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Linked Data and Locah, UKSG2011
 

Linked Data and Locah, UKSG2011

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An introduction to Linked Data and to the Linked Open Copac and Archives Hub project.

An introduction to Linked Data and to the Linked Open Copac and Archives Hub project.

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  • Has been described as a ‘data commons’, or more usually a Web of Data.
  • Problem for machines to extract meaning. At present, the raw data is not really available.
  • Persitent URIs for names of things – http URIs are names, not addressesProvide information – properties and classes for a URIMore links
  • Things are resources because someone created a URI to identify them, not because they have some particular properties in and of themselves.HTTP URIs provide a simple way to create globally unique names without centralized management; and URIs work not just as a name but also as a means of accessing information about a resource over the Web
  • In a data graph, there is no concept of roots (or a hierarchy). A graph consists of resources related to other resources, with no single resource having any particular intrinsic importance over another.
  • This subject – the archive itself – has a page (foaf:page being the property) with name ‘finding aid’. The ‘finding aid’ is the object of this statement, but is also itself a subject. A subject in an RDF document may also be referenced as an object of a property in another RDF statement.
  • We have four ‘things’ here: unit of description; repostiory; finding aid; EAD document. We have given Unit of description a number of properties. Other things can also have properties (this is simplified)These properties are indicated in the green boxes. They are also called predicates.
  • 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 space
  • Once you say that they are the same, the implication is that they share the same classes and properties.
  • Ontology defines a ‘knowledge domain’
  • Encoded Archival Description is an XML standard for encoding archival finding aidsThe Object Description Schema (MODS) is an XML-based bibliographic description schemaMODS - Metadata Object Description Schema (MODS) is a schema for a bibliographic element set that may be used for a variety of purposes, and particularly for library applications.EAD - Things” include concepts and abstractions as well as material objects We want location – archives physical things so location importantAlso wanted event data, partly steered by the visualisation prototypeAlso ‘extent’ data – number of boxes
  • 303 and Content Neg from ‘Cool URIs for the Semantic Web’
  • Open Data Commons Public Domain DedicationCreative Commons CC0 license
  • e.g. index terms may not always apply down the hierarchy of the descriptionWe are pulling down into lower-level descriptions

Linked Data and Locah, UKSG2011 Linked Data and Locah, UKSG2011 Presentation Transcript

  • How to Become a First Class Citizen of the Web
    Linked Data and the LOCAH project
    Jane Stevenson & Adrian Stevenson
  • Remit
    This session will give a brief overview of the concepts behind Linked Data and will explain how we are applying these ideas to archival and bibliographic data.
    Archives Hub: merged catalogue of archival descriptions from 200 institutions across the UK
    Copac: merged catalogue of bibliographic records from libraries across the UK
  • Introduction
  • The goal of Linked Data is to enable people to share structured data on the Web as easily as they can share documents today.
    [The creation of] a space where people and organizations can post and consume data about anything.
    Bizer/Cyganiak/Heath Linked Data Tuturial, linkeddata.org
  • In essence, it marks a shift in thinking from publishing data in human readable HTML documents to machine readable documents. That means that machines can do a little more of the thinking work for us.
    http://www.linkeddatatools.com/semantic-web-basics
  • Linked Data encourages open data, open licences and reuse.
    …but Linked Data does not have to be open.
  • Core questions
    Is it achievable?
    Will it bring substantial benefits?
    “It is the unexpected re-use of information which is the value added by the web”
  • What is Linked Data?
    4 ‘rules’ of for the web of data:
    Use URIs as names for things
    Use HTTP URIs so that people can look up those names.
    When someone looks up a URI, provide useful information, using the standards (RDF, SPARQL)
    Include links to other URIs. so that they can discover more things.
    http://www.w3.org/DesignIssues/LinkedData.html
  • Giving Things identifiers
    We can make statements about things and establish relationships by assigning identifiers to them.
    Jane Stevenson = http://archiveshub.ac.uk/janefoaf.rdf
    Manchester = http://dbpedia.org/resource/manchester
    English = http://lexvo.org/id/iso639-3/eng
  • URIs
    Uniform Resource Identifiers (URIs) are identifiers for entities (people, places, subjects, records, institutions).
    They identify resources, and ideally allow you to access representations of those resources.
    Think not of locations, but of identifiers!
    For Linked Data you use HTTP URIs
    Jane Stevenson = http://archiveshub.ac.uk/janefoaf.rdf
    Manchester = http://dbpedia.org/resource/manchester
    English = http://lexvo.org/id/iso639-3/eng
  • Entities and Relationships
  • Triple statement
    AccessProvidedBy
    Archival Resource
    Repository
    ProvidesAccessTo
    Subject: Archival Resource
    Predicate: AccessProvidedBy
    Object: Repository
    Subject > Predicate > Object
  • HTTP URIs
    ArchivalResource: http://data.archiveshub.ac.uk/id/findingaid/gb-106-7esp
    <accessProvidedBy>
    Repository: http://data.archiveshub.ac.uk/id/repository/gb106
    Archival Resource
    Repository
    accessProvidedBy
  • An RDF Graph
    Title
    has
    Archival Resource
    Repository
    heldAt
    describedBy
    encodedAs
    Finding Aid
    EAD document
  • So...?
    If something is identified, it can be linked to
    We can then take items from one dataset and link them to items from other datasets
    BBC
    Copac
    VIAF
    DBPedia
    GeoNames
    Archives Hub
  • The Linking benefits of Linked Data
    BBC:Cranford
    Copac:Cranford
    VIAF:Dickens
    DBPedia: Gaskell
    Hub:Gaskell
    Geonames:Manchester
    DBPedia: Dickens
    Hub:Dickens
  • The Web of ‘Documents’
    Global information space (for humans)
    Document paradigm
    Hyperlinks
    Search engines index and infering relevance
    Implicit relationships between documents
    Lack of semantics
  • The Web of Linked Data
    Global data space (for humans and machines)
    Making connections between entities across domains (people, books, films, music, genes, medicines, health, statistics...)
    LD is not about searching for specific documents or visiting particular websites, it is about things - identifying and connecting them.
    Closely aligned to the general architecture of the Web
  • From one thing…to the same thing
    <sameAs>
    http://dbpedia.org/resource/manchester
    http://sws.geonames.org/2643123
    http://data.archiveshub.ac.uk/id/concept/ncarules/manchester
    Are they the same?
  • Vocabularies & Ontologies
  • Vocabularies & Ontologies
    Vocabulary: set of terms
    Ontology: organisation of terms – hierarchy, relationships
  • Shared vocabularies
    Problems of data integration: information exchange across independently designed systems
    Two different databases: one for films one for actors
    To collaborate using their current databases, the owners of either site would have to decide on a common data format by which to share information that they could both understand by using a common film and actor unique ID scheme of their own invention.
  • Need ‘film title’; ‘actor name’; ‘actor birthdate’, etc. to mean the same thing to each
    Use the same vocabulary
    Query both databases.
    No need for transformations, mappings, contracts
  • Vocabularies in Linked Data
    Common vocabulary to describe the data, e.g. ‘film-title’ means the same thing
    Adopt the same ontologies for expressing meaning
    Use semantics to link data
    Want to avoid transformation, mapping, contracts between data providers
  • Shared use of vocabularies
    DC
    DC
    Copac
    Hub
    Hub RDF
    Copac RDF
    foaf
    bibo
    foaf
    skos
    skos
    dcterms:title
    dcterms:identifier
  • Ontologies
    Many widely used ontologies
    Use others as far as possible
    Use your own where necessary
    Dublin Core
    Friend of a Friend (FOAF)
    Simple Knowledge Organisation System (SKOS)
    Bibo
    Open Cyc
  • Linked Data on the Hub & Copac
    Linked Open Copac and Archives Hub: Locah
    JISC funded project
    August 2010 – July 2011
    Mimas
    UKOLN
    Eduserv
  • What is LOCAH doing?
    Part 1: Exposing the Linked Data
    Part 2: Creating a prototype visualisation
    Part 3: Reporting on opportunities and barriers
  • How are we exposing the Data?
    Model our ‘things’ into RDF
    Transform the existing data into RDF/XML
    Enhance the data
    Load the RDF/XML into a triple store
    Create Linked Data Views
    Document the process, opportunities and barriers on LOCAH Blog
  • 1. Modelling ‘things’ into RDF
    Hub data in ‘Encoded Archival Description’ EAD XML form
    Copac data in ‘Metadata Object Description Schema’ MODS XML form
    Take a step back from the data format
    Think about your ‘things’
    What is EAD document “saying” about “things in the world”?
    What questions do we want to answer about those “things”?
    http://www.loc.gov/ead/ http://www.loc.gov/standards/mods/
  • 1. Modelling ‘things’ into RDF
    Need to decide on patterns for URIs we generate
    Following guidance from W3C ‘Cool URIs for the Semantic Web’ and UK Cabinet Office ‘Designing URI Sets for the UK Public Sector’
    http://data.archiveshub.ac.uk/id/findingaid/gb1086skinner ‘thing’ URI
    … is HTTP 303 ‘See Other’ redirected to …
    http://data.archiveshub.ac.uk/doc/findingaid/gb1086skinner document URI
    … which is then content negotiated to …
    http://data.archiveshub.ac.uk/doc/findingaid/gb1086skinner.htmlhttp://data.archiveshub.ac.uk/doc/findingaid/gb1086skinner.rdf http://data.archiveshub.ac.uk/doc/findingaid/gb1086skinner.turtlehttp://data.archiveshub.ac.uk/doc/findingaid/gb1086skinner.json
    http://www.w3.org/TR/cooluris/http://www.cabinetoffice.gov.uk/resource-library/designing-uri-sets-uk-public-sector
  • 1. Modelling ‘things’ into RDF
    Using existing RDF vocabularies:
    DC, SKOS, FOAF, BIBO, WGS84 Geo, Lexvo, ORE, LODE, Event and Time Ontologies
    Define additional RDF terms where required,
    hub:ArchivalResource
    copac:BibiographicResource
    hub:maintenanceAgency
    copac:Creator
    It can be hard to know where to look for vocabs and ontologies
    Decide on licence – CC BY-NC 2.0, CC0, ODC PDD
  • Archives Hub Model (as at 14/2/2011)
    in
    Finding Aid
    Place
    PostcodeUnit
    Repository(Agent)
    administeredBy/administers
    maintainedBy/maintains
    encodedAs/encodes
    hasPart/partOf
    EAD Document
    accessProvidedBy/providesAccessTo
    Level
    Biographical History
    topic/page
    hasBiogHist/isBiogHistFor
    Language
    level
    ArchivalResource
    language
    at time
    topic/page
    origination
    hasPart/partOf
    TemporalEntity
    Creation
    product of
    associatedWith
    extent
    inScheme
    Extent
    Concept
    ConceptScheme
    Agent
    representedBy
    Object
    foaf:focus
    Is-a
    Is-a
    associatedWith
    Family
    Person
    Organisation
    Place
    Book
    participates in
    Genre
    Function
    Birth
    Death
    TemporalEntity
    at time
  • Copac Model (as at November 2010)
  • Feedback Requested!
    We would like feedback on the model
    Appreciate this will be easier when the data available
    Via blog
    http://blogs.ukoln.ac.uk/locah/2010/09/28/model-a-first-cut/
    http://blogs.ukoln.ac.uk/locah/2010/11/08/some-more-things-some-extensions-to-the-hub-model/
    http://blogs.ukoln.ac.uk/locah/2010/10/07/modelling-copac-data/
    Via email, twitter, in person
  • 2. Transforming in RDF/XML
    Transform EAD and MODS to RDF/XML based on our models
    Hub: created XSLT Stylesheet and used Saxon parser
    http://saxon.sourceforge.net/
    Saxon runs the XSLT against a set of EAD files and creates a set of RDF/XML files
    Copac: created in-house Java transformation program
  • 3. Enhancing our data
    Language - lexvo.org
    Time periods - reference.data.gov.uk
    Geolocation - UK Postcodes URIs and Ordnance Survey URIs
    Names - Virtual International Authority File
    Matches and links widely-used authority files - http://viaf.org/
    Names (and subjects) - DBPedia
    Subjects - Library of Congress Subject Headings
  • 4. Load RDF/XML into triple store
    Using the Talis Platform triple store
    RDF/XML is HTTP POSTed
    We’re using Pynappl
    Python client for the Talis Platform
    http://code.google.com/p/pynappl/
    Store provides us with a SPARQL query interface
  • 5. Create Linked Data Views
    Expose ‘bounded’ descriptions from the triple store over the Web
    Make available as documents in both human-readable HTML and RDF formats (also JSON, Turtle, CSV)
    Using Paget ‘Linked Data Publishing Framework’
    http://code.google.com/p/paget/
    PHP scripts query Sparql endpoint
  • http://data.archiveshub.ac.uk/id/archivalresource/gb1086skinner
  • http://data.archiveshub.ac.uk/
  • Can I access the Locah Linked Data?
    Will be releasing the Hub data very soon!
    Copac data will follow approx 1 month later
    Release will include Linked Data views, Sparql endpoint details, example queries and supporting documentation
  • Reporting on opportunities and barriers
    Locah Blog (tags: ‘opportunities’ ‘barriers’)
    Feed into #JiscEXPO programme evidence gathering
    More at:
    http://blogs.ukoln.ac.uk/locah/2010/09/22/creating-linked-data-more-reflections-from-the-coal-face/
    http://blogs.ukoln.ac.uk/locah/2010/12/01/assessing-linked-data
  • Creating the Visualisation Prototype
    Based on researcher use cases
    Data queried from Sparql endpoint
    Use tools such as Simile, Many Eyes, Google Charts
    For first Hub visualisation using Timemap –
    Googlemaps and Simile
    http://code.google.com/p/timemap/
  • Visualisation Prototype
    Using Timemap –
    Googlemaps and Simile
    http://code.google.com/p/timemap/
    Early stages with this
    Will give location and ‘extent’ of archive.
    Will link through to Archives Hub
  • Sir Ernest Henry Shackleton
    http://archiveshub.ac.uk/data/gb15sirernesthenryshackleton
    Archives related to Shackleton:
    VIAF URL: http://viaf.org/viaf/12338195/
    Books related to Shackleton:
    Biographical History:
    Ernest Henry Shackleton was born on 15 February 1874 in Kilkea, Ireland, one of six children of Anglo-Irish parents. The family moved from their farm to Dublin, where his father, Henry studied medicine. On qualifying in 1884, Henry took up a practice in south London, and between 1887 and 1890, Ernest was educated at Dulwich College. On leaving school, he entered the merchant service, serving in the square-rigged ship Hoghton Tower until 1894 when he transferred to tramp steamers. In 1896, he qualified as first mate, and two years later, was certified as master, joining the Union Castle line in 1899. [more]
  • The challenges
  • The learning process
    Model the data, not the description
    The description is one of the entities
    Understand the importance of URIs
    Think about your world before others
    …but external links are important
    Try to get to grips with terminology
  • Names
    6947115KNAPPF
    F Knapp associated with record 6947115
    /id/agent/6947115KNAPPF
    <copac:isCreatorOf rdf:resource="http://data.copac.ac.uk/id/mods/6947115"/>
    6957115KNAPPF
    6947115
    <isCreatorOf>
  • Index terms (names, subjects, places)
    ‘AssociatedWith’ as the relationship
    Benefits of structured index terms
    Use /person/ and /organisation/ in the URI
    Distinguish /person/pilkington’ the person and /organisation/pilkington
    Distinguish place/reading/ and subject/reading/
  • Problems with source data
    EAD very permissive: whole range of finding aids
    Copac more consistent but still wide variety
    Hub EAD: We limited the tags we worked with
    Large files (around 5Mb) tend to need splitting up
  • Duplication of data
    “So statements which relate things in the two documents must be repeated in each. This clearly is against the first rule of data storage: don't store the same data in two different places: you will have problems keeping it consistent.” (T B-L www.w3.org/designissues/linkeddata.html)
  • Archival Inheritance
    “Do not repeat information at a lower level of description that has already been given at a higher level.” ISAD(G)
    Many elements do not apply to ‘child’ descriptions
    Simple rule of inheritance not always appropriate
    LD does assert hierarchical relationships but no requirement to follow these links
  • Copac
    Larger community: more potential vocabularies/documentation/support/confusion/inconsistencies
    Merged catalogues: a unique scenario
    ‘Creator’ and ‘Others’ (editor, authors, illustrator)
    Learning from Hub / Doing what is appropriate
    Usually not right or wrong answers
  • Copac model
    Groundwork done with Archives Hub. Then had to decide what we wanted to say about the data
    Challenges over what a ‘record’ is – ‘Bleak House’ from each contributor? or one merged record?
    In many ways simpler than archival data; but also can decide to create a simpler model
  • Copac Model
  • Copac specification
    Hard to start but proved to be very crucial
    Very iterative process between spec and RDF output
    Important to establish the structure of the spec (we used tabs for each ‘entity’)
  • Copac specification
  • Copac decisions
    Where to create Copac URIs –
    copac:creator
    copac:contributor
    copac:heldBy
    When to create URIs
    Title = literal
    Publication place = URI
    How to deal with problematic/ambiguous data
    Date? = productionDate
  • Issues
  • Risks
    Can you rely on data sources long-term?
    Persistence of persistent URIs?
    New technologies
    Investment of time – unsure of benefits
    Licensing issues
  • Provenance
    Track which data comes from our sources: URIs identify your entities
    Linked Data tends towards disassembling
    Copac/Hub as trusted sources…is DBPedia (for example) as reliable?
    Contributors may want data to be identified
    Issues around administrative/biographical history
    Benefits of trust?
    Users may want to know where data is from
  • Licensing
    Nature of Linked Data: each triple as a piece of data
    ‘Ownership’ of data?
    Data often already freely available (M2M interfaces)
  • Licensing
    Public Domain Licences: simple, explicit, and permit widest possible reuse. Waive all rights to the data
    BL, British National Bibiography uses public domain licence
    Limit commercial uses?
    Build in community norms: attribution, share alike - to reinforce desire for acknowledgement
    Legal situation?
  • Thank You
  • Attribution and CC licence
    Sections of this presentation adapted from materials created by other members of the LOCAH Project
    This presentation available under creative commonsNon Commercial-Share Alike:http://creativecommons.org/licenses/by-nc/2.0/uk/