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Linking resources

Linking resources. Praha, June 2001 Ole Husby, BIBSYS ole.husby@bibsys.no. Linking resources. = linking of resources ? = resources for linking ?

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Linking resources

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  1. Linking resources Praha, June 2001 Ole Husby, BIBSYS ole.husby@bibsys.no

  2. Linking resources = linking of resources ? = resources for linking ? "Identifying and categorizing relations is a necessary requirement for the formal description that makes navigation possible in the bibliographic universe" (Knut Hegna)

  3. What is a link? A link is an expression of a relation or A link is a connection from one page to another destination such as another page or a different location on the same page :=( or A link is underlined and blue :=(

  4. Different types of relations • Aggregate (whole / part) • Generic • Associative • Some relations are a priori given by the nature of things • While others are made up by us • Still others are deduced from statistics

  5. FRBR • FRBR (Functional Requirements for Bibliographic Records) is modelling: • Entities • Attributes • Relations

  6. FRBR relations • between Work, Expression, Manifestation and Item: • E2 <translation of> E1 • M1 <manifestation of> E1 • to Persons and Corporate Bodies: • P1 <author of> W1 • I1 <owned by> C1

  7. more FRBR relations • to Concept, Object, Event, Place • W1 <is about> C1 • between Persons and Corporate Bodies: • P1 <often cites> P2 • P3 <often cited together with> P4 • between Concepts: • C1 <subspecies of> C2

  8. A link is an expression of a relation Different ways of expressing: • Citing together • Explicitly stating in text ("See:") • Using controlled vocabularies • Data modelling (relational databases) • Sharing metadata (identifiers etc.) • Linking in hypertext ( looks like this )

  9. New opportunities (and needs) • New opportunities offered by hypertext and especially the WWW • It's up to the user to click! • The omnipresence of the WWW has raised users' expectations in regard to linking everything together: • OPACS and A&I databases and Ejournals and other fulltext archives and . . .

  10. Links as entities in a digital library • Separate link databases are flourishing: • SilverLinker • CrossRef • Other commercial solutions • Proprietary solutions • Most are "closed" or "static" in some respect

  11. Reference linking from metadata (reference) to the full-content • The reference (source) may be held in a database or be a citation (more or less formally described) within some document • The full-content (target) may be "anything, anywhere" with a network identifier

  12. Some reference links • From an A&I database record to the full text • From a citation included in a document to the full text • From an OPAC record to an ejournal TOC with further linking possibilities

  13. Static links • Most linking architectures are static: • The links are precomputed ("just in case", "a priori") • The target space is a controlled environment • The links are "foolproof"

  14. Dynamic links • Dynamic links are created "a posteriori" (just in time) • The target space need not be controlled • Dynamic links are probabilistic: they might not work • The link creation can include link verification • but that probably takes too long

  15. CrossRef • A linking service operated by PILA (Publisher International Linking Association): • Implemented as a static link database • Link targets are DOIs • Access to the metadata -> DOI resolution requires PILA membership

  16. Extended service links • Reference links usually targets one specific copy of the full-content entity • But the user might need / prefer: • Full content from another supplier • An OPAC holdings description • A copy ordering / ILL service • Another metadata description / abstract • A book review or access to a net bookshop • A "full web" search

  17. Appropriate links • Every conceivable link is not appropriate to the user, because of • Diverse personal preferences (formats, delivery options etc.) • Diverse institutional preferences • Access restrictions • Temporary unavailability • These and other parameters constitute the context of the user

  18. Closed linking • Closed links are not context sensitive: • They might not work (access restrictions) • They ignore the policy of the user's library • They ignore the user's "real" needs and preferences

  19. Open linking • Open linking = context sensitive linking • Open linking architectures support extended services • One early implementation is SFX ("Special Effects"), now a part of the MetaLib product from Ex Libris

  20. OpenURL and service components • OpenURL is a framework for implementing open linking • The OpenURL is taken as input for a service component • There may be several service components available • OpenURL is under consideration as a NISO standard

  21. OpenURL "The OpenURL is designed to enable the transfer of the metadata from the information service to a service component that can provide context-sensitive services for the transferred metadata" (OPENURL SYNTAX DESCRIPTION http://www.sfxit.com/OpenURL/)

  22. OpenURL example http://scomp.bibsys.no/copy?sid=BIBSYS:ERL&issn=1234-5678 &date=1998&volume=12&issue=2&spage=134 Base URL Identifies the service component ORIGIN-DESCRIPTION (optional) Identifies the information service which is the source of the metadata OBJECT-DESCRIPTION Consists of the metadata for the information item

  23. Conclusions • As the digital library is globally distributed, we all have to work together! • Use persistent identifiers • Use open linking architectures • Implement extended services • Support the OpenURL syntax • Open up the CrossRef database for non-members !?

  24. References FRBR: Functional Requirements for Bibliographic Records: http://www.ifla.org/VII/s13/frbr/frbr.htm Reference linking, OpenURL: Look for articles by Herbert van de Sompel in the Dlib Magazine: http://www.dlib.org/dlib/

  25. Appendix: Linking in BIBSYS • Between OPAC records, using • MARC "linking entry fields" 76x - 78x • Supplementary proprietary mechanisms • Uniform titles, authority data • (simulating FRBR structure in a database of manifestations)

  26. More linking in BIBSYS • Between OPAC records and authors • Between thesauruses / classification schemes and OPAC records • Between OPAC records and full text • Using MARC field 856 (Electronic location) • Implementing URN:NBN resolving for Norwegian domain • Using separate link file for ejournals (context-sensitive)

  27. More linking in BIBSYS • Within digitized text documents • Using proprietary mechanism for linking the separate pages of scanned documents • From locally hosted A&I databases to BIBSYS holdings and copy request service • ERL (SilverPlatter), ISI • From third-party bibliographic databases to BIBSYS holdings and copy request service • OCLC FirstSearch, Ovid . . .

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