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The DELOS Association for Digital Libraries has been established in order to keep the "DELOS spirit" alive by promoting research activities in the field of digital libraries.
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The 2nd International Workshop on Foundations of Digital Libraries will be held in Budapest (Hungary) on 20 Septemeber 2007, in conjunction with the 11th European Conference on Research and Advanced Technologies for Digital Libraries (ECDL 2007).
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A Reference Model for Digital Library Management Systems

Objectives | Perspectives | Highest level concepts | Members | Events | Documents


Despite the large number of software tools named “digital library systems”, there is no agreement yet on what Digital Libraries (DL) and Digital Library Management Systems (DLMSs) are and on which functionality they must provide. Existing systems are heterogeneous in scope and focus on very different aspects and functionality. These systems range from digital objects/metadata repositories, reference linking systems, archives and commercial systems that provide administration functions, to complex systems (mainly developed in research environments) that integrate advanced digital library services.

Research on DLMSs concerns several different areas. It is often difficult to compare or combine the results achieved in these areas since it is not always clear how they are related, and how they can impact on or constrain one another. This fragmentation of results hinders the embedding of new research achievements into real world systems.
These problems have a common origin: the lack of any agreement on the foundations for Digital Library Management Systems.

The objective of this DELOS activity is to define a DLMS reference model i.e. a formal and conceptual framework describing the characteristics of this particular type of information system. The model will exploit the understanding of the architecture and functionality expected from an operational DLMS which has been acquired by DELOS research groups over the years. This model will identify and characterize key concepts of a DLMS, such as the information space, documents handled, user profile, services, architecture, etc.

The reference model activity, begun in October 2004 by a core group of DELOS members, will soon be taken up by other DELOS groups, working from the perspectives of different domains. Liaisons with similar activities carried out by other research groups and initiatives at international level will be established in order to achieve a global and stable level of consensus on the model.


The problem of defining a DLMS can be approached from at least four perspectives, according to the different classes of actors involved:

  • DL end-users: the actors that exploit the DL funtionality for providing, consuming and managing the DL content. They perceive the DL as a stateful entity which serves their functional needs. The behavior of and the outcomes from the functions activated by these users depend on the state of the DL at the time of the request. The state of the digital library meant here comprises the managed collections of information objects and the set of authorized information users. This state changes during the digital library lifetime according to the functionality activated by the users and their inputs.

  • DL Designers: the actors that, by exploiting their knowledge of the application semantic domain, define, customize, and maintain the DL system aligned with respect to the information and functional needs of its end-users. In order to perform this task, they interact with the DLMS providing a number of functional and content configuration parameters. The former parameters specify aspects of the DL functionality perceived by the end-users like, for example, the result set format, the query language, the user profile formats, the document model, etc. The latter parameters define the third-party resources that are exploited by the specific DL, like repositories of content, ontologies, classification schemas, authority files, gazetteers, etc. The values of these parameters, which can be modified during the DL lifetime, determine the specific DL perceived by the end-users.

  • DL System Administrators: the actors that select the software components to install in order to implement the required DL system and decide where to deploy them. They interact with the DLMS by providing architectural configuration parameters, like the selected software components, the hosting nodes, the components allocation, etc. Their task is to identify the architectural configuration that better implements the DL system specified by the DL Designer by ensuring the required Quality of Service. The value of the architectural configuration parameters can be changed over the DL lifetime. The change of these parameters may result in the provision of a different DL functionality when a new software component is added and, more generally, can affect the quality of service.

  • DL Application Developers: the actors that develop the components that compose a DLMS. Dealing with software and application frameworks they realize both the functionality of the DLMS and of the DL system.

Each class of actors is looking for a DLMS reference model that satisfies its own particular requirements:

  • DL end-users: DL description – What functionality is provided by the DL? What information space can be accessed? What query language is used? Which metadata formats does the search service return? Does the DL ensure persistent availability?

  • DL designers: DLMS selection – What functionalities does the DLMS support? What type of information space can it manage? How does it allow the content to be ingested? What are the functionality configuration parameters?

  • DL System Administrator: DL maintenance - Which architecture and distribution are permitted? What are the deployment constraints on the services that implement the required functionalities? How does it scale down?

  • DL Application Developers: DLMS development and extension – What services a DL has to offer? What rules must be satisfied by any new service? Which communication protocol is used?

Highest level concepts

The DELOS Reference Model aims at providing a representation which characterizes existing and future DLMSs from at least the four perspectives listed above. It introduces the main concepts, the relationships between these concepts, and the constraints that hold among them. It also prescribes aspects that are mandatory for this type of information system. The figure below represents the highest level concepts of this model: Content is the entry point for all the concepts related to the content that is managed and disseminated by the DL e.g. collections, information space model, metadata, ontologies; User is the root for concepts like roles, communities, profiles, etc., that represent aspects of the DL users; Functionality is the entrance to that part of the model which concerns DL functions; Architecture regards software components, hosting nodes and how these are linked and constrained; Quality groups qualitative parameters characterizing the digital library behavior within a given operational domain; and, finally, Policy covers all the concepts that are related to established procedures or plans of actions governing the DL, such as collection management, preservation, access rights, etc.


Reference Model Executive Committee

  • Donatella Castelli, Istituto di Scienza e Tecnologie della Informazione (ISTI-CNR)

  • Yannis Ioannidis, University of Athens

  • Seamus Ross, HATII- University of Glasgow

Reference Model Technical Committee

  • Maristella Agosti, University of Padua

  • Leonardo Candela, ISTI-CNR

  • Milena Dobreva, HATII- University of Glasgow

  • Nicola Ferro, University of Padua

  • Akrivi Katifori, University of Athens

  • Georgia Koutrika, University of Athens

  • Carlo Meghini, ISTI-CNR

  • Pasquale Pagano, ISTI-CNR

  • Heiko Schuldt, University of Basel

  • Dagobert Soergel, University of Maryland



For further information please contact:
Donatella Castelli, Istituto di Scienza e Tecnologie della Informazione (ISTI-CNR)

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