linking resources praha, june 2001 ole husby, bibsys [email protected]
TRANSCRIPT
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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)
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What is a link?
A link is an expression of a relation
orA link is a connection from one page to
another destination such as another page or a different location on the same page
:=(
orA link is underlined and blue :=(
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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
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FRBR
• FRBR (Functional Requirements for Bibliographic Records) is modelling:
• Entities• Attributes• Relations
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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
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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
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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 )
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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 . . .
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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
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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
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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
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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"
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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
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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
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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
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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
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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
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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
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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
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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 DESCRIPTIONhttp://www.sfxit.com/OpenURL/)
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OpenURL example
http://scomp.bibsys.no/copy?sid=BIBSYS:ERL&issn=1234-5678
&date=1998&volume=12&issue=2&spage=134
Base URLIdentifies the service component
ORIGIN-DESCRIPTION (optional)Identifies the information service which is the source of the
metadata
OBJECT-DESCRIPTIONConsists of the metadata for the information item
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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 !?
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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/
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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)
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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)
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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 . . .