barcamprdu linkeddata
TRANSCRIPT
Linked DataBarCampRDU 2010
Intro slides - Dave Johnson
Monday, October 25, 2010
Motivations
Data model for machine readable web
Monday, October 25, 2010
HTML is great for people with browsers
Monday, October 25, 2010
Not so great for software that needs to extract meaningful data from web
Monday, October 25, 2010
Motivations
Data model for HTTP / REST based web services
Monday, October 25, 2010
HTTP is pretty good for creating, retrieving, updating and deleting resources on the web
Image by Paul Downeyhttp://www.flickr.com/photos/psd/421186578/
Monday, October 25, 2010
XML and JSON based formats are pretty good for representing resources
Photo by Alex Waterhouse-Haywardhttp://blog.alexwaterhousehayward.com/2007_11_14_archive.html
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But, just because a resource is represented in XML or JSON doesn’t mean you know how to parse it or what the data means
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Enter RDF• Resource Description Framework (RDF)
• Simple data model
• Resources identified by URI
• Resources have property values
• Property values can be literal values
• Or URI links to other resources
• Property value also known as triple
• Subject - resource (identified by URI)
• Predicate - property type (identified by URI)
• Object - value of property
• RDF data can be represented in XML, JSON and other formats
• If it’s an RDF representation then you know how to parse it or what the data means
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Common vocabularies• RDF provides ways to specify vocabularies of
properties (e.g. http://www.w3.org/TR/rdf-schema/, http://www.w3.org/TR/owl-ref/ )
• And ontologies: resource classes with agreed upon sets properties
• Two of many examples:
abstract, accessRights, accrualMethod, accrualPeriodicity, accrualPolicy, alternative, audience, available, bibliographicCitation, conformsTo, contributor, coverage, created, creator, date, dateAccepted, dateCopyrighted, dateSubmitted, description, educationLevel, extent, format, hasFormat, hasPart, hasVersion, identifier, instructionalMethod, isFormatOf, isPartOf, isReferencedBy, isReplacedBy, isRequiredBy, issued, isVersionOf, language, license, mediator, medium, modified, provenance, publisher, references, relation, replaces, requires, rights, rightsHolder, source, spatial, subject, tableOfContents, temporal, title, type, valid, contributor, coverage, creator, date, description, format, identifier, language, publisher, relation, rights, source, subject, title, type
Classes: | Agent | Document | Group | Image | LabelProperty | OnlineAccount | OnlineChatAccount | OnlineEcommerceAccount | OnlineGamingAccount | Organization | Person | PersonalProfileDocument | Project |
Properties: | account | accountName | accountServiceHomepage | age | aimChatID | based_near | birthday | currentProject | depiction | depicts | dnaChecksum | familyName | family_name | firstName | focus | fundedBy | geekcode | gender | givenName | givenname | holdsAccount | homepage | icqChatID | img | interest | isPrimaryTopicOf | jabberID | knows | lastName | logo | made | maker | mbox | mbox_sha1sum | member | membershipClass | msnChatID | myersBriggs | name | nick | openid | page | pastProject | phone | plan | primaryTopic | publications | schoolHomepage | sha1 | skypeID | status | surname | theme | thumbnail | tipjar | title | topic | topic_interest | weblog | workInfoHomepage | workplaceHomepage | yahooChatID |
FOAF
Monday, October 25, 2010
ExampleBlog entry in RDF / Turtle
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix dcterms: <http://purl.org/dc/terms/> .@prefix foaf: <http://http://xmlns.com/foaf/0.1/> .@prefix oslc: <http://open-services.net/ns/core#> .@prefix oslc_blog: <http://open-services.net/ns/bogus/blogs#> .
<http://example.com/blogs/entry/1> rdf:type oslc_blog:Entry ; dcterms:content "Anything dirty or dingy or dusty. \n Anything ragged or rotten or rusty." ; dcterms:creator [ rdf:type foaf:Person ; foaf:name "Oscar T. Grouch" ] ; dcterms:modified "2002-10-10T12:00:00-05:00" ; dcterms:title "I love trash" .
URI of this resource http://example.com/blogs/entry/1
Monday, October 25, 2010
ExampleChange Request in RDF / XML <?xml version="1.0" encoding="UTF-8"?>
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:dcterms="http://purl.org/dc/terms/" xmlns:oslc="http://open-services.net/ns/core#" xmlns:oslc_cm="http://open-services.net/ns/cm#" xmlns:ex="http://example.com/bugtracker">
<rdf:Description rdf:about="http://example.com/bugs/2314"> <rdf:type rdf:resource="http://open-services.net/ns/cm#ChangeRequest" />
<dcterms:identifier> 00002314 </dcterms:identifier> <oslc:shortTitle>Bug 2314</oslc:shortTitle> <dcterms:title> Invalid installation instructions </dcterms:title> <dcterms:type> Defect </dcterms:type> <oslc:instanceShape rdf:resource="http://example.com/shapes/defect" /> <dcterms:description> Invalid installation instructions indicating invalid patches to be applied. </dcterms:description>
...</rdf:RDF>
URI of this resource http://example.com/bugs/2314
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ExampleRDFa embedded in HTML
<div about="/alice/posts/trouble_with_bob" xmlns:dc="http://purl.org/dc/elements/1.1/">
<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>
Monday, October 25, 2010
Linked Data
Tim Berners-Lee outlined four principles of Linked Data in his Design Issues: Linked Data note, paraphrased along the following lines:
1. Use URIs to identify things.2. Use HTTP URIs so that these things can be referred to and
looked up ("dereferenced") by people and user agents.3. Provide useful information about the thing when its URI is
dereferenced, using standard formats such as RDF/XML.4. Include links to other, related URIs in the exposed data to
improve discovery of other related information on the Web.
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Problems with RDF
• Representations
• RDF/XML is a nightmare of complexity
• RDF/JSON not really there yet
• Perceptions of complexity
• RDF/XML doesn’t help
• Weird terminology: blank nodes, triples and reification, etc.
• I need a triple-store and a SPARQL query engine?
• Slow adoption, has it crossed the chasm?
But... RDF is not RDF/XML, you can use other formats
But... there are some JSON representations out there
Yes, there is some learning curve but the underlying data
model is simple: resources with property values
You might need an RDF parser but not a full stack of RDF technology to benefit
Who knows? We’ll review some evidence of momentum later...
Monday, October 25, 2010
Linked Data momentumLinked Data major part of upcoming Drupal 7 release
http://sf2010.drupal.org/conference/sessions/story-rdf-drupal7-and-what-it-means-web-large
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Linked Data momentumUS government
using Linked Data to provide access to government data
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Linked Data momentumUK government
using Linked Data to provide access to government data
Monday, October 25, 2010
Linked Data momentum
http://www.readwriteweb.com/archives/how_best_buy_is_using_the_semantic_web.php
Best Buy using Linked Data and RDFa to increase traffic and
provide better service to customers
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Linked Data momentum
http://www.youtube.com/watch?v=B2vqL8fujgE
http://open-services.net
OSLC specs build on Linked Data to enable integration of software development tools
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How to benefit
• Web site designers and operators
• Use RDFa to mark-up data in your web pages
• Benefits:
• Search engines can index your data more effectively
• Software can more easily parse and make sense of your data
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How to benefit• REST API developers
• Use RDF as the data model for your REST web services
• Define your resources in terms of RDF properties
• Provide RDF representations of your resources
• Benefits:
• You don’t have to invent a new data model or a new XML or JSON format
• You can use standard property types
• And common vocabulary means easier inter-op with other web apps
Monday, October 25, 2010
Learn more
• O’Reilly Programming the Semantic Web
• http://oreilly.com/catalog/9780596153823
• W3C Linked Data initiative
• http://esw.w3.org/LinkedData
• Tim Berners-Lee: The next web of open linked data
• http://www.youtube.com/watch?v=OM6XIICm_qo
• Tim Berners-Lee: Linked Data is Blooming: Why You Should Care
• http://www.readwriteweb.com/archives/linked_data_is_blooming_why_you_should_care.php
Monday, October 25, 2010