Implementation of Digital LibrariesMichael L. Nelson
Old Dominion [email protected]
http://www.cs.odu.edu/~mln/
Congreso Internacional de Información en SaludLima, Peru
May 28, 2004
Acknowledgements
• ODU: K. Maly, M. Zubair, J. Bollen• LANL: R. Luce, X. Liu• NASA: G. Roncaglia, J. Rocker, C. Mackey• Cornell: C. Lagoze, S. Warner• MAGiC (UK): Paul Needham• and, of course, Herbert Van de Sompel
(LANL)– the OpenURL slides are nicked from his
presentations
Outline
• A bit of history• Core technologies & Issues
– OAI-PMH• deep web
– OpenURL– Handles / DOIs– Object Models
• Example implementations• Download and go…
covered only briefly
OAI-PMH
Background• I met Herbert Van de Sompel in April 1999...
– we spoke of a demonstration project he had in mind and had received sponsorship from Paul Ginsparg and Rick Luce
– We wanted to demonstrate a multi-disciplinary DL that leveraged the large number of high quality, yet often isolated, tech report servers, e-print servers, etc.
• most digital libraries (DLs) had grown up along single disciplines or institutions
– little to no interoperability; isolated DL “gardens”
– Universal Preprint Service• Demonstrated at Santa Fe NM, October 21-22, 1999
– http://web.archive.org/web/*/http://ups.cs.odu.edu/• D-Lib Magazine, 6(2) 2000 (2 articles)
– http://www.dlib.org/dlib/february00/02contents.html– UPS was soon renamed the Open Archives Initiative (OAI)
http://www.openarchives.org/
Result… OAI
• The OAI was the result of the demonstration and discussion during the Santa Fe meeting– OAI = a bunch of people, a religion, a cult, etc.– OAI Protocol For Metadata Harvesting (OAI-PMH) = the protocol
created and maintained by the OAI• Initial focus was on federating collections of scholarly e-print
materials…• …however, interest grew and the scope and application of
OAI-PMH expanded to become a generic bulk metadata transport protocol
• Note:– OAI-PMH is only about metadata -- not full text!
• but what is metadata vs. full-text?– OAI is neutral with respect to the nature of the metadata or the
resources the metadata describes• read: commercial publishers have an interest in OAI-PMH too...
OAI-PMH MechanicsRequest is encoded in http
Response is encoded in XML
XML Schema for theresponses are defined in the OAI-PMH document
Overview of OAI-PMH Verbs
Verb Function
Identify description of archive
ListMetadataFormats metadata formats supported by archive
ListSets sets defined by archive
ListIdentifiers OAI unique ids contained in archive
ListRecords listing of N records
GetRecord listing of a single record
archivalmetadata
harvestingverbs
most verbs take arguments: dates, sets, ids, metadata formatsand resumption token (for flow control)
resource
all available metadata about David
item
Dublin Coremetadata
MARCmetadata
SPECTRUMmetadata records
item = identifier
record = identifier + metadata format + datestamp
set-membership is item-level property
OAI-PMH Data Model
Data Providers / Service Providers
data providers(repositories)
service providers(harvesters)
Aggregators
data providers(repositories)
service providers(harvesters)
aggregator
aggregators allow for:• scalability for OAI-PMH• load balancing • community building• discovery
Aggregators• Frequently interchangeable terms:
– aggregators: likely to be community / institutionally focused
– caches: stores a copy, less likely to be community-oriented
– proxies: less likely to store a copy, may gateway between OAI-PMH and other protocols
• Dienst / OAI Gateway; Harrison, Nelson, Zubair, JCDL 03
• To learn more about aggregators, caches & proxies:– http://www.openarchives.org/OAI/2.0/guidelines-aggregator.htm– http://www.cs.odu.edu/~mln/jcdl03/
Example Aggregators
• Arc - http://arc.cs.odu.edu/– first described “hierarchical harvesting” in
D-Lib Magazine, 7(4) 2001• http://www.dlib.org/dlib/april01/liu/04liu.html
• Celestial - http://celestial.eprints.org/– among other services, it provides a history
of harvests (successful vs. errors)• http://celestial.eprints.org/cgi-bin/status
OAI-PMH 2.0 Registration
Data Providers: http://www.openarchives.org/Register/BrowseSites.plService Providers: http://www.openarchives.org/service/listproviders.html
150+ repositories registered
??? unregistered repositories
unregistered because:• testing / development• not for public harvesting • public, but “low-profile”• never got around to it…• ???
DP:SP ~= 5:1
Registration is Nice……But Not Required
• OAI-PMH is (becoming) the “http” for digital libraries– there is no central registry of http servers
• remember the NCSA “What’s New” page? (ca. 1994)
• There will never be “registration support” in OAI-PMH– registries are a type of service provider, built on top of OAI-
PMH– registration will be an integral part of community building– friends…
<friends>…</friends>
http://techreports.larc.nasa.gov/ltrs/oai2.0/ http://naca.larc.nasa.gov/oai2.0/
http://ntrs.nasa.gov/oai2.0/
http://ston.jsc.nasa.gov/collections/TRS/oai/
http://horus.riacs.edu/perl/oai/
harvester
Identify
NASA <friends> example
NACA Technical Report Server
• publicly available– began in 1996– details in NASA TM-1999-
209127 • scanned reports from
1917-1958– NACA = predecessor to
NASA• contents mirrored with
the MaGIC project– a UK-based grey-
literature preservation project
– OAI-PMH used to mirror contentshttp://naca.larc.nasa.gov/
http://naca.larc.nasa.gov/oai2.0/
NACA Report 1345
as seen through its native DLhttp://naca.larc.nasa.gov/
NACA Report 1345
as seen through MAGiChttp://www.magic.ac.uk/
NACA Report 1345
as seen through its Scirus(Elsevier)http://www.scirus.com/
NACA Report 1345
as seen through my.OAI(FS Consulting)http://www.myoai.com/
NASA Technical Report Server
• replacement for the previous distributed searching version of NTRS– MySQL– Va Tech harvester– modified “bucket”– details in Nelson, Rocker,
Harrison, Library Hi-Tech, 21(2) (March 2003)
• a service provider & aggregator– same OAI baseURL as
used for interactive searching
http://ntrs.nasa.gov/
NASA Technical Report Server
• advanced, fielded search
• explicit query routing – 12 NASA repositories– 4 non-NASA
repositories• turned “off” by
default
• >600k abstracts; >300k full-text
Service Providers• It is clear that SPs are proliferating, despite
(because of?) the inherent bias toward DPs in the protocol– easy to be a DP -> many DPs -> SPs eventually emerge– hard to be a DP -> SPs starve– currently 5x DPs more than SPs
• SPs are beginning to offer increasingly sophisticated services– competitive market originally envisioned for SPs is
emerging
Community Building
Colegio America
Colegio Universitario Andino
Pontificia Universidad Catolica del Peru
Universidad Nacional Jorge Basadre Grohmann
Universidad Nacional Mayor de San Marcos
Universidad Nacional de Trujillo
Universidad Peruana de Ciencias Apicadads
Universidad de Lima Universidad del Pacifico
Universidad Nacional Federico Villarreal
www.ndltd.org
OAI-PMH & The Deep Web
Exposing Repository Contents
• DP9: Webcrawler access to OAI-PMH repositories
• http://dlib.cs.odu.edu/dp9/• JCDL 02
http://www.cs.odu.edu/~liu_x/dp9/dp9.pdf
• An Apache module for OAI-PMH– http://www.modoai.org/
• Extensible Repository Resource Locators (ERRoLs) for OAI Identifiers – http://www.oclc.org/research/projects/
oairesolver/default.htm
Race for This New Market…
• Yahoo! & University of Michigan– http://www.umich.edu/news/
index.html?Releases/2004/Mar04/r031004
• Google & CrossRef– http://www.nature.com/nature/focus/
accessdebate/17.html
OpenURL
slides from Herbert Van de Sompel, LANL
The Context: Library Automation Environment anno 1998
• distributed information environment• local & remote A&I databases• rapidly growing e-journal collection• need to interlink the available information
The Problem: • links are delivered by info providers• links are not sensitive to user’s context
• appropriate copy problem• links dependent on business agreements between information vendors• links don’t cover the complete collection
Origins & Motivation
The Context: Library Automation Environment anno 1998
• distributed information environment• local & remote A&I databases• rapidly growing e-journal collection• need to interlink the available information
The REAL Problem:
• libraries have no say in linking • libraries are losing core part of the “organizing information” task• expensive collection is not used optimally• users are not well served
Origins & Motivation
Origins & Motivation
The Solution:
In information services:
• DO NOT provide a link which is an actual service related to a referenced item (e.g. a link from a record in an A&I database to the corresponding full-text)
• BUT rather provide• a link that transports metadata about the referenced item
to • others that are better placed to provide service links
OpenURL
Linking server operated by library
link source
link destination
link to referenced work .
resource
resolution of metadata into link
reference
non-OpenURL linking
resource
link
link source.
user-specific
resolution of metadata & identifiers into services
reference
OpenURL linking
OpenURL
OpenURLlinking
server
provision of OpenURL
linklink
destination
linklink
destinationlink
linkdestination
linklink
destination
transportation of metadata & identifiers
context-sensitive
metadata planeresource1
resource2 resource3
default links
herbert van de sompel
default links:• restricted in nature• action-radius restricted by business agreements• not context-sensitive
metadata plane
extended services plane
resource1
servicecomponent1
servicecomponent2
default links
appropriate linksOpe
nURL
resource2 resource3
herbert van de sompel
NISO OpenURL Standardization Charge
• Use existing “OpenURL Framework” as starting point• notion of context-sensitive services• notion of transporting “contextual” metadata packages to obtain context-sensitive services
• Define syntax and transport-method for “contextual” metadata packages
• Ensure extensibility:• must support future applications• must support other information communities
=> Generalize and Standardize
NISO OpenURL Standardization Charge
Therefore, to be addressed were:
• OpenURL Framework beyond scholarly resources
• “contextual” metadata packages
• Syntax for “contextual” metadata packages
• Transport of “contextual” metadata packages
OpenURL Status
• (Nearly) a NISO standard– check for details:
• http://library.caltech.edu/openurl/
Naming: Handles & DOIs
Naming
• Fundamental to other technologies (OAI-PMH, OpenURL, etc.)
• Options– URNs– Persistent URLs (PURLs)
• http://purl.org/
– Handles• http://www.handle.net/
– Digital Object Identifiers• http://www.doi.org/
– ARK• http://www.cdlib.org/inside/diglib/ark/
“Inverted Archives”
• Unit of discourse is no longer an archive or service, but a DOI which has services linked from it– cf.:
• UPS demonstration prototype• “Smart Objects, Dumb Archives” (SODA)
model
Example
http://dx.doi.org/10.1145/374308.374342
Object Models
Popular Object Models
• METS– used in DSpace, Fedora– http://www.loc.gov/standards/mets/
• MPEG-21 DIDL– http://xml.coverpages.org/mpeg21-didl.html– used in LANL DLs
• http://www.dlib.org/dlib/november03/bekaert/11bekaert.html• http://www.dlib.org/dlib/february04/bekaert/02bekaert.html• http://lib-www.lanl.gov/~herbertv/papers/jcdl2004-submitted-
draft.pdf
Object Models & OAI-PMH
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
resource
item oai:foo.edu:1234
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
METS
Move from simple metadata files“pointing” to resources…
…to records as “modeled representations” of resources
records
Download and Go!
Where Do You Want to Build?
user
. . .dataprovider
dataprovider
dataprovider
dataprovider
serviceprovider
local context-sensitive services
EPrints.org
dataprovider
CDSware
CDSware
Fedora
• joint project between Cornell & UVa – funded by the Mellon Foundation
• a repository management system– focuses on complex digital objects and their
behaviors
• more info:– http://www.fedora.info/– D-Lib Magazine, 9(4)
• http://www.dlib.org/dlib/april03/staples/04staples.html
• MIT + HP Labs• constructed to capture all the output of
MIT’s faculty• now generalized to the DSpace Federation
– 8 top universities in the US & Canada
• More info:– http://www.dspace.org/– http://sourceforge.net/projects/dspace/– D-Lib Magazine 9(1)
• http://www.dlib.org/dlib/january03/smith/01smith.html
EPrints.org
• developed at Southampton University– part of larger suite of institutional/author
self-archiving tools and services• e.g.: citebase; paracite
• widely adopted -- 100+ sites– http://software.eprints.org/#ep2
• more info– http://www.eprints.org/– http://www.arl.org/sparc/core/index.asp?pag
e=g20#6
CDSware
• developed at CERN• data provider & service provider• large-scale use @ CERN (> 600k
records)– in use at a few non-CERN sites
• free & paid support models• more info
– http://cdsware.cern.ch/
• P2P publishing for academia– community servers for coordination,
management– archivelets for individual laptops, PCs
• more info:– http://kepler.cs.odu.edu/– D-Lib Magazine 7(4)
• http://www.dlib.org/dlib/april01/maly/04maly.html
• developed by UKOLN– open source
• OpenURL 0.1 format resolver– NISO 1.0 format???
• more info:– Ariadne, 28
• http://www.ariadne.ac.uk/issue28/resolver/• ftp://ftp.ukoln.ac.uk/metadata/tools/openresolver/• http://www.ukoln.ac.uk/distributed-systems/openu
rl/
Conclusions
Why The OAI-PMH is NOT Important
• Users don’t care• OAI-PMH is middleware
– if done right, the uninterested user should never have to know
OAI
Inside
• Using OAI-PMH does not insure a good SP
• OAI-PMH is (or is becoming) HTTP for DLs– few people get excited about http now
• http & OAI-PMH are core technologies whose presence is now assumed
Digital Library Technologies
• http• XML• OAI-PMH• OpenURL ?
Other Uses For the OAI-PMH• Assumptions:
– Traditional DLs / SPs will continue on their present path of increasing sophistication
• citation indexing, search results viz, personalization, recommendations, subject-based filtering, etc.
– growth rates remain the same (5x DPs as SPs)• Premise: OAI-PMH is applicable to any scenario that needs
to update / synchronize distributed state– Future opportunities are possible by creatively interpreting
the OAI-PMH data model• See Van de Sompel, Young & Hickey, D-Lib Magazine July 2003,
http://www.dlib.org/dlib/july03/young/07young.html• Nelson, 2nd OAI Workshop,
http://agenda.cern.ch/askArchive.php?base=agenda&categ=a02333&id=a02333s5t8/transparencies
OpenURL Framework evolution
A spec based on HTTP GET to transport metadata about• a scholarly referent & • the context in which the referent is referenced
Draft Van de Sompel, Beit-Arie, Hochstenbach - 05/2001
A framework Standard that enables different Communities to:• describe a referent• describe the context in which the referent is referenced• transport these descriptions
NISO Draft Standard -04/2003
The Future: Community Building
• Ultimately, protocols and metadata formats are not what makes a difference
• Rather, the critical mass afforded by a common set of utilities (cf. http, Dublin Core, XML)
• The best current example: The Open Language Archives Community – http://www.language-archives.org/
• OAI-PMH provides the basis for communication between strangers, but allows even richer communication between friends
Further Reading• Gerry McKiernan, Library Hi-Tech News
– http://www.public.iastate.edu/~gerrymck/OAI-SP-I.pdf– http://www.public.iastate.edu/~gerrymck/OAI-SP-II.pdf– http://www.public.iastate.edu/~gerrymck/OAI-SP-III.pdf
• Open Archives Forum OAI-PMH Tutorial– http://www.oaforum.org/tutorial/
• “A Survey of Digital Library Aggregation Services”– http://www.diglib.org/pubs/brogan/
• Open Access News– http://www.earlham.edu/~peters/fos/fosblog.html
• Guide To Institutional Repository Software– http://www.soros.org/openaccess/software/
Great Stuff I Did Not Cover…
• OAI-PMH– Static Repositories
• http://www.openarchives.org/OAI/2.0/guidelines-static-repository.htm
– OAI-Rights• http://www.openarchives.org/documents/
OAIRightsWhitePaper.html• http://www.openarchives.org/news/
oairightspress030929.html
• Digital Preservation– http://www.digitalpreservation.gov/