Early hypermedia systems are now referred to as closed systems due to their reliance upon proprietary document formats, embedded links, monolithic designs and their inability to integrate with the desktop environment. Advances from the research community gave rise to a new generation of open hypermedia systems. Open hypermedia systems tend to have modular architectures and can offer an extensible hypermedia link service integrated with the desktop environment. One explanation for the unmitigated success of the World Wide Web (WWW) is the way in which common Internet services have been integrated. Although the WWW is open in terms of the platforms and protocols supported, it has several limitations in common with closed hypermedia systems. Described in this thesis is Microcosm TNG, a framework for distributed open hypermedia, able to integrate with both the desktop and the Internet. The abstraction of a hypermedia application is introduced for improving the organisation and the encapsulation of related documents and link services. Such a resource can then be made available to remote users via the Microcosm TNG framework. Architectural extensions to the system are described which enable the hierarchical composition of hypermedia applications to construct rich distributed information spaces.