The Navigational and Cognitive problems of Hypertext and Hypermedia

Abstract

Over the last decade there have been considerable advances in the ways in which information can be stored, processed and delivered. Of particular importance are the developments in computer storage technologies and the various mechanisms by which people can interact with computer systems. These developments enable large volumes of information to be stored and displayed in 'electronic form'. Such information can be organized in a linear fashion or it can be organized into other, more sophisticated non-linear structures. Non-linear arrangement of textual materials is called 'hypertext'. Similarly, non-linear arrangement of multimedia information, a combination of text, images and sound, is known as 'hypermedia' [1,2]. 1.2 Design of Hypertext and Hypermedia Systems Hypertext systems allow the customization of documents in different layers of text in a hypertext document. It means that users can interact with the text at a number of different levels with differing amounts of detail being presented to different users or to the same user at different times. Hypermedia systems allow people to access * Library, Faculty of Science, University, of Colombo, P.O.Box 1698, Colombo 3, Sri Lanka. E-mail: kuruppu@vidya.cmb.ac.lk Vol 6 No 4 October 2000 233 Kuruppilinformation in a sequence, volume, and format that best suits theaf respective needs at the time they aqcess the information. They can change their access strategy each time, according to their convenience [3;4]. Herrstrom [3] noted that hypertext systems are most often designed as webs, which allow users to move virtually from anywhere to anywhere by association. The hypertext network can be regarded as a layered structure, that is, document network and concept network. The concep network is regarded as an index to the documents, as each document i linked in the network to those nodes that represent concepts to which is related [5]. Documents stored in hypertext have active cross-references, J hypertext system is made of nodes and links, allowing for three dimensional navigation through a body of data. A node usuall] represents a single concept or idea and is connected to other nodes bj links. Either the hypertext system designer can predefine the links or th<user(s) can establish the links as part of walking through thoinformatioi space [6]. Both nodes and links can be typed, that is, tagged" in a specifuway, which allows them to be identified individually or as members oa set. Pools of information are collected, labelled and electronicall; stored as nodes in a database. The combination of the nodes and theiconnecting links form a hypertext network and is called a hypergraph. Ellis [4] stated that the implementation of a hypertext documen database is affected by four major issues - authoring versus browsingjmental model and metaphor; search and navigation; data preparatjot(conversion of text to hypertext). 1The database may incorporate both hierarchic and non-hierarchijlinks with different underlying structure being adopted to suit differenapplications. Links can be of two kinds: • Structured link which maintains the underlying skeleton or basistructure of the hypertext, and 234 Information Studii Navigational & Cognitive Problems of Hypertext & Hypermedia • User defined link which allows the user to create new associations in the hypertext. The node from which a link originates is called the reference and the node at which a link ends is called the referent. They are also referred to as anchors. Links can usually be embedded in text and can then be edited and reviewed; links may also have attributes, which may be created, deleted or changed. In addition to their role as connecting points, the system designed as links can be used to • connect a document reference to the document itself; • connect a comment or annotation to the text about which it is written; • provide organizational information; • connect two successive pieces of text, or a piece of text and its immediate successors; and • connect entries in a table or figure to descriptions, or to other tables of figures [7]. In the design of the system, movement from node to node in a hypertext is carried out via links. So, it is essential that the system recognizes the links and can follow them, and that movement between nodes can be done quickly and easily.