other humans and applications caneasily access your data using Web

technologiesfollow the links in order to obtain

further contextual information

links to your data and search engine indices can increase the visibility of your data

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JSON-LD - JSON for Linking Data

JSON-LD (JavaScript Object Notation for Linking Data) is a lightweight Linked Data format that gives your data context. It is easy for humans to read and write. It is easy for

machines to parse and generate. It is based on the already successful JSON format and

provides a way to help JSON data interoperate at Web-scale.

If you are already familiar with JSON, writing JSON-LD is very easy.

These properties make JSON-LD an ideal Linked Data interchange language for JavaScript environments, Web service, and unstructured databases such as CouchDB and MongoDB.http://json-ld.org/spec/latest/json-ld-syntax/

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This RDF model in standard XML notation

<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:dc="http://purl.org/dc/elements/1.1/"> <rdf:Description rdf:about="/wiki/Tony_Benn"> <dc:title>Tony Benn</dc:title> <dc:publisher>Wikipedia</dc:publisher> </rdf:Description> </rdf:RDF>

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written in JSON-LD like this:

{ "@context": { "title": "http://purl.org/dc/elements/1.1/title", "publisher": "http://purl.org/dc/elements/1.1/publisher" }, "@id": "/wiki/Tony_Benn", "title": "Tony Benn", "publisher": "Wikipedia" }

A context is used to allow developers to use aliases for IRIs.

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JSON-LD object

An Internationalized Resource Identifier (IRI) is a mechanism for representing unique

identifiers on the web. In Linked Data, IRIs (or URI references) are

commonly used for describing entities and properties.

{ "a": "Person", "name": "Manu Sporny", "homepage": "http://manu.sporny.org/" "avatar": "http://twitter.com/account/profile_image/manusporny" }

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Unambiguous Identifiers for JSON

If a set of terms, like Person, name, and homepage, are defined in a context, and that context is used to resolve the names in JSON objects, machines could automatically expand the terms to something meaningful and unambiguous

{ "http://www.w3.org/1999/02/22-rdf-syntax-ns#type": "http://xmlns.com/foaf/0.1/Person", "http://xmlns.com/foaf/0.1/name": "Manu Sporny", "http://xmlns.com/foaf/0.1/homepage": "http://manu.sporny.org" "http://rdfs.org/sioc/ns#avatar": "http://twitter.com/account/profile_image/manusporny" }

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JSON-LD Example

Let's start by building up a fictitious bike store called "Links Bike Shop". We've already got our bike store setup athttp://store.example.com/ and are using linked data principles.

Here's some of the URLs:

http://store.example.com/: The home page of the store.

http://store.example.com/products/links-swift-chain: A chain product.

http://store.example.com/products/links-speedy-lube: A chain lube product.

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We want to start creating some linked data for this fictitious store and start with rough JSON data on the store itself.

{

"@id": "http://store.example.com/",

"@type": "Store",

"name": "Links Bike Shop",

"description": "The most \"linked\" bike store on earth!"

}

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Next let's create some rough data for our two premier products{ "@id":

"http://store.example.com/products/links-swift-chain",

"@type": "Product", "name": "Links Swift Chain", "description": "A fine chain with many

links.", "category":

["http://store.example.com/categories/parts", "http://store.example.com/categories/chains"],

"price": "10.00", "stock": 10}

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{

"@id": "http://store.example.com/products/links-speedy-lube",

"@type": "Product",

"name": "Links Speedy Lube",

"description": "Lubricant for your chain links.",

"category": ["http://store.example.com/categories/lubes", "http://store.example.com/categories/chains"],

"price": "5.00",

"stock": 20

}

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To make this into a full JSON-LD document we combine the data, add a @context, and adjust some values.{

"@id": "http://store.example.com/",

"@type": "Store",

"name": "Links Bike Shop",

"description": "The most \"linked\" bike store on earth!",

"product": [

...

...

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],

"@context": {

"Store": "http://ns.example.com/store#Store",

"Product": "http://ns.example.com/store#Product",

"product": "http://ns.example.com/store#product",

"category": {

"@id": "http://ns.example.com/store#category",

"@type": "@id"

},

"price": "http://ns.example.com/store#price",

"stock": "http://ns.example.com/store#stock",

"name": "http://purl.org/dc/terms/title",

"description": "http://purl.org/dc/terms/description",

"p": "http://store.example.com/products/",

"cat": "http://store.example.com/category/"

}

}

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Publishing Solutions and Tools

Triplify

Goal: expose semantics available in RDBMS as simple as possible

Available for most popular Web app languages PHP (ready), Ruby/Python (under dev.)

Works with most popular Web app databases MySQL, PHP-PDO DBs (SQLite, Oracle, DB2, MS

SQL, PostgreSQL)

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Virtuoso RDF Views

transforms the result of SQL SELECT statements into RDF

mapping steps define RDFS class IRIs for each table define construction of subject IRIs from primary key

column values define construction of predicate IRIs from each non-key

column

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Relational Databases RDF & Ontologies

Data Model Relational(tables, columns, rows)

Triples(subject, predicate, object)

Schema and data separation

Implicit information

Scalability

Schema flexibility

Web data integration readiness

Marrying DBs with RDF & Ontologies

Using DBs for storage and querying of RDF & ontologies

Publishing DB content as RDF

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DBpedia is a community effort to extract structured information from Wikipedia and to make this information available on the Web. DBpedia allows you to ask sophisticated queries against Wikipedia, and to link other data sets on the Web to Wikipedia data.

The DBpedia knowledge base currently describes more than 2.6 million things, including at least 213,000 persons, 328,000 places, 57,000 music albums, 36,000 films, 20,000 companies. The knowledge base consists of 274 million pieces of information (RDF triples).

http://dbpedia.org/

DBpedia and all other linked data is searchable with SPARQL

http://en.wikipedia.org/wiki/SPARQL

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Open Streetmap

OpenStreetMap is a free editable map of the whole world. It is made by people like you.

OpenStreetMap allows you to view, edit and use geographical data in a collaborative way from anywhere on Earth.

www.openstreetmap.org

GeoNamesThe GeoNames geographical database is available for download free of charge under a creative commons attribution license. It contains over eight million geographical names and consists of 6.5 million unique features.www.geonames.org

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Creating Open DataPublic Domain – Only after the expiration of copyright

Science Commons protocol for open data

Creative Commons Zero Public Domain Dedication & License with Community Norms

o Avoid Technical protection measures

o Give credit where credit’s due

o Use Open formats

o Let others know!

o Share your work too!

Photo by suttonhoo @ Flickr, CC BY-NC-SA

http://www.flickr.com/photos/suttonhoo22/

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Examples

http://data-gov.tw.rpi.edu/wikihttp://dbrec.net/http://fanhu.bz/http://data.nytimes.com/schools/schools.htmlhttp://sig.mahttp://visinav.deri.org/semtech2010/

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The road to open knowledge begins here!

Thank you !

Linked Open Data - Seminar 25.04.12

Technology

Transcript of Linked Open Data - Seminar 25.04.12