Simple Knowledge Organization System (SKOS) in the Context of Semantic Web Deployment, Library of Congress, May 2008


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Links are valuable. Links between documents, between people, between ideas, between data. Data is now a first class Web citizen, and the Web is expanding as more of these valuable networks are deployed within its fabric. Well-established knowledge organization systems like the Library of Congress Subject Headings will play a major role within these networks, as hubs, connecting people with information and providing a firm foundation for network growth as many new routes to the discovery of information emerge through the collective action of individuals. Or will they?

This talk introduces the Simple Knowledge Organization System (SKOS), a soon-to-be-completed W3C standard for publishing thesauri, classification schemes and subject headings as linked data in the Web. This talk also presents SKOS in the context of the W3C’s Semantic Web Activity, and in particular the work of the W3C’s Semantic Web Deployment Working Group where other specifications are being developed for publishing linked data in the Web, for embedding linked data in Web pages, and for managing Semantic Web vocabularies. Finally, this talk takes a mildly inquisitive look at the value propositions for linked data in the Web, and how LCSH might be deployed in the Web for better information discovery.

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  • Let me start by saying that I am here to promote SKOS. Having said that, I would like to be as objectives as I can about both the technical and the business arguments for using SKOS, and for buying in to the Semantic Web technology ecosystem. I’d like to do that because I’d like to use this presentation as a kind of sanity check. Libraries such as LOC who have invested over a long period of time in knowledge organisation have always been acknowledged as primary stakeholders in the development of SKOS, and SKOS has always been about providing a means for libraries to extract and to share more value from their knowledge organisation systems. So I’d very much like to know whether what I say today makes sense from your point of view. This is especially relevant as SKOS nears completion. The main technical work on SKOS will effectively be complete by the end of June.
  • Simple Knowledge Organization System (SKOS) in the Context of Semantic Web Deployment, Library of Congress, May 2008

    1. 1. The Simple Knowledge Organization System (SKOS) in the context of Semantic Web Deployment Alistair Miles Library of Congress May 2008
    3. 3. <ul><li>Testimony of Sir Timothy Berners-Lee CSAIL Decentralized Information Group Massachusetts Institute of Technology </li></ul><ul><li>Before the United States House of Representatives Committee on Energy and Commerce Subcommittee on Telecommunications and the Internet </li></ul><ul><li> </li></ul>
    4. 4. I. Foundations of the Web <ul><li>“ The success of the World Wide Web, itself built on the open Internet, has depended on three critical factors: </li></ul><ul><li>unlimited links from any part of the Web to any other; </li></ul><ul><li>open technical standards as the basis for continued growth of innovation applications; and </li></ul><ul><li>separation of network layers , enabling independent innovation for network transport, routing and information applications.” </li></ul>
    5. 5. A. Universal linking: Anyone can connect to anyone... <ul><li>“ In simple terms, the Web has grown because it's easy to write a Web page and easy to link to other pages.” </li></ul><ul><li>“ What makes it easy to create links ... is that there is no limit to the number of pages or number of links possible on the Web.” </li></ul><ul><li>“ Adding a Web page requires no coordination with any central authority , and has an extremely low, often zero, additional cost.” </li></ul>
    6. 6. <ul><li>“ Adding a page provides content, but adding a link provide the organization, structure and endorsement to information on the Web which turn the content as a whole into something of great value.” </li></ul>
    7. 7. <ul><li>“ The universality and flexibility of the Web's linking architecture has a unique capacity to break down boundaries of distance, language, and domains of knowledge.” </li></ul><ul><li>“ These traditional barriers fall away because the cost and complexity of a link is unaffected by most boundaries that divide other media.” </li></ul>
    8. 8. <ul><li>“ The Web's ability to allow people to forge links is why we refer to it as an abstract information space , rather than simply a network.” </li></ul>
    9. 9. II. Looking forward <ul><li>“ First, the Web will get better and better at helping us to manage, integrate, and analyze data .” </li></ul><ul><li>“ Today, the Web is quite effective at helping us to publish and discover documents, but the individual information elements within those documents ... cannot be handled directly as data.” </li></ul>
    10. 10. <ul><li>“ Today you can see the data with your browser, but can't get other computer programs to manipulate or analyze it without going through a lot of manual effort yourself.” </li></ul><ul><li>“ As this problem is solved, we can expect that Web as a whole to look more like a large database or spreadsheet , rather than just a set of linked documents.” </li></ul>
    11. 11. A. Data Integration <ul><li>“ Locked within all of this data is the key to knowledge about how to cure diseases, create business value, and govern our world more effectively.” </li></ul><ul><li>“ The good news is that a number of technical innovations... </li></ul><ul><li>... (RDF which is to data what HTML is to documents, and the Web Ontology Language (OWL) which allows us to express how data sources connect together) ... </li></ul><ul><li>... along with more openness in information sharing practices are moving the World Wide Web toward what we call the Semantic Web .” </li></ul>
    12. 12. <ul><li>“ Progress toward better data integration will happen through use of the key piece of technology that made the World Wide Web so successful: the link .” </li></ul><ul><li>“ The power of the Web today, including the ability to find the pages we're looking for , derives from the fact that documents are put on the Web in standard form, and then linked together .” </li></ul>
    13. 13. <ul><li>“ The Semantic Web will enable better data integration by allowing everyone who puts individual items of data on the Web to link them with other pieces of data using standard formats.” </li></ul>
    15. 15.
    16. 16. FlyWeb Project <ul><li>Fruit flies ( Drosophila ...) </li></ul><ul><li>Model organism </li></ul><ul><li>Extensive body of genetic research </li></ul><ul><li>Much of that knowledge is in journal papers </li></ul><ul><li>Recognised value of research data </li></ul><ul><li>Establish public databases </li></ul><ul><ul><li>E.g. FlyBase </li></ul></ul><ul><ul><li>Centrally curated </li></ul></ul>
    17. 17.
    18. 18. Data Webs <ul><li>Link data resources </li></ul><ul><li>Ask questions that no single data resource can answer </li></ul><ul><li>What’s the easiest, cheapest, most scalable way to achieve this? </li></ul><ul><li>Agile approach, add value incrementally, return value early and often... </li></ul>
    19. 19. Vertical Web Apps Level 0 – Any Data Resources in the Web Level 1 – SPARQL End-points Level 2 – SPARQL End-points (Schema Alignment) Level 3 – SPARQL End-points (Integrated Data) Web 2 Mash-ups SPARQL Mash-ups SPARQL Mash-ups ??? Data Web Layer Cake
    20. 20. Example Application <ul><li>[insert screenshot of mashup] </li></ul>
    21. 21. Future, self-publishing <ul><li>As publishing data on the Web becomes easier... </li></ul><ul><li>...more research groups will publish their own data... </li></ul><ul><li> network of data resources... </li></ul><ul><li>...challenging traditional view of scholarly life cycle & value chain ... value grid... </li></ul>
    22. 22. SKOS
    23. 23. Potted History <ul><li>SKOS 2001 (pre-alpha) </li></ul><ul><ul><li>Thesaurus Interchange Format (TIF), LIMBER Project </li></ul></ul><ul><li>SKOS 2003 (alpha) </li></ul><ul><ul><li>Semantic Web Advanced Development for Europe (SWAD-Europe) </li></ul></ul><ul><li>SKOS 2005 (beta) </li></ul><ul><ul><li>W3C Semantic Web Best Practices and Deployment Working Group (SWBPD) </li></ul></ul><ul><li>SKOS 2008 (W3C Recommendation) </li></ul><ul><ul><li>W3C Semantic Web Deployment Working Group (SWD) </li></ul></ul>
    24. 24.
    25. 25. Layers in the Web <ul><li> </li></ul><ul><li>Third layer is network (graph) of connections beyond documents... </li></ul><ul><li>... people, organisations, genes, proteins, concepts ... </li></ul><ul><li>Represent these connections (data) in the (Semantic) Web </li></ul>
    26. 26. KOS e.g. LCSH <ul><li>Can be viewed as a network of interconnected concepts </li></ul><ul><li>Represent LCSH as data in the Web </li></ul><ul><ul><li>Make those concepts and their interconnections part of the Web </li></ul></ul>
    27. 27.
    28. 28.
    29. 29.
    30. 30.
    31. 31. Publishing KOS in the Web? <ul><li>Use RDF </li></ul><ul><ul><li>Basic framework for data in the Web – resources, literals, links... (“graphs” of data) </li></ul></ul>
    32. 32. Publishing KOS in the Web? <ul><li>Use SKOS </li></ul><ul><li>Standard set of... </li></ul><ul><ul><li>Resource types (Classes) </li></ul></ul><ul><ul><li>Link types (Properties) </li></ul></ul><ul><li>... For representing KOS as RDF data </li></ul><ul><li>(N.B. Because use URIS as names for classes and properties, call this an RDF vocabulary) </li></ul>
    33. 33. SKOS Resource Types (Classes) <ul><li>skos:Concept </li></ul><ul><ul><li>E.g. Baseball in art </li></ul></ul><ul><li>skos:ConceptScheme </li></ul><ul><ul><li>E.g. LCSH itself </li></ul></ul>
    34. 34. SKOS Link Types (Properties) <ul><li>For labeling concepts </li></ul><ul><ul><li>skos:prefLabel, skos:altLabel, skos:hiddenLabel </li></ul></ul><ul><li>For documenting concepts </li></ul><ul><ul><li>skos:note, skos:scopeNote, skos:definition, skos:editorialNote... </li></ul></ul><ul><li>For linking concepts </li></ul><ul><ul><li>skos:broader, skos:narrower, skos:related </li></ul></ul>
    35. 35. <ul><li> </li></ul>
    36. 36.
    37. 37.
    38. 38. Publishing LCSH in the Web <ul><li>Project LCSH into RDF (i.e. create an RDF representation) </li></ul><ul><li>Publish it in the Web as linked data </li></ul><ul><ul><li> </li></ul></ul><ul><li>Ed Summers, Clay Redding, Dan Krech, Antoine Isaac </li></ul>
    39. 39. Scope of SKOS <ul><li>SKOS will be an all-encompassing standard for the lossless representation and exchange of all varieties of knowledge organisation system ... ? </li></ul><ul><ul><li>No </li></ul></ul><ul><li> -- Antoine Isaac </li></ul>
    40. 40. <ul><li>“ ...the things that we aim at representing are very diverse: some classification schemes use ‘codes’ and refer to ‘classes’, thesauri have ‘terms’ and so on.” </li></ul>
    41. 41. <ul><li>“ Yet, it happens, looking at the way these things are used now and will be in the near future (with more and more links established between them), that (i) some standardisation has to take place, and that (ii) this standardisation can be actually grounded on some observed practical similarities ( )” </li></ul><ul><li>“ Our aim is not to replace the original objects in their initial context of use, but to allow to port them to a shared space , based on a simplified model , enabling wider re-use and better interoperability.” </li></ul>
    42. 42. Lessons from the Web <ul><li>Less is more ... </li></ul><ul><ul><li>E.g. REST over SOAP </li></ul></ul><ul><li>SKOS should capture a small amount of common ground ... Just enough to enable KOS’s valuable concepts and connections to be deployed in the Web and be linked to/from </li></ul><ul><li>N.B. SKOS is infinitely extensible! </li></ul><ul><ul><li>Easy to mix & match </li></ul></ul><ul><ul><li>Easy to refine </li></ul></ul>
    43. 43. THE VALUE OF LINKS
    44. 44. The value of links <ul><li>The Web showed, links between documents are really useful </li></ul><ul><li>Google’s pagerank showed, structure of network means something (and is worth something!) </li></ul><ul><li>Social networking Web sites showed, how much we value other kinds of links </li></ul>
    45. 45. Linked Metadata <ul><li>You’ve got LCSH in the Web, what next? </li></ul><ul><li>... Linked metadata...? </li></ul>
    46. 46. <ul><li> </li></ul>
    47. 47.
    48. 48.
    49. 49. <ul><li>[insert demo, show how links change topology of information space] </li></ul>
    50. 50.
    51. 51. Value Proposition <ul><li>Links are paths to the discovery of information </li></ul><ul><li>Links can be exploited in useful (and surprising) ways </li></ul><ul><li>Well-established KOS like LCSH can be hubs in the network of linked metadata, bridging ... </li></ul><ul><li>(On the Semantic Web, LCSH should get very high semantic pagerank !) </li></ul>
    52. 52. USING URIS
    53. 53. Why use URIs? <ul><li>Identifier management </li></ul><ul><li>Data discovery </li></ul>
    54. 54. Identifier management <ul><li>Referring to things </li></ul><ul><li>In a database, each table has a primary key </li></ul><ul><li>What happens when you try to combine data from 2 databases? </li></ul><ul><ul><li>Identifier clashes (ambiguous reference) </li></ul></ul><ul><ul><li>Identifier aliases (co-reference) </li></ul></ul><ul><li>Clashes hurt precision, give you nonsense </li></ul><ul><li>Aliases hurt recall, miss important results/links </li></ul>
    55. 55. URIs & identifier management <ul><li>URIs are like a single, global pool of identifiers – one world-wide primary key </li></ul><ul><li>Can claim ownership of parts of “URI space” </li></ul><ul><li>Even though we’re all using same primary key, mechanism for avoiding URI clashes </li></ul><ul><li>Can join data from multiple sources with confidence </li></ul><ul><li>But ... doesn’t solve the alias problem, still need to find co-references </li></ul>
    56. 56. Data discovery <ul><li>Problem with distributed data ... How do you find everything thats “out there”? </li></ul><ul><li>Two general approaches: </li></ul><ul><ul><li>Centralised </li></ul></ul><ul><ul><li>Decentralised </li></ul></ul>
    57. 57. Centralised discovery <ul><li>Someone somewhere keeps a “catalogue” of everything </li></ul><ul><li>Everyone “knows” where that catalogue is </li></ul><ul><li>New sources “tell” the catalogue about themselves (a.k.a. “register” themselves) </li></ul><ul><li>E.g. Gas maintenance </li></ul><ul><li>Works well at small-medium scales </li></ul><ul><ul><li>E.g. FlyWeb </li></ul></ul><ul><li>Rely on networks outside the Web (e.g. Knowing the right people) </li></ul>
    58. 58. FlyWeb Project <ul><li>[small number of large data resources] </li></ul>
    59. 59. Decentralised discovery <ul><li>Data in one source refers data in another (using a URI) </li></ul><ul><li>Data from the other source can be retrieved directly, by “de-referencing” the URI via the Web </li></ul><ul><li>So given one data source, you can “follow your nose” and retrieve data from all linked sources ... </li></ul><ul><li>... without needing a central catalogue or registry, just the Web </li></ul><ul><li>Works well up to Web-scale </li></ul><ul><ul><li>E.g. FOAF </li></ul></ul>
    60. 60. Dereferenceable? <ul><li>For some URIs, can retrieve a “representation” of the “resource” via the Web </li></ul><ul><li>(N.B. “resource” = “thing”) </li></ul>
    61. 61. FOAF <ul><li>Very large number of relatively small data resources </li></ul>
    62. 62. Why use URIs? <ul><li>Identity management </li></ul><ul><ul><li>From 2 to 2 billion data sources, always a problem </li></ul></ul><ul><li>Data discovery </li></ul><ul><ul><li>Ability to “de-reference” a URI opens possibility for decentralisation </li></ul></ul><ul><ul><li>Ability to “de-reference” is also useful in centralised models (e.g. Registries can harvest) </li></ul></ul>
    64. 64. W3C SWD WG <ul><li>SKOS </li></ul><ul><li>RDFa </li></ul><ul><li>Recipes for publishing RDF (linked data) </li></ul><ul><li>Vocabulary management </li></ul>
    65. 65. W3C Semantic Web Activity <ul><li>Semantic Web Deployment </li></ul><ul><li>Data Access (DAWG) </li></ul><ul><ul><li>SPARQL query language, SPARQL protocol </li></ul></ul><ul><li>GRDDL </li></ul><ul><li>OWL 2 </li></ul><ul><li>SWHCLSIG </li></ul><ul><li>SWEO </li></ul>
    66. 66. SUMMARY
    67. 67. Suggestions <ul><li>Linked KOS </li></ul><ul><ul><li>Project LCSH into RDF (SKOS) – done </li></ul></ul><ul><ul><li>Publish LCSH as linked data in the Web – done </li></ul></ul><ul><ul><li>Publish SPARQL endpoint for LCSH </li></ul></ul><ul><li>Linked metadata </li></ul><ul><ul><li>Project LOC metadata into RDF </li></ul></ul><ul><ul><li>Publish LOC metadata as linked data in the Web </li></ul></ul><ul><ul><ul><li>With links to LCSH & LCC </li></ul></ul></ul><ul><ul><li>Publish SPARQL endpoint for LOC metadata </li></ul></ul>
    68. 68. Bibliographic Information as RDF? <ul><li>Projecting LCSH into RDF ... SKOS is standard vocabulary of resource & link types </li></ul><ul><li>Projecting LCSH metadata into RDF ... Which vocabulary to use??? </li></ul><ul><li>Challenge – diversity of bibliographic information! </li></ul>
    69. 69. RDA -> RDF <ul><li>Joint DCMI/RDA task force </li></ul><ul><li>Seed funding to develop initial prototype RDF vocabularies for bibliographic information </li></ul><ul><li>Based on FRBR and data model implicit in RDA </li></ul><ul><li>Early stages </li></ul><ul><li> </li></ul><ul><li>Karen Coyle </li></ul>
    70. 70. Thanks <ul><li>STFC Rutherford Appleton Lab </li></ul><ul><ul><li>Brian Matthews, Michael Wilson, Juan Bicarregui </li></ul></ul><ul><li>Oxford Image Bioinformatics Research Group </li></ul><ul><ul><li>David Shotton, Graham Klyne, Jun Zhao </li></ul></ul><ul><li>W3C Semantic Web Deployment WG </li></ul><ul><li>Members of [email_address] </li></ul><ul><li>Comments on SKOS -> [email_address] </li></ul>