Digital libraries are concerned with the creation and management of information sources, the movement of information across global networks and the effective use of this information by a wide range of users. A digital library is a vast collection of obj ects that are of multimedia nature, e.g., text, video, images, and audio. Users wishing to access the digital library objects may possess varying capabilities, preferences, domain expertise, and may use different information appliances. With the phenomenal growth of the Internet, the number of different information appliances will, if not already, increase substantially in the near future. Facilitating access to complex multimedia digital library obj ects that suits to the users' requirements is known as universal access.

The main objective of this thesis is to present our research work in the area of Universal Access within digital library environment. In this thesis, we will first present the current and future trend in information appliances, followed by discussion on the scope of our work. We propose an object manifestation approach in which digital library objects automatically manifest themselves to cater to the users' capabilities and characteristics. We provide a formal framework, based on Petri nets, to represent the various components of the digital library objects, their modality and fidelity and the playback synchronization relationships among them. We develop methodologies for object delivery without any deadtime under network delays. We have implemented a working system prototype to realize our approach.