Semantic Pingback allows for interlinking between the document web and data web through a backwards compatible extension of the existing pingback mechanism. It supports RDFa-enhanced documents and typed links to enable propagation of semantic annotations without modifications. The approach defines requirements for pingback clients to detect pingback servers within semantic documents and communicate with them. Pingback servers are responsible for backlinking, provenance tracking, and spam prevention when processing requests. The technology has been implemented within the OntoWiki and Triplify systems and the pingback.aksw.org server.

1. Semantic Pingback
Sebastian Tramp Philipp Frischmuth Tim Ermilov Sören Auer
AKSW, Universität Leipzig
http://aksw.org/Projects/SemanticPingback

2. Introduction
Sussex St.
Reading Andrews NDL
Audio- Lists Resource subjects t4gm
MySpace scrobbler Lists
Moseley (DBTune) (DBTune) RAMEAU
Folk NTU SH lobid
GTAA Plymouth Resource
Lists
Organi-
Reading
Lists
sations
Music The Open ECS
Magna- Brainz Music
DB tune Library LCSH South-
(Data Brainz LIBRIS ampton
Tropes lobid Ulm
Incubator) (zitgist) Man- EPrints
Resources
chester
Surge Reading
biz. Music RISKS
Radio Lists The Open ECS
data. John Brainz
Discogs Library PSH Gem. UB South-
gov.uk Peel (DBTune)
FanHubz (Data In- (Talis) Norm- Mann- ampton
(DB cubator) Jamendo datei heim RESEX
Tune)
Popula- Poké- DEPLOY
Last.fm
tion (En- pédia
Artists Last.FM Linked RDF
AKTing) research EUTC (DBTune) (rdfize) LCCN VIAF Book Wiki
data.gov Produc- Pisa Eurécom
P20 Mashup semantic
NHS .uk tions classical web.org
(EnAKTing) Pokedex
(DB
Mortality Tune) PBAC ECS
(En-
AKTing)
BBC MARC (RKB Budapest
Program Codes Explorer)
Energy education OpenEI BBC List Semantic Lotico Revyu OAI
(En- CO2 data.gov mes Music Crunch SW
AKTing) (En- .uk Chronic- Linked Dog
NSZL Base
AKTing) ling Event- MDB RDF Food IRIT
America Media Catalog
ohloh
BBC DBLP ACM IBM
Good- BibBase
Ord- Wildlife
Recht- win (RKB
nance Openly Finder Explorer)
Local spraak. Family DBLP
legislation Survey Tele- New VIVO UF
.gov.uk nl graphis York flickr (L3S) New-
VIVO castle
Times URI wrappr Open Indiana RAE2001
UK Post- Burner Calais DBLP
codes statistics (FU
VIVO CiteSeer Roma
data.gov LOIUS Taxon iServe Berlin) IEEE
.uk Cornell
Concept Geo
World data
ESD Fact- OS dcs
Names book dotAC
stan- reference Project
Linked Data NASA (FUB) Freebase
dards data.gov Guten-
.uk
for Intervals (Data GESIS Course-
transport DBpedia berg STW ePrints CORDIS
Incu- ware
data.gov bator) (FUB)
Fishes ERA UN/
.uk
of Texas Geo LOCODE
Uberblic
Euro- Species
The stat dbpedia TCM SIDER Pub KISTI
(FUB) lite Gene STITCH Chem JISC
London Geo KEGG
DIT LAAS
Gazette TWC LOGD Linked Daily OBO Drug
Eurostat Data UMBEL lingvoj Med
(es) Disea-
YAGO Medi some
Care ChEBI KEGG NSF
Linked KEGG KEGG
Linked Drug Cpd
GovTrack rdfabout Glycan
Sensor Data CT Bank Pathway
US SEC Open Reactome
(Kno.e.sis) riese Uni
Cyc Lexvo Path-
way PDB Media
Semantic totl.net Pfam
HGNC
XBRL
WordNet KEGG KEGG Geographic
Linked Taxo- CAS Reaction
Twarql (VUA) UniProt Enzyme
rdfabout EUNIS Open nomy
US Census Publications
Numbers PRO- ProDom
SITE Chem2
UniRef Bio2RDF
Linking Open Data cloud diagram, by Richard Cyganiak and Anja Jentzsch.SGD
http://lod-cloud.net/ User-generated content
Climbing WordNet Homolo
Linked (W3C) Affy- Gene
GeoData
Cornetto
metrix Government
PubMed Gene
UniParc
Ontology
GeneID Cross-domain
Airports
Product
DB UniSTS MGI
Gen Life sciences
>200 interlinked datasets, >13 billion facts
Bank OMIM InterPro
As of September 2010

3. Blogosphere
• Distributed
• (Automated) Backlinking
• Trackback, Pingback
• Wordpress, Serendipity

4. Alice & Bob
Alice Link Bob
My thoughts What Alice
Notification
about... thinks of...
Original Post Responding Post
Comment + Backlink

5. Pingback
• Speci es:
• Simple communication interface
• Server detection mechanism
• Reactions and social interactions
• Result:
• Network effect
• Better interlinking

6. Semantic Pingback
• Support for
• Linked Data
• RDFa-enhanced
documents
• Mixed Pingbacks

7. Semantic Pingback (contd.)
Web of
Web of Data
Documents
Pingback Semantic Pingback

8. Requirements

9. Web of
Web of Data
Documents

10. Documents + Linked Data
<html>
<!-- ... -->
<a href="http://example.org/alice/post1">Link to Blogpost</a>
<!-- ... -->
</html>
# ...
<http://philipp.frischmuth24.de/id/me> a foaf:Person ;
foaf:name "Philipp Frischmuth" ;
foaf:knows <http://sebastian.tramp.name> ;
foaf:knows <http://id.feedface.de/me> .
# ...

11. Web of
Web of Data
Documents

12. Interlinking
Document and Data Web
• Links from Data Web:
• Conventional servers
• Semantic Pingbacks clients
• e.g. foaf:weblog

13. Web of
Web of Data
Documents

14. Interlinking (contd.)
Document and Data Web
• Links to Data Web:
• Conventional clients
• Semantic Pingback enabled servers
• e.g. link to DBpedia

15. Use RDFa-enhanced content
• Traditional blog and wiki systems + RDFa
• Plain links become typed links
• Propagation of typed links without further
modi cations

16. Server Announcement
within RDF documents
HTTP/1.1 302 Found
X-Pingback: http://pingback.aksw.org/
Location: http://bis.informatik.uni-leipzig.de/SebastianTramp
Content-Type: text/html
<html>
<!-- ... -->
<link rel="pingback" href="http://pingback.aksw.org" />
<!-- ... -->
</html>

17. Provenance Tracking
and Spam prevention
• Trust on the Data Web
• Track source of data
• Content analysis
• Social relationship

18. Architecture

19. Publisher
Linking Resource links Linked Resource
(Source) (Target)
announces
observes fetches (updates)
discovers (noti es)
Pingback Client communicates
Pingback Server
(Link Propagator)

20. Pingback Client
• Tasks:
(1) Determine suitable links
(2) Detect Pingback server
(3) Communicate with server
• Communication interface untouched

21. Server Detection
aka. autodiscovery process
HTTP/1.1 302 Found
X-Pingback: http://pingback.aksw.org/
Location: http://bis.informatik.uni-leipzig.de/SebastianTramp
Content-Type: text/html
• Applicable for all resource types
• Performs also with Linked Data

22. Server Detection (contd.)
<html>
<!-- ... -->
<link rel="pingback" href="http://pingback.aksw.org" />
<!-- ... -->
</html>
• Min. requirements on publisher side
• Applicable for HTML documents only
• Performs with RDFa-enhanced web pages

23. Server Detection (contd.)
@prefix pingback: <http://purl.org/net/pingback/> .
# ...
<http://philipp.frischmuth24.de/id/me> a foaf:Person ;
pingback:service <http://pingback.aksw.org/> ;
# ...
• Equivalent to HTML link element
• Usable in arbitrary RDF les

24. Pingback Server
• Communication behavior de ned only
• Guidelines for important tasks:
• Backlinking
• Provenance Tracking
• Spam prevention

25. Backlinking
3 steps:
(1) Request RDF representation
(2) Try to extract RDFa from HTML
(3) Search for untyped link(s)

26. Backlinking (contd.)
• Direct link(s): add to servers KB
• sioc:links_to or dc:references for
untyped links
• rdfs:seeAlso for links employing the
target resource as subject or object
• Optional: store metadata (e.g. description)

27. Provenance Tracking
• Provenance vocabulary by Hartig & Zhao
• Creation guideline for Pingback requests
• http://purl.org/net/pingback/RequestGuideline

28. Spam Prevention
• Valid links:
• Connecting source with target
• At least mentions target
• Admissible links:
• Information analysis
• Publisher relationship analysis

29. Implementation &
Evaluation

30. OntoWiki
Semantic (Data-)Wiki

31. Pingback in OntoWiki
Client & Server
• OntoWiki extension
• Client:
• On statement addition
• Subject: Linked Data enabled
• Object: Pingback-enabled

32. Pingback in OntoWiki (contd.)
Client & Server
• Server:
• Adds statements to local KB
• Versioning for provenance tracking

36. Triplify

37. Pingback in Triplify
# ...
<post/1> a sioc:Post ;
sioc:has_creator <user/1> ;
dcterms:created "2010-02-17T05:48:11" ;
dcterms:title "Hello world!" ;
sioc:content "Welcome to Wordpress. This is your..." .
# ...
<http://blog.aksw.org/2008/pingback-test/>
sioc:links_to <post/1> .

38. pingback.aksw.org
• Standalone Pingback server
• Can be employed for plain RDF les

39. pingback.aksw.org (contd.)
Try it out...!
<!-- ... -->
<foaf:Person rdf:about="http://philipp.frischmuth24.de/id/me">
<foaf:name>Philipp Frischmuth</foaf:name>
<foaf:based_near rdf:resource="http://dbpedia.org/resource/Leipzig" />
<foaf:knows rdf:resource="http://id.feedface.de/me" />
<foaf:knows rdf:resource="http://sebastian.tramp.name" />
<!-- ... -->
<pingback:service rdf:resource="http://pingback.aksw.org/" />
</foaf:Person>
<!-- ... -->

40. Conclusions
• Goals:
• Bring Pingback to the Data Web
• Interlink Document + Data Web
• Backwards compatible extension
• Easy to adapt

41. Thank You
• Demo Session
• Today, 4 - 6 pm, Room 2
• Anytime:
Norman Heino Sebastian Tramp Philipp Frischmuth