Introduction to APIs and Linked Data
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Talk given at Open Knowledge Foundation 'Opening Up Metadata: Challenges, Standards and Tools' Workshop, Queen Mary University of London, 13th June 2012. Info on the event at http://openglam.org/2012/05/31/last-places-left-for-opening-up-metadata-challenges-standards-and-tools/
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Introduction to APIs and Linked Data
- 1. Introduction to APIs and Linked Data Adrian Stevenson Senior Technical Innovations Coordinator Mimas, University of Manchester, UK @adrianstevenson
- 2. Benefits of APIs for GLAMs • Cross-searching • Improved resource discovery • Data not trapped in silos • Findability on the Web – Google • Data re-use • Bringing data together - integration • Enhanced services – e.g. Mashups 2
- 3. Metadata • What is it? - Data about data • How do you create it? – Catalog card, text editor, Word, Excel, Access, XML Editor…. • Do you use standards? – EAD – Encoded Archival Description – Not using standards may have implications for interoperability & sustainability • How do you move it around? – CDs, Email attachments, FTP, APIs 3
- 4. What is an API? • „Application Programming Interface‟ – “API is an online interface that allows distributed systems to communicate with one another and exchange information” – “APIs are carefully thought out pieces of code created by programmers .. that allow other applications to interact with their application” 4
- 5. APIs • Allow machine readability of data – Typically over the Web • Provide other systems with access to content or functions • Many types – e.g. – Google, Facebook, Flickr, twitter APIs …. – OAI-PMH – Linked Data API, SPARQL – Others include SOLR, SRU, Z39.50, SOAP, …. 5
- 6. APIs are Machine to Machine • API is software-to-software interface, not a user interface • E.g. Cinema ticket websites use API: – Sends credit card info to remote application – Remote application sends response back to ticket website saying OK to issue the tickets • User see one interface 6
- 7. Historypin 7 http://www.historypin.com
- 8. Mashups 8 Data from www.openimages.eu/api http://www.vistory.nl/
- 9. 9
- 10. Twitter API 10 https://dev.twitter.com/
- 12. Open Expenses 12 http://benosteen.wordpress.com/2010/02/27/giving-the-mps-a-receipt-for-their-expenses-claim/
- 13. OAI-PMH • Open Archive Initiative Protocol for Metadata Harvesting • Mechanism for repositories and services to share metadata over the Web • Facilitates cross-searching • Works by use of 6 „verbs‟ – E.g. ListMetadataFormats, ListRecord, GetRecord … – http://archiveshub.ac.uk/api/OAI-PMH/2.0/hub?verb=Identify – http://archiveshub.ac.uk/api/OAI- PMH/2.0/hub?verb=GetRecord&identifier=gb141vbh&metadataPrefix=o ai_dc 13
- 14. OAI-PMH: GetRecord 14
- 16. Linked Data “The term Linked Data refers to a set of best practices for publishing and connecting structured data on the Web.” “the Semantic Web is the goal or end result… Linked Data provides the means to reach that goal” From „Linked Data: The Story So Far‟ - Heath, Bizer and Berners-Lee 2009 16
- 17. The goal of Linked Data is to enable people to share structured data on the Web as easily as they can share documents today. Bizer/Cyganiak/Heath Linked Data Tutorial, linkeddata.org
- 18. Linked Data Design Issues • URIs • LD Design Issues • Triples http://www.w3.org/DesignIssues/LinkedData.html
- 19. URIs and HTTP • “A Uniform Resource Identifier’ (URI) provides a simple and extensible means for identifying a resource” – W3C RFC 3986 • HTTP URIs may be „de-referenced‟on the Web • HTTP URIs are used for “real world” things • http://adrianstevenson.com/id/me • http://dbpedia.org/resource/Love
- 20. RDF • Resource Description Framework – a language for representing information about resources on the Web – RDF can be used to represent things identified on the Web, even when they cannot be directly retrieved on the Web • Describes relations using „triples‟ • http://www.w3.org/TR/REC-rdf-syntax/
- 21. Triples • Triples statements – „Things‟ have „properties‟ with „values‟ – Subject – Predicate - Object Keith Richards Is Member Of The Rolling Stones Repository Provides Access To Archival Resource • Triples are the basis of RDF and Linked Data
- 23. From RDF to Linked Data • If something is identified, it can be linked to • We take items from our datasets and link them to items from other datasets BBC Copac VIAF DBPedia GeoNames Archives Hub
- 29. Key Benefit of Linked Data • Web 2.0 mashups work against a fixed set of data sources • Hand crafted by humans • Don‟t integrate well • Linked Data promises an unbound global data space • Easy dataset integration • Generic „mesh-up‟ tools
- 30. Benefits for GLAMs • Cross-searching • Improved resource discovery • Data not trapped in silos • Findability on the Web – Google • Data re-use • Bringing data together - integration • Enhanced services 32
- 31. Linked Data Challenges • Dirty data, URI persistence • Steep learning curve • Complexity • How sustainable are the data sources? • How scalable are triple stores? • Can you track the provenance of data sources? • Licensing 33
- 32. Contact Adrian Stevenson Mimas, University of Manchester, UK [email protected] www.mimas.ac.uk @adrianstevenson www.linkedin.com/in/adrianstevenson www.slideshare.net/adrianstevenson 34
- 33. CC License • This presentation available under creative commons Non Commercial-Share Alike: http://creativecommons.org/licenses/by-nc/2.0/uk/
Editor's Notes
- #4: EAD is XML format based on ISAD(G) rules
- #5: Emphasise interfaceInterface is a common boundary between separate systemsAPIs are specially crafted to expose only chosen functionality and/or data while safeguarding other parts of the application which provides the interface.
- #6: Some have more of an interoperability focus, some more proprietary.
- #9: What are APIs good for? – One things is mashupsUsesOpenBeeldenie. Open Images http://www.openimages.eu/api/ which is OAI-PMH and GPS dataAllows you to merge your snapshots at locations with snapshots from historical films – Augemented reality in reverse.Looks a bit like Historypin
- #10: Pronounced ‘Rikesmonumenten’ which is the National Heritage Museum(location-based) information on Holland’s 61,000 heritage sites
- #11: How do you use APIs – documentation and some dev skills.
- #14: It’s a harvesting approachEmphasise machine readabilityServices have OAI-PMH intefaces that facilitate harversting by data. Data can be put into repository to allow cross searching and distributed searching
- #18: Has been described as a ‘data commons’, or more usually a Web of Data.
- #19: Step back a bit to HTMLHTML web of documents doesn’t encourage re-use, reduce redundancy. Are network effects but could be much better.
- #20: Note this is a considerable simplification of the detail in danger of misleading.Linked data exploits semantically meaningful tagging to encourage re-use, reduce redundancy etc.
- #21: http://www.w3.org/DesignIssues/LinkedData.html
- #23: Uses predicate logic. Goes back to Aristotle.Conceptualises things, and the relationships between things
- #26: In hypertext web sites it is considered generally rather bad etiquette not to link to related external material. The value of your own information is very much a function of what it links to, as well as the inherent value of the information within the web page. So it is also in the Semantic Web.Remember, this is about machines linking – machines need identifiers; humans generally know when something is a place or when it is a person. BBC + DBPedia + GeoNames + Archives Hub + Copac + VIAF = the Web as an exploratory spaceUsers very interested in related materials acc to Terry Catapano at SAA 2011. LD can really help with this.
- #27: Can get XSLT stylesheet here too!
- #28: Note that it is machine readable interface as well as the human interfaceCurrently have a few hundred in Locah. There are 25,000 EAD records on theHub srevice. We’re Intending to put about 2,000 up for Linking Lives Project.
- #31: ‘Every story has a beginning’Nice example of consumption of Archives Hub linked data
- #32: Data can be integrated from many diff sourcesUsers very interested in related materials acc to Terry Catapano at SAA 2011. LD can really help with this.