Introduction to Linked Data Platform (LDP)
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The Linked Data Platform (LDP) defines rules for HTTP operations on web resources to provide an architecture for read-write Linked Data on the web. Key concepts include resources, RDF sources, non-RDF sources, and containers. LDP uses HTTP requests and responses to create, retrieve, update, and delete resources. Resources can be contained within different types of containers, including basic, direct, and indirect containers. LDP provides a standard way to manage Linked Data using HTTP.
![Abraham_Lincoln label "Abraham Lincoln” .
Abraham_Lincoln birthDate "1809-02-12” .
Abraham_Lincoln profession "Lawyer” .
[. . .]
Abraham_Lincoln birthPlace Hodgenville,_Kentucky .
http://dbpedia.org/data/Abraham_Lincoln.n3
Linked Data
http://dbpedia.org/resource/Abraham_Lincoln
http://dbpedia.org/resource/Hodgenville,_Kentucky](https://image.slidesharecdn.com/introductiontoldp-150923131750-lva1-app6892/85/Introduction-to-Linked-Data-Platform-LDP-6-320.jpg)
![HTTP request
POST localhost/
Slug: logo.jpg
Content-Type: image/jpeg
Content- Length: 1020
[binary of the image goes here]
HTTP response
HTTP/1.1 201 Created
Location: http://localhost/logo.jpg
HTTP POST to create
a new Non-RDF Source
Binary data
…and here is the URL of
the new resource
Create a New Non-RDF Source](https://image.slidesharecdn.com/introductiontoldp-150923131750-lva1-app6892/85/Introduction-to-Linked-Data-Platform-LDP-15-320.jpg)
![HTTP request
GET localhost/hydraconnect2015/ HTTP/1.1
HTTP response
[the usual HTTP headers go here]
<localhost/hydraconnect2015/> a ldp:BasicContainer ;
dc:title “Hydra Connect 2015” ;
dc:subject ““Hydra conference in Minneapolis” ;
ldp:contains <localhost/hydraconnect2015/session1> .
Fetch the Basic Container
New triple automatically
added by the LDP Server
Adding an RDF Source to a Basic Container (2/2)](https://image.slidesharecdn.com/introductiontoldp-150923131750-lva1-app6892/85/Introduction-to-Linked-Data-Platform-LDP-18-320.jpg)
![Direct Container (2/2)
HTTP request
GET localhost/hydraconnect2015
HTTP response
[bunch of HTTP headers go here]
<localhost/hydraconnect2015/> a ldp:BasicContainer ;
dc:title “Hydra Connect 2015” ;
dc:subject ““Hydra conference in Minneapolis” ;
ldp:contains <localhost/hydraconnect2015/session1> ;
hasSpeaker <localhost/speakers/janedev> .
The membershipResource…
…pointing to the new
resource
…has new triple with
hasMemberRelation
predicate](https://image.slidesharecdn.com/introductiontoldp-150923131750-lva1-app6892/85/Introduction-to-Linked-Data-Platform-LDP-21-320.jpg)
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Introduction to Linked Data Platform (LDP)
- 1. Introduction to the Linked Data Platform (LDP) Hector Correa [email protected] The Pennsylvania State University
- 2. Agenda • What is the Linked Data Platform (LDP) • Basic definitions of concepts and rules • Examples • Why this is important • Q&A
- 3. Related Sessions • Linked data, URIs, and labels by Trey Terrel • Introducing Hydra-works: PCDM in Hydra by Lynette Rayle
- 4. Linked Data First introduced by Tim Berners-Lee in 2006 “The Semantic Web isn't just about putting data on the web. It is about making links, so that a person or machine can explore the web of data” – Identify things with valid URLs – Use standards for representation – Include other URLs in your data See http://www.w3.org/DesignIssues/LinkedData.html
- 6. Abraham_Lincoln label "Abraham Lincoln” . Abraham_Lincoln birthDate "1809-02-12” . Abraham_Lincoln profession "Lawyer” . [. . .] Abraham_Lincoln birthPlace Hodgenville,_Kentucky . http://dbpedia.org/data/Abraham_Lincoln.n3 Linked Data http://dbpedia.org/resource/Abraham_Lincoln http://dbpedia.org/resource/Hodgenville,_Kentucky
- 7. RDF 101 • Resource Description Framework http://www.w3.org/TR/rdf-primer/ • Data expressed in triples <subject> <predicate> <object> • For example <hydraconnect> <location> “Minneapolis” <hydraconnect> <date> “2015-09-22”
- 8. From read-only to read-write • How are we supposed to update Linked Data • Intuitively – use HTTP GET/POST – Resource Description Framework (RDF) • …but what are the mechanics, the rules, how do we deal with containership
- 9. Linked Data Platform (LDP) “defines a set of rules for HTTP operations on web resources, some based on RDF, to provide an architecture for read-write Linked Data on the web” http://www.w3.org/TR/ldp/ W3C Recommendation as of Feb/2015
- 10. Linked Data Platform (LDP) is an HTTP API for read-write Linked Data API stands for Application Programming Interface. An API defines the rules to communicate with a program.
- 11. LDP Client LDP Server HTTP GET Response (RDF or Non-RDF) HTTP POST (RDF or Non-RDF) Response Basic HTTP workflow
- 12. http://www.w3.org/TR/ldp/ • Everything is a Resource • RDF Sources: expressed in Resource Description Framework (triples) • Non-RDF Sources: everything else (web pages, PDFs, image/audio/video files, binaries, et cetera) Concepts Resource RDF Source Non-RDF Source
- 13. HTTP request POST localhost/ Slug: hydraconnect2015 <> dcterms:title “Hydra Connect 2015”. <> dcterms:subject “Hydra conference in Minneapolis”. HTTP response HTTP/1.1 201 Created Location: http://localhost/hydraconnect2015/ HTTP POST to create a new RDF Source (hydraconnect2015) Triples for the new resource Yup, created… …and here is the URL of the new resource Create a New RDF Source
- 14. Client makes HTTP request GET localhost/hydraconnect2015 Server returns HTTP response HTTP/1.1 200 OK Content-Type: text/turtle Link: <http://www.w3.org/ns/ldp#BasicContainer>; rel="type”, <http://www.w3.org/ns/ldp#Resource>; rel="type” <localhost/hydraconnect2015/> a ldp:BasicContainer ; dc:title “Hydra Connect 2015” ; dc:subject ““Hydra conference in Minneapolis” . HTTP GET request HTTPBody RDF source that is a container Fetch an Existing RDF Source HTTPHeaders
- 15. HTTP request POST localhost/ Slug: logo.jpg Content-Type: image/jpeg Content- Length: 1020 [binary of the image goes here] HTTP response HTTP/1.1 201 Created Location: http://localhost/logo.jpg HTTP POST to create a new Non-RDF Source Binary data …and here is the URL of the new resource Create a New Non-RDF Source
- 17. HTTP request POST localhost/hydraconnect2015/ Slug: session1 <> dcterms:title “Welcome to Hydra Connect 2015”. <> dcterms:subject “blah blah”. HTTP response HTTP/1.1 201 Created Location: http://localhost/hydraconnect2015/session1 POST to Basic Container Adding an RDF Source to a Basic Container (1/2)
- 18. HTTP request GET localhost/hydraconnect2015/ HTTP/1.1 HTTP response [the usual HTTP headers go here] <localhost/hydraconnect2015/> a ldp:BasicContainer ; dc:title “Hydra Connect 2015” ; dc:subject ““Hydra conference in Minneapolis” ; ldp:contains <localhost/hydraconnect2015/session1> . Fetch the Basic Container New triple automatically added by the LDP Server Adding an RDF Source to a Basic Container (2/2)
- 19. hydraconnect2015 session1 ldp:contains Welcome to Hydra Connect Hi Everybody Minneapolis September/2015 Basic Container Direct Container Added by LDP Client Added by LDP Server dc:title dc:title dc:subject dc:subject Legend Show me the Graph
- 20. HTTP request POST localhost/ HTTP/1.1 Slug: speakers <> dcterms:title “People that speakers at conferences”. <> rdf:DirectContainer . <> ldp:membershipResource <localhost/hydraconnect2015> . <> ldp:hasMemberRelation hasSpeaker . HTTP request POST localhost/speakers HTTP/1.1 Slug: janedev <> dcterms:title “Jane Developer”. Containership Direct Containers (1/2) Create Direct Container Add new resource to it
- 21. Direct Container (2/2) HTTP request GET localhost/hydraconnect2015 HTTP response [bunch of HTTP headers go here] <localhost/hydraconnect2015/> a ldp:BasicContainer ; dc:title “Hydra Connect 2015” ; dc:subject ““Hydra conference in Minneapolis” ; ldp:contains <localhost/hydraconnect2015/session1> ; hasSpeaker <localhost/speakers/janedev> . The membershipResource… …pointing to the new resource …has new triple with hasMemberRelation predicate
- 22. hydraconnect2015 session1 speakers janedev ldp:contains hasSpeaker ldp:contains ldp:membershipRelation Welcome to Hydra Connect Hi Everybody Jane Developer Minneapolis September/2015 Basic Container Direct Container Added by LDP Client Added by LDP Server People that speak at conferences dc:title dc:title dc:title dc:subject dc:subject Legend Show me the Graph hasSpeaker ldp:hasMemberRelation dc:title
- 23. Containers • “Containers are at the heart of LDP” – Robert Sanderson • Indirect Container you can link to a totally different resource than the one added • Direct and Indirect Containers you can revert the relationship (hasMemberRelation vs isMemberOfRelation) • Shameless plug: LDP Containers for the Perplexed http://tinyurl.com/ldp-containers • Read the W3C LDP Recommendation http://www.w3.org/TR/ldp/
- 24. Updates • Updates have not been standardized :( • The Linked Data Platform Working Group is currently favoring LD Patch but still is deciding. • Other candidates include SPARQL 1.1, SparqlPatch, TurtlePatch, and RDF Patch • As of July/2015, Linked Data Patch Format (LD Patch) is a note, not a recommendation • LD Patch http://www.w3.org/TR/2015/NOTE-ldpatch-20150728/
- 25. Why is LDP important to Hydra? • Fedora 4 is an LDP Server* • The Hydra Stack (i.e. your app) is an LDP Client – gems: LDP, ActiveTriples, ActiveFedora * Some restrictions apply
- 26. Thanks! Slides and notes available athttp://hectorcorrea.com/introduction-to-ldp