TOWARDS THE DEVELOPMENT OF A GENERAL-PURPOSE
DIGITAL REPOSITORY
Dimitrios A. Koutsomitropoulos, Anastasia A. Tsakou, Dimitrios K. Tsolis and
Theodore S. Papatheodorou
High Performance Information Systems Laboratory, Department of Computer Engineering and Informatics, University of
Patras, Rio 26500, Patras, Greece
Keywords: Repositories, Functional Model, Preservation, Interoperability, OAIS.
Abstract: The need for efficient storage, management and consumption of digital resources has long been a puzzle for
institutions and organizations that aim at preserving digital information. Numerous standards, specifications
and practices have been proposed so far, in order to alleviate the problems that come in to surface when
setting up a digital repository. Nevertheless, only few of these initiatives have enjoyed wide spread
adoption, possibly because they are bound to specific content, functionality or implementation needs. This
paper aims to contribute towards the development of a general-purpose digital repository by first providing
a common definition, independent of specific needs and thus widely applicable. It also presents a set of
state-of-the-art requirements that are of key importance for the success of any similar task. Finally, it
proposes a Functional Model so as to demonstrate how the above specifications can actually be realized.
1 INTRODUCTION
The maintenance and preservation of digital
resources is an important challenge and a significant
matter that has so far concerned several
organizations and institutes. Although several
standards, criteria and mechanisms have been used
for an efficient and flexible way of creating and
managing digital objects, there is still the need for a
complete and efficient model that will facilitate the
establishment of digital repositories.
One important step towards this direction has
been accomplished by the joint RLG-Commission
on Preservation and Access Task Force on
Archiving Digital Information in 1994. The
CPA/RLG report (RLG-OCLG 2001) proposes the
definition of a trusted digital repository, identifies
the primary attributes of this repository, articulates a
framework for the development of a certification
program and makes several recommendations for
future work. Work in these areas has been advanced
by the Consultative Committee for Space Data
Systems in its Reference Model for an Open
Archival Information System (OAIS) (CCSDS
2002) and by many groups and individual
institutions that are designing their own digital
repository systems. Fedora (Payette and Staples
2002; Payette and Lagoze 1998), Dspace (Bass et al.
2002; MacKenzie 2002), Dienst (CDRLG 2000) and
GreenStone (NZDL 2003) are some examples of
such systems and architectures of digital
repositories. However, this broad interest in digital
repositories has revealed that there are still certain
issues under concern. More specifically, a clear,
independent and widely acceptable definition for a
digital repository does not exist. In addition, critical
requirements from a variety of perspectives need to
be identified, in order to provide a basis for future
initiatives and assist to the construction of a “best-
practices” framework. Finally, the proposal of a
robust and sound functional model can demonstrate
the possibility of integrating various technologies,
standards and architectural principles in order to
reap the benefits of a universal, general-purpose
digital repository.
The rest of this paper is organized as follows;
Section 2 attempts to provide definitions for a
general-purpose digital repository; Section 3
describes a series of key requirements that any
repository implementation has to satisfy; Section 4
describes a functional model so as to illustrate how
these requirements can actually take effect. Finally,
Section 5 summarizes our conclusions and future
work.
271
A. Koutsomitropoulos D., A. Tsakou A., K. Tsolis D. and S. Papatheodorou T. (2004).
TOWARDS THE DEVELOPMENT OF A GENERAL-PURPOSE DIGITAL REPOSITORY.
In Proceedings of the Sixth International Conference on Enterprise Information Systems, pages 271-278
Copyright
c
 SciTePress

2 DEFINING THE DIGITAL
REPOSITORY
The strict definition of the term "digital repository"
is an issue that generates a lot of discussion and it is
almost certain that unanimity for a common
definition would not be achieved. One of the main
reasons for this ambiguity is that a digital repository
is mainly characterized by the type of content that
makes available and by the reasons that necessitate
its creation and functionality. However, technical
knowledge is not required in order to understand that
the following intuitional definition is correct:
Definition 1: A Digital Repository is a collection of
digital entities that are subject to the following three
operations: insertion, deletion and retrieval.
This abstractive and simple definition obviously
provides a minimal set of requirements for any
digital repository. One more refined definition is the
following:
Definition 2 (RLG): A Digital Repository is an
organization that has the responsibility for long-term
preservation
1
of digital resources, as well as for
making them available to communities agreed on by
the producer and the management authority of the
repository.
The need for long-term preservation has long
been recognized by important institutions that
implement digital repositories (libraries, digitization
organizations, standardization consortia etc), as well
as by the European Union regarding digitization of
cultural heritage (e.g. Spanish Presidency resolution
(European Council 2002)). Further analysis of the
importance of long-term preservation is outside the
scope of this paper.
Let us consider the digital repository as a closed
system. Then the digital repository interacts with
three entities of the external environment as shown
in Figure 1.
Producer: Is the role that corresponds to those
people or client systems which provide the
information to the repository.
Management: Is the role that corresponds to those
people who set the overall policy of the repository,
1
The action of preserving information in a correct and
"independently understandable", long-term form. For
more information please refer to (CCSDS 2002).
as one component in a broader policy domain. In
other words, the management control of the
repository reflects only one of Management's
responsibilities.
F
igure 1: The interaction model between the Digital
Repository and the Environment
Consumer: Is the role that corresponds to the people
or client systems that interact with the repository's
services in order to find and retrieve archival
information of their interest. One special class of
consumers is the Designated Community.
We have now set the stage for the following
final definition that derives from OAIS:
Definition 3 (OAIS): A Digital Repository is an
archive that aims at the preservation of digital
information for access and use by a Designated
Community and satisfies specific requirements
2
.
Notice that none of the above definitions is
biased towards a specific design or implementation.
3 REQUIREMENTS FOR A
DIGITAL REPOSITORY
Having in mind the above digital repository
definitions and taking into account current research
in the field of digital repositories and digital libraries
we recognize a series of six requirements that every
digital repository has to satisfy. In the following,
each of these requirements is explained and justified
in brief.
2
These requirements are described in detail in (CCSDS
2002). They pertain mainly to the quality of the
repository services and to IPR issues.
ICEIS 2004 - HUMAN-COMPUTER INTERACTION
272

Long Term Preservation / Access to the
repository’s content: A significant step towards
preserving digital assets and ensuring their
accessibility in the long term is to develop a digital
repository conformant to the OAIS specification.
Content should also be characterized by the ability
of permanent access (e.g. by persistent URI’s). At
the same time the repository should maintain
multiple versions of the content, because digital
objects may be modified / updated from time to time
(persistency).
Metadata: Metadata should be used during the
whole life-circle of the digital content. The main
objectives are description of digital content, support
for its management and facilitation of access to it,
even in the long term (descriptive, administrative,
preservation metadata). However, it is important for
the metadata to follow a widely adopted standard
(Dublin Core (DCMI 2003) can be used in general,
MPEG-7 (MPEG 2003) for multimedia content,
DIG-35 (DIG 2000) for digital images and METS
(DLF 2003) for wrapping and encoding all the
above). Furthermore, there are cases where metadata
should not only be used for describing individual
repository objects but should also support a higher
level of abstraction, i.e. the collection level (Dublin
Core-Collection Level Description).
Interoperability / Import-Export Capability:
Interoperability can be achieved by adopting well-
known standards during the repository’s
development. One of them is the platform-
independent language XML (and XML Schema).
Implementation of the OAI-PMH protocol (Lagoze
and Van de Sompel 2001), (Van de Sompel and
Lagoze 2002) is highly recommended in order to
accommodate mass metadata import/export to and
from the repository. Support for the Z39.50
(ANSI/NISO 1995) protocol is also of crucial
importance, especially for transparent and remote
search in a huge amount of documents.
Interoperability and accessibility of the digital
repository are enhanced by exposing its services as
Web Services. Practically, this means that the
services will be described using the WSDL language
(W3C 2003) and registered with some UDDI
registry (OASIS 2002). The major benefit of UDDI
is that it enables the automate discovery (and
possibly utilization) of a Web Service by the
machine, similar to the way that physical users use
search engines. Recently, attention seems to draw
the ZING Initiative (“Z39.50 International: Next
Generation”) (Z39.50 IMA 2003) and especially its
SRW (“Search/Retrieve for the Web”) part. SRW is
a web-service-based protocol which aims to
integrate access across networked resources, and to
promote interoperability between distributed
databases by providing a common platform. It
features XML and SOAP and thus it is able to
integrate more tightly with XML-based
infrastructures.
Security/ User Certification: It is clear that none
but the Designated Community will be allowed to
access the repository’s content. A practical way to
achieve this is to establish a set of access policies for
each Consumer or Consumers' Community, to
support their authentication using login/password
pairs and/or digital certificates and to cipher access
to the repository’s services (e.g. SSL).
Intellectual Property Rights Management: The
need for copyrighting original content and for
economic exploitation of the repository necessitates
the management and encoding of IPR information
into the content. Watermarking not only for digital
images but also for any type of multimedia content
is widely used. At a metadata level, we indicatively
mention the XML-based MPEG-21, Part 5: Rights
Expression Language (MPEG 2002) and the W3C’s
XML security suite (XML Encryption, XML Key
Management and XML Signature).
Knowledge Representation / Management:
Repository's content will not be restricted within
only one thematic domain, but it may also span over
several domains or their combinations.
Consequently, it is convenient to describe the
content in a semantically hierarchical and structural
way. In other words, the establishment of ontologies
for each content domain is proposed. For example,
the CIDOC ontology (CRM-Conceptual Reference
Model (Crofts et al. 2001) can be used for the
cultural heritage domain. An ontology-enabled
system can assist the user in his search by supporting
automated reasoning, even if the information being
sought is not explicitly defined in the metadata.
Ontologies can also be used for the management of a
digital repository; e.g. ABC (Lagoze and Hunter
2001) is capable of organizing events that occurred
in the repository at any moment. Traditionally, RDF
is used for the development of ontologies; however
the DAML+OIL (McGuinness et al. 2002) and the
more recent OWL language (W3C 2003) are
recommended, as they are specifically designed for
ontologies.
4 DIGITAL REPOSITORY
FUNCTIONAL MODEL
Implementing the above requirements results to the
following Functional Model of the digital repository
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273

(Figure 2). This functional model is in fact a
refinement of the digital repository definition as a
closed system, and describes the details of its
internal organization as well as its interaction with
the external entities Producer, Consumer and
Management. It is worthy noting that the functional
model proposed here does not necessarily conform
to the OAIS reference model. Instead, the
conformance to the OAIS specification is left as a
designer’s choice together with other design choices
(see Section 4.3).
The functional model is divided in to four major
layers: Insertion, Repository
3
(Actual Storage),
Management and Consumption.
Figure 2: Digital Repository General Functional Model
4.1 Insertion
The Producer has to provide the entity to be
preserved in digital format. It is also the Producer’s
responsibility to provide this entity in acceptable by
the repository, accessible and error-free formats (see
OAIS - Submission Agreement). Since a digital
object is made available, it is inserted in the
repository in two parallel components (Figure 3):
• Binary Upload: The digital (binary)
representation of the object is stored in the
3
In order to solve ambiguity between the “digital
repository” as a whole and the Repository layer, we refer
to the latter with a capital “R”.
repository. This is really an interface through
which the Producer can upload files to the
repository. The binary file, after being properly
watermarked, is stored in the repository’s
database.
• Metadata attachment: Depending on content
type, the metadata schemata to be followed are
decided in advance. Based on these schemata,
the Producer will be provided with a series of
forms consisting of the necessary metadata
fields that have to be completed (Manual
Insertion), while efforts will be made to
enhance automated metadata extraction
(Automated Extraction), whenever possible (e.g.
the dominant colors of a picture). This is also
the phase where the metadata pertaining to the
intellectual property rights of the content are
being inserted. Before the metadata are stored in
the repository, they are properly encoded and,
possibly, ciphered.
Figure 3: Digital Repository Functional Model in detail:
The Insertion Layer
4.2 Repository (Actual Storage)
This is the layer where the content is actually being
stored. Figure 4 shows the internal organization of
the Repository layer as well as its interaction with
the other layers. The Repository layer takes as input
the products of the Insertion layer, feeds the
Consumption layer and is externally affected by the
Management layer choices.
Since the insertion of a digital entity is being
conducted in two separate components (file +
metadata), actual storage follows a similar manner.
We have therefore to deal with the problem of
storing two conceptually separated components: the
binary file, where the digital entity is binary
encoded, and its accompanying metadata.
Depending on the extent to which these components
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are also physically separated, we come up with the
following design choices:
• Relationally biased solution: Store files as well
as metadata in a multimedia data base. The files
are stored as BLOBS and an Entity-Relationship
(ER) schema is being designed, which will
guide the construction of the corresponding
tables in the DB. Metadata are stored in the
fields of the aforementioned tables. The
problem of disseminating XML information that
naturally arises, since XML documents are
banned from this solution, can be met by
dynamic, on-demand XML document
generation from the DB fields. The advantage of
this solution is that metadata are directly related
to the content they describe, through the ER
model relations.
• Document-biased solution: In this solution,
metadata are also physically separated from the
content. Digital files are stored in the
multimedia DB, possibly along with some other
information (like labels, pointers, identifiers
etc), while metadata are stored separately in an
XML Document Repository. The latter may be
either proprietarily developed or it can be based
on some commercial native XML DBMS. The
burden of linking together the objects that are
stored in the DB with their metadata is placed
over business logic, as there is no other away to
associate the two components. In other words,
there is a need for much more code to be
developed as well as for unique identifiers to be
used, not only in the DB, but also in the XML
documents, in order to maintain consistency;
that is, the XML documents point to those
objects that they actually describe. Efficient
information retrieval from an XML document
collection is achieved using the SQL-like XML
query languages: XQuery and XQL.
• Unbiased solution: Finally, a more balanced
solution is to use a relational DB with native
XML support (so far Oracle 9i Release 2 and, to
a lesser extent, IBM DB2 with XML
Extenders). Thus, linkage between content and
metadata is more imminent than in the previous
solution, for both are virtually managed by the
same DMBS. At the same time, metadata
remain satisfyingly separated from the content,
as they are independently stored in XML
documents and follow their own schema.
In any case, digital objects are related to XML
documents with a 1:n relationship. An XML
document can therefore correspond to multiple
digital objects, thus fulfilling the requirement to
describe the content also in the collection level.
Separating content from its description, even
physically, seems to be the dominant practice in
related academic initiatives for repository
development (e.g. in (Payette and Staples 2002;
McKenzie 2002)). The main advantages of such an
approach are summarized below:
• Content information autonomy: Since the
accompanying information of a digital
object,(that is, its metadata) are separated from
the object itself, they are completely
autonomous. In this way, even in the case of DB
failure or break-down, the digital repository
remains capable of disseminating object
information, despite the fact that the object itself
is not accessible.
Figure 4: Digital Repository Functional Model in detail:
The Repository (Actual Storage) and the Management
Layers
• Support for XML-oriented Standards and
Interoperability: Many consumption standards
that enjoy great popularity nowadays (like, for
example, ΟΑΙ), demand to be provided with
information in XML format. In addition,
separate storage of the XML documents seems
to be a more natural and, most important, a
more efficient solution, especially in the case of
mass consumption, compared to dynamic XML
document generation from a DB. In addition,
the XML’s platform–independent nature, its
human / machine readable characteristic and its
wide-spread adoption in the previous years
render it ideal for achieving interoperability
with almost every up-to-date information
system.
• Straightforward modification of the metadata
schema: XML Schema language is designed
and proved to be a powerful tool for designing
schemata for XML documents and establishing
the necessary constraints. By using XML
TOWARDS THE DEVELOPMENT OF A GENERAL-PURPOSE DIGITAL REPOSITORY
275

Schema, the process of modifying or merging
metadata schemata is significantly simplified, in
contrast to modifying a relational DB schema. It
consists also the only efficient solution in the
case of an evolving, open (semi-structured)
schema, as it is frequently the case with
metadata schemata.
On the other hand, a complete physical
separation between content and metadata has the
side-effect of manually maintaining consistency
between content and its description and incurs the
corresponding programming burden. Finally, it is
still open whether a relational DB is more efficient,
as a whole, than a native XML DB (e.g. are queries
actually answered faster? (Bourret 2003; Florescu
and Kossmann 1999)).
4.3 Management
Management here has a meaning similar to the one
given in the OAIS definition, that is, management is
external to the repository and has nothing to do with
the day-to-day maintenance / administration of its
content. According to the OAIS specification,
management typically is responsible for negotiating
financial resources, conducting some regular review
process for progress evaluation, determining pricing
policies for OAIS services and resolving conflicts
involving the external entities that interact with the
repository. Effective management should also
“provide support for the OAIS by establishing
procedures that assure OAIS utilization within the
repository” (CCSDS 2002). In the functional model
proposed here, Management is also considered to
include, in addition to the above, the series of the
optional design choices which, if implemented, can
affect the repository from the inside. In particular,
these choices include (see Figure 4):
• Conformance to the OAIS reference model: It
involves the establishment of entities and
procedures in order for the digital repository to
conform with the OAIS specifications as a
whole.
• Ontology-based content indexing: Digital
objects that are ingested by the repository
should be indexed based on the ontology
describing the domain they belong to. More
specifically, every repository object will be
related to its ontology class and, subsequently,
to its corresponding properties. Typically, these
ontologies will be expressed in OWL or
DAML+OIL format. Maintenance and
evolution of these ontologies will be driven by
the metadata produced during Insertion, with
little manual intervention or even in a fully
automatic manner (Alani et al. 2003). Ontology-
based indexing will later allow for content
understandability by intelligent agents and for
“intelligent queries” submission.
• Persistency: This is about ensuring persistent
access to the content and keeping multiple
versions of the digital objects. It may be
considered internal responsibility of the DBMS
(at least for storing and keeping track of
multiple versions).
• Internal DBMS Administration Procedures:
These are the common internal procedures of a
database, including for example indexing,
organization of the information on the physical
medium (disk), ER relationship model etc. It
may be considered as a design choice, in the
sense of the appropriate DB system selection.
Part of the day-to-day repository administration
is conducted by these functions.
4.4 Consumption and Access Policies
The Consumption layer provides the appropriate
interfaces that allow the Consumer Communities to
consume the content and access the services of the
repository. Between the Repository and the
Consumption layer lays the intermediate sub-layer
of Access Policies.
Figure 5: Digital Repository Functional Model in detail:
The Consumption Layer and the Access Policies sub-
Layer
In this functional model, Access Policies include
the implementation of the Security / User
Authentication requirements for the digital
repository. This sub-layer therefore contains the part
of business logic that ensures effective control of
access to the repository content and services by
Consumers. Access policies must provide for
smooth and unobstructed access to the repository by
the Designated Community, according to the Order
Agreement (see (CCSDS 2002) & Definition 2). In
other words, Access Policies make available whole
or part of the content to all or specific users or user
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communities, check whether the user who requests
consumption actually fulfills the necessary
requirements in order to be served (e.g. billing) and
determine whether whole or part of the content will
be available through all or specific Consumption
interfaces.
The following interfaces are proposed for the
Consumption layer:
• User Queries: The designated user of the
repository should be able to submit queries to
the repository databases, as a means to retrieve
information and content from it. In fact, the user
queries interface is implemented by providing
the ability to submit SQL / XQL queries in a
user-friendly manner. As a result, the user will
be presented with the digital objects as well as
(all or part of) their accompanying metadata. In
addition, the user should be able to exploit the
repository ontologies and submit intelligent
queries: He should be able to retrieve
information, even if this information is not
explicitly stored in the repository. Except of the
query submission capability, the user should
also be able to navigate through the repository,
using a hierarchical (ontological or other)
organization of the content.
• Intelligent Agents: The ontologies constructed
for the content and services of the repository
will allow for its access and consumption by
intelligent agents. Agents should be able to
submit intelligent queries to the repository and
negotiate content and information provision in
an automatic and transparent way. Agents will
also contribute in augmenting or modifying the
repository ontologies.
• OAI: The digital repository can function as Data
Provider making available its metadata
according to the OAI-PMH protocol. Apart
from the Consumption layer, the repository may
support OAI as Service Provider as well: It will
receive metadata by other Data Providers
(Insertion layer) and make them available for
consumption.
• Z39.50: The repository can function as a server
providing its information, by supporting the
Z39.50 client / server communication protocol
for information retrieval. Support for Z39.50
will allow remote client systems to access the
repository; these systems in turn will make the
retrieved information available to their end
users. Since Z39.50 is an internationally
standardized protocol for information retrieval
(ANSI / NISO), its support is of critical
importance for the repository interoperability.
As in the case of OAI, the repository can
support Z39.50 as a client, at the Insertion layer.
• UDDI: The digital repository may conform to
the UDDI specification, in order to be
discoverable, accessible and finally consumable
as a Web Service. Although the use of the
WSDL language for describing the repository as
a Web Service is not mandated by the UDDI
specification (version 3), it is recommended as a
best practice. Depending on its development
policy, the repository can also function as a
UDDI Node, and collect Web Services
information from other repositories. As a UDDI
Node, the repository can be part of a larger
UDDI Business Registry (UBR) or even
function as the Root Node of a domain-specific
registry.
5 CONCLUSIONS AND FUTURE
WORK
In this paper we tried to capture the meaning and
importance of a digital repository, and provided a
series of definitions that are independent of specific
content, functionality or implementation needs. We
also reviewed a series of key requirements for a
general purpose digital repository and argued that
they are of crucial importance for any relevant
initiative. Based on these requirements, we
developed a flexible, scalable and extensible
functional model, trying at the same time to maintain
a (thin really) equilibrium between abstract
functional design and detailed technical dictation of
implementation. Our previous discussion has also
shown that, in order to achieve elementary
functionality, it is not necessary to implement all the
interfaces proposed by the model; We are currently
following a process of incremental implementation
of the various repository’s components, deployed on
top of an existing open-source repository
framework. Future work will be focused on
migrating existing systems to the proposed
functional model and fine-tuning its components in
order to achieve seamless integration of
heterogeneous standards and maximum efficiency.
REFERENCES
Harith Alani, Sanghee Kim, David E. Millard, Mark J.
Weal, Wendy Hall, Paul H. Lewis and Nigel R.
Shadbolt, 2003. Automated Ontology-Based
TOWARDS THE DEVELOPMENT OF A GENERAL-PURPOSE DIGITAL REPOSITORY
277

Knowledge Extraction from Web Documents. IEEE
Intelligent Systems 18 (1).
ANSI/NISO, 1995. Z39.50-1995: Information Retrieval
(Z39.50) Application Service Definition and Protocol
Specification. http://lcweb.loc.gov/z3950/agency/
markup/markup.html
Michael J. Bass et al, 2002. DSPACE Internal Reference
Specification. Technology and Architecture
http://www.dspace.org/technology/architecture.pdf
Ronald Bourret, 2003. XML and Databases.
http://www.rpbourret.com/xml/XMLDatabases.htm
Consultative Committee for Space Data Systems, 2002.
CCSDS.650.0-B-1Q Reference Model for an Open
Archival Information System (OAIS). Blue Book.
Issue 1. http://wwwclassic.ccsds.org/documents/pdf
/CCSDS-650.0-B-1.pdf
Cornell Digital Library Research Group (CDLRG), 2000.
Dienst: Overview and Introduction.
http://www.cs.cornell.edu/cdlrg/dienst/DienstOvervie
w.htm
Nick Crofts, Ifigenia Dionissiadou, Martin Doerr,
Matthew Stiff, 2001. Definition of the CIDOC object-
oriented Conceptual Reference Model (version 3.2.1).
http://cidoc.ics.forth.gr/docs/
cidoc_crm_version_3.2.1.rtf
Digital Imaging Group. Inc, 2000. DIG-35 Metadata
Specification for Digital Images, Ver1.
http://www.i3a.org/i_dig35.html
Digital Library Federation, 2003. METS-Metadata
Encoding and Transmission Standard.
http://www.loc.gov/standards/mets/
Dublin Core Metadata Initiative, 2003. The Dublin Core
Metadata Element Set Version 1.1: Reference
Description.
http:///www.dublincore.org/documents/2003/02/04/dc
es/
European Council, 2002. Resolution on preserving
tomorrow’s memory – preserving digital content for
future generations. Official Journal no 2002/C 162/02.
http://europa.eu.int/eur-lex/
D. Florescu and D. Kossmann, 1999. Storing and querying
XML data using an RDMBS. IEEE Data Eng. Bull.
22(3): 27-34.
Carl Lagoze, Herbert Van de Sompel, 2001. The Open
Archive Initiative. Building a low-barrier
interoperability framework. Proceedings of the first
ACM/IEEE-CS joint conference on Digital Libraries:
54-62.
Carl Lagoze, Jane Hunter, 2001. The ABC ontology and
model. Journal of Digital Information, Special Issue -
selected papers from Dublin Core 2001 Conference.
Smith MacKenzie, 2002. DSpace: An Institutional
Repository from the MIT Libraries and Hewlett
Packard Laboratories. In: M.Agosti, C. Thanos (Eds.):
Research and Advanced Technology for Digital
Libraries. Lecture Notes in Computer Science 2458:
543-549.
Deborah L.McGuinness, Richard Fikes, James Hendler
and Lynn Andrea Stein, 2002. DAML+OIL: An
ontology language for the Semantic Web. IEEE
Intelligent Systems 17(5).
Moving Picture Experts Group, 2003. MPEG-7 Ver. 8.
http://mpeg.telecomitalialab.com/standards/mpeg-7/
mpeg-7.htm
Moving Picture Experts Group, 2002. MPEG-21
Overview ver 5. http://mpeg.telecomitalialab.com
/standards/mpeg-21/mpeg-21.htm
New Zealand Digital Library, 2004. GreenStone Digital
Library Software. http://www.greenstone.org
/english/home.html
OASIS UDDI Specifications TC, 2002. UDDI Version 3.0
Published Specification. http://uddi.org/pubs/
uddi_v3.htm20
Sandra Payette and Thornton Staples, 2002. The Mellon
Fedora Project. In: M.Agosti, C. Thanos (Eds.):
Research and Advanced Technology for Digital
Libraries. Lecture Notes in Computer Science 2458:
406-421.
Sandra Payette and Carl Lagoze, 1998. Flexible and
Extensible Digital Object and Repository architecture.
Second European Conference on Research and
Advanced Technology for Digital Libraries. Lecture
Notes in Computer Science 1513: 41-59.
RLG-OCLC, 2001. Meeting the Needs of Research
Resources: Attributes of a Trusted Digital Repository.
http://www.rlg.org/longterm/attributes01.pdf
Herbert Van de Sompel, Carl Lagoze, 2002. Notes from
the Interoperability Front: A progress Report on the
Open Archives Initiative. In: M.Agosti, C. Thanos
(Eds.): Research and Advanced Technology for
Digital Libraries. Lecture Notes in Computer Science
2458: 144-157.
World Wide Web Consortium, 2003. Web Services
Definition Language (WSDL) Version 1.2. W3C
Working Draft. http://www.w3.org/ TR/wsdl12/
World Wide Web Consortium, 2003. Web Ontology
Language (OWL) Guide Version 1.0. W3C Working
Draft. http://www.w3.org/TR/owl-guide/
Z39.50 International Maintenance Agency, 2003. Z39.50
International: Next Generation (ZING).
http://www.loc.gov/z3950/agency/zing/zing-
home.html
ICEIS 2004 - HUMAN-COMPUTER INTERACTION
278