Hypertext systems have not yet been accepted as fundamental tools for the augmentation of human intellect since most of them are "insular, monolithic packages that demand the user disown his or her present computing environment to use the functions of hypertext and hypermedia." [Meyrowitz, 1989]. Similar to the "cut and paste" paradigm in windowing environments, linking functionality must become an integral part of the computing environment. Application developers must be provided with tools to enable all applications to "link up" in a standard manner.
Most current hypertext systems are closed systems - material created in one system cannot be transferred or integrated with material created in another system because of proprietary document formats and storage mechanisms. Conversion programs are difficult to write since the formats are not disclosed by organizations [Fountain et al., 1990].
In order to make systems open and also integrate hypertext functionality into the desktop, researchers have been working on various hypertext models and interchange standards. This chapter explores these models and standards:
Hypermedia systems have been closed systems with proprietary storage mechanisms and very little or no interoperability. A number of layered architectures, models or engines, and frameworks have been proposed and developed by researchers in an effort to make hypertext systems more generic and integrated into the desktop environment. Application development toolkits have been developed to assist programmers in adding hypertext functionality to existing systems. In order to make hypertext systems fully open and integrated, the following issues must be addressed: interoperability, programmability, node and link typing, distributed linking, concurrency control for multi-user access in a shared environment, maintaining public and private links, operating systems support, networking, bridge laws, linking protocols, multimedia support, operating systems support, user interface consistency, and version control [Malcolm et al., 1991]. Most of these requirements can be addressed using object-oriented techniques [Lange, 1993].
In order to make hypertext systems fully portable, existing document standards such as ODA and SGML must be extended to support unstructured documents and linking. International standards such as HyTime and MHEG are emerging to support hypertext functionality and multimedia information in applications. Only when hypertext functionality becomes an integral part of our computing environment will knowledge workers accept and incorporate hypertext into their daily work process.