Abstract
Digital libraries (DLs) are complex information systems and therefore demand formal foundations lest development efforts diverge and interoperability suffers. In this dissertation, we propose the fundamental abstractions of Streams, Structures, Spaces, Scenarios, and Societies (5S), which allow us to define digital libraries rigorously and usefully. Streams are sequences of arbitrary items used to describe both static and dynamic (e.g., video)
content. Structures can be viewed as labeled directed graphs, which impose organization. Spaces are sets with operations that obey
certain constraints. Scenarios consist of sequences of events or actions that modify states of a computation in order to accomplish a functional requirement. Societies are sets of entities and activities, and the relationships among them. Together these abstractions provide a formal foundation to define, relate, and unify concepts -- among others, of digital objects, metadata, collections, and services -- required to formalize and elucidate ``digital libraries''. A digital library theory based on 5S is defined by proposing a formal ontology that defines the fundamental concepts, relationships, and axiomatic rules that govern the DL domain. The ontology is an axiomatic, formal treatment of DLs, which distinguishes it from other approaches that informally define a number of architectural invariants. The applicability, versatility, and unifying power of the 5S theory are demonstrated through its use in a number of distinct applications including: 1) building and interpreting a DL taxonomy; 2) informal and formal analysis of case studies of digital libraries (NDLTD and OAI); 3)utilization as a formal basis for a DL description language, digital library visualization and generation tools, and a log format specific for DLs; and 4) defining a
quality model for DLs.
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