7 Core Concepts

7 Core Concepts

Despite the diversity that exists in the digital library universe, a small number of fundamental concepts underlie every system. These concepts serve as a starting point for researchers to understand the field, for system developers creating and engineering a digital library, and for content providers seeking to render content through digital library technologies. Of the seven core concepts, Organisation is a special case in that it subsumes all the others.

Organisation
The Organisation concept concerns the entire Digital Library universe. A Digital Library is a kind of organisation in itself - a social arrangement pursuing a clearly defined goal, that is, a digital library service. This concept subsumes the mission for which the Digital Library has been conceived, the facets defining this mission and operating the resulting service. This concept should not be confused with the organisation or institution which decides to set-up the digital library and drive its development though there are overlaps and dependencies between the two. The institution establishes the Digital Library Organisation and is chartered with defining the overall service which the organisation is requested to provide. However, as an organisation in its own right, the Digital Library has the power to control its own behaviour and evolution in the framework defined by the institution. This concept is fundamental to characterise the Digital Library universe in that it highlights the commonalities between this universe and others that bring together an organised body of people for a particular purpose.

Content
The Content concept encompasses the data and information that the Digital Library handles and makes available to its users. It is composed of a set of information objects organised in collections. Content is an umbrella concept used to aggregate all forms of information objects that a Digital Library collects, manages and delivers. It encompasses a diverse range of information objects, including primary objects, annotations and metadata. This concept is fundamental to characterise the Digital Library universe because it captures one of the major resource these Organisations are called to manage, that is, the data and information that is made available.

User
The User concept embraces the various actors, whether human or machine, entitled to interact with Digital Libraries. Digital Libraries connect actors with information, supporting their ability to consume and creative use of it to generate new information. User is an umbrella concept including all notions related to the representation and management of actor entities within a Digital Library. It encompasses such elements as the rights that actors have within the system and the profiles of the actors with characteristics that personalise the system’s behaviour or represent these actors in collaborations. This concept is fundamental to characterise the Digital Library universe because it captures the actors of the overall Organisation.

Functionality
The Functionality concept encapsulates the services that a Digital Library offers to its different users, whether individual users or user groups. While the general expectation is that Digital Libraries will be rich in functionality, the bare minimum of functions includes new information object registration, search and browse. Beyond that, the system seeks to manage the functions of the Digital Library to ensure that the overall service reflects the particular needs of the Digital Library’s community of users and/or the specific requirements related to its Content. This concept is fundamental to characterise the Digital Library universe because it captures the facilities offered by the overall Organisation.

Policy
The Policy concept represents the set or sets of conditions, rules, terms and regulations governing every single aspect of the Digital Library service including acceptable user behaviour, digital rights management, privacy and confidentiality, charges to users, and collection formation. Policies may be defined within the Digital Library, be superimposed by the Institution establishing the Digital Library, or outside of that (e.g., Policy governing our Society). Policies can be extrinsic or intrinsic. Defining new policies and re-defining older policies, is part of the policy-related functionality that must be supported by a Digital Library. This concept is fundamental to characterise the Digital Library universe because it captures the rules and conditions regulating the overall Organisation.

Quality
The Quality concept represents the parameters that can be used to characterise and evaluate the overall service of a Digital Library encompassing every aspect of it, i.e. Content, User, Functionality, Policy, Quality, and Architecture. Quality can be associated not only with each class of content or functionality but also with specific information objects or services. Some of these parameters are quantitative and objective in nature and can be measured automatically, whereas others are qualitative and subjective in nature and can only be measured through user evaluations (e.g., focus groups). This concept is fundamental to characterise the Digital Library universe because it captures qualitative aspects characterising the Organisation.

Architecture
The Architecture concept refers to a Digital Library System and represents the mapping of the overall service offered by a Digital Library, and characterised by Content, User, Functionality, Policy and Quality, on to hardware and software components. There are two main reasons that make Architecture a core concept:

• Digital Libraries are often assumed to be among the most complex and advanced forms of information systems (Fox & Marchionini, 1998).
• Interoperability across Digital Libraries is recognised as a major challenge. A clear architectural framework for Digital Library Systems offers ammunition in addressing both of these issues effectively.

This concept is fundamental to characterise the Digital Library universe because it captures the systemic part of the service offered by the Organisation.

These concepts share many similar characteristics and they all refer to internal entities of a Digital Library that can be discerned in the outside world. A higher level concept is also introduced, referring to all of them, that is, Resource, which enables us to reason about the common characteristics in a consistent manner. The following summary serves to put the main concepts into perspective.
The Organisation concept surrounds and subsumes all the other concepts. Among the other six concepts, two are independent of each other, in that they exist independently of a specific Digital Library. These are User, which represents external human beings or the hardware interacting with the Digital Library, and Content, which represents the material handled by the Digital Library. Architecture, which is the technological design underpinning Digital Library System, represents the underlying technology that implements all the rest. On top of these concepts there come Functionality, primarily representing the means for connecting User to Content, that is, all procedures, transformations, actions and interactions that bring Content to User or vice versa. Finally, operation of the Digital Library and activation of its Functionality are based on Policy and aim to achieve a certain level of Quality.