|
|
|
|
|
|
|
Hypermedia is basically a hypertext in which other media such as sound, graphics, animation and even video have been added. Different authors, however, define it in different ways. Park (1991, 26), for example, states that "hypermedia are software systems integrated with the structural characteristics of a data base management system, a psychological approach for representing knowledge and a technical method for supporting human-computer interaction processes". Marchionini (1988, 8) states that: The term "hypertext" describes the electronic representation of text that takes advantage of the random access capabilities of computers to overcome the strictly sequential medium of print on paper. "Hypermedia" extends the nonlinear representation and access to graphics, sound, animation, and other forms of information transfer. Boone and Higgins (1991, 21) give a similar definition. They state that the terms "hypertext describes the concept of non-sequential text presentation. ... hypermedia, correctly designates a hypertext document that includes graphics, digitised speech, music or video segment". Obviously, by both name and definition, the non-textual elements of hypermedia are important, and from the instructional point of view, hypertexts and hypermedia would present their own unique advantages and disadvantages. The use of the non-text media bring with them extra considerations which have to be taken into account when preparing hypermedia CBI and it is assumed that they make the instructional materials far more effective. In view of this, it was extremely disappointing to find that the vast majority of writers and researchers used hypertext and hypermedia synonymously and dealt only with hypertext issues; no discussion was encountered about the effective use of the other media. Some rather startling claims about hypermedia were made in the literature. For example, Park (1991, 28) states that: Some researchers (e.g., Fideria, 1988; Jonassen, 1986) argue that hypermedia is a mechanism to externally represent the active structural network of human cognition (Quillian, 1986). In this argument, nodes in hypermedia are devices to represent schema in the user's cognitive structure. Links are said to represent the semantic relationships among the schema. Marchionini (1988, 8) also states that: Proponents of hypermedia systems claim that these systems model human associative memory and thus can serve as powerful cognitive amplifiers It is difficult to understand how it can be claimed that knowledge can be structured in a hypertext in a way which represents its structure within the memory when Morariu (1988, 17) states that "The truth is that psychologists are not quite certain of how information is organised in the mind". Jonassen (1988, 13) states that, according to the Schema theory, learning involves the construction of new nodes and creating links with existing ones and that the more links that can be generated between the existing and the new knowledge, the better it will be comprehended and the easier learning will be. Learning, according to Jonassen "is conceived as a reorganisation of the learner's knowledge structure" and: In Piagetian terms, learning is the assimilation of the teacher's knowledge by the learner and the reorganisation of the learner's knowledge structure to accommodate that new knowledge. That means that during the process of learning, the learner's knowledge structure begins to resemble the instructor's. ... Learning may be conceived of as the mapping of subject matter knowledge (usually that possessed by the teacher or expert) onto the learner's knowledge structure (Jonassen 1988, 13). Jonassen (1988, 14) then considers hypertext in the light of this concept of learning. He argues that with normal text, the reader is forced to read the information in the sequence determined by the author and that this sequence is dependant upon the knowledge structure of the author. With hypertext, however, the reader can access in any order. He suggests that the user may access information from a hypertext document based on various criteria including the personal relevance of the information to the user, the user's interest level, experience, and the task for which the user accessed the hypertext. He continued: In hypertext, readers are not constrained by the subject matter structure or by the author's organisation of the text. Since an individual's knowledge structure is unique, based on his or her own experiences and abilities, the ways that individuals prefer to access, interact with, and interrelate information is also distinct. In order to accommodate the text to the learner, rather that the learner to the text or its implicit structure, the text structure should be under the control of the learner. In order to get the most from accessing information, learners should be encouraged to explore information and even alter it in ways that make sense to the learner. Hypertext permits these activities (Jonassen 1988, 14). While this last statement is the one usually put forward by proponents of hypertext and hypermedia, it seems to be opposed to the previous one which suggested that during the course of instruction, the learner's knowledge structure beginning to resemble that of the teacher. If this is regarded as being a desirable process, then a lesson or written material would appear to be more appropriate as the teacher's knowledge structure can be more accurately mapped in this way than by using hypertext which gives the learner a great deal of freedom. However, it could be questioned as to how closely the student's knowledge structure could come to resemble that of the teacher. The two would have different experiences, motivations, and levels of overall knowledge. In view of this, it could be argued that an advantage of hypertext and hypermedia is that they do not impose the knowledge structure of a teacher upon students, rather they are allowed to construct their own. Hypermedia contains links between various nodes, but the question can be raised as to who should have the control over these links. Park (1991, 24) suggests that the users should be able to create links and also nodes to store additional information and comments. This could become a very difficult situation to manage if the hypertext or hypermedia system is shared over a network as it would be necessary to personalise the changes so that they were only apparent to the individual who created them. This concept was partially introduced into Intermedia, a hypermedia system produced at Brown University's Institute for Research in Information and Scholarship (IRIS) (Landow 1989, 40). This system was demonstrated at the Pacific University Consortium Conference (Woolongong, 1989) and is also described by Yankelovich et al. (1988, 35-85). Unfortunately, the system has been discontinued due to problems with the operating system (Cunningham, pers. comm., 1992). Using Intermedia individual teachers could establish links for their students to follow, but these would not be seen by other students. In addition, students could create paths for the teacher to follow as part of their assignment work. This system, however, illustrated a major problem that will have to be faced by the designers of large hypertext or hypermedia systems, copyright. For a very large system to be generated, non-original material must be used as there would be insufficient time to research, write and enter original material. A problem arises if the system is to be sold. A purchaser of Intermedia could only obtain the application and a small amount of the corpus of information. The result of this is, unless the copyright system is amended, each institution will have to enter their own information into the system, thus limiting the amount of information that they contain, and preventing the sale of complete systems thus depriving the institutions from recouping development expenses. The ideal situation would be for a system such as Intermedia to be sold to a number of organisations who would add more information to it so that a very large corpus of knowledge would be built up. The current situation is somewhat akin to libraries being sold blank text books and being told to enter the content themselves. A hypertext or hypermedia system typically contains a large amount of information not all of which is relevant to every user. It could be suggested that users could be allowed to create their own personal system. They could copy information from a master system into their own and create their own links within it. In this way, users could create their own system which would meet their cognitive needs. The main problems with this would be the time required to learn how to manipulate the system and the fact that users would have to have a good working knowledge of the master system in order to obtain all the information that they required. Landow (1989, 39-64), using experience gained from working with the Intermedia system, has proposed a series of rules for authors of hypermedia systems. The first of these rules are concerned with maintaining the relevance of links that are created in hypermedia and hypertext systems. In rule one, he argues that users expect a link to be of importance and frustration will result if this is not so. Rule two states that links should be created in such a way that users will be taught "sophisticated critical thinking" (1989, 42). To this he adds rule three which states that if users encounter links which do not appear to bear a significant relation to the originating document, they will also "feel confused and resentful" (1989, 42). He argues that graphics often require more textual information than a brief title if users are to fully appreciate their significance. He states that this is a common mistake that is often made, for example, in textbooks and the result is that readers simply skips over the illustration, but in hypermedia, where the linkages "suggest that the user will encounter significant relationships between materials" ignoring such graphical materials becomes more difficult (1989, 42-43). The second set of rules proposed by Landow (1989, 43-55) concern the problems encountered in navigating through hypermedia. He states that one reason for users of many hypermedia systems becoming lost is that they are not provided with an overview of the materials or with information about where links will take them. Authors of hypertext and hypermedia systems must, according to Landow, ensure that users are aware of the differences in such systems and more traditional informations sources and they must provide ways of stimulating the users to think and explore the systems (rule 4). "User-friendly" navigational aids must be provided (rule 5). Such navigational aids should enable users to determine their present position, the relationship of their present location to other materials, to return to the starting point, and to be able to explore other materials which do not have direct links to the current position (rule 6). Landow (1989, 44-53) claim that the authors of Intermedia have found the solution to the problems encountered by users of hypermedia systems and suggests that other systems should use similar methods of helping users. When starting up Intermedia, users see a 'desktop' which contains a variety of folders containing information about various subject areas. After selecting the required subject-area folder, users are shown a series of overviews and the appropriate one is selected. The material can be explored from this overview and they can be further assisted to move through the system by a web view which is generated by Intermedia. This indicates all documents that are accessible; each one, including the starting document, is represented by an icon which, when clicked, moves the user to the relevant document. Link markers and block descriptors, which are generated by Intermedia are also provided. These provide the user with information about the links available and the contents of associated blocks thus allowing orientation in large areas of the material. Landow (1989, 49) emphasises the importance of overview and gateway documents and states that they should be used by all authors. Overview documents can take a variety of forms and are generated by the author (as opposed to those generated by the system itself) and serve as directories to aid in the navigation of the materials. They assist users to gain access to "all the materials in many documents or to a broad topic that cuts across several disciplines". He also suggests that overviews should be used when there are so many links attached to a particular block that the user cannot evaluate them conveniently. There are six different types of overviews in Intermedia:
Landow (1989, 53) suggests that hypermedia authors should consider employing several types of overviews within their systems (rule 7) Landow's rules 8 to 13 concern links. In essence he says that the users of the system should be aware of where a link will take them and what direction they can take through the material if they follow a specific link. From this, it could be suggested that the following techniques could be employed to assist users:
One problem exists with this and that is, as more assistance is provided to the user, the more skills the user has to develop to access it. With a very simple navigational structure, users can operate a hypermedia with a minimum amount of instruction, but they have the potential to get lost in it. More sophisticated navigational systems reduce the chance of users getting lost but they have to learn more about the system in order to use it effectively. To reduce this learning time, another rule could be proposed, maintain consistency with navigational aids, not only within a particular system but over all the ones that a particular group of users has access to. A further rule would be to design navigational aids so that they can be used intuitively so as to allow users to concentrate on the information contained in the system rather than the system itself. When considering the educational use of hypermedia, it should be noted that there are two distinct types of hypertext/hypermedia applications. The first of these, Guide for example, allows users to enter text and create suitable links, but little else, while the second type such as HyperCard and SuperCard have their own programming languages and so allow for much more complex systems to be developed. Park (1991, 27-28) suggests that there are four main educational uses for hypermedia:
Park (1991, 28-29) states that there are a number of areas where research must be conducted into the educational use of hypermedia. The first of these is the issue of user control. Parks states that many studies have pointed to the ineffectiveness of user control. However, it can be argued that many of these studies, in all probability, would have been conducted using CBI materials that were based on a strong behaviourist philosophy. In the behaviourist paradigm, the teacher is in control of the learning situation and to relinquish any of this control would make the teaching process inefficient. Hypermedia, however, must be based on a constructivist point of view and to remove user control would be counter-productive and, at the worst extreme, would reduce the software to electronic page turning devices. Park (1991, 28) argues that research is necessary for "the selective use of learner-control", however, as learner-control is so central to the effective use of hypermedia, it can be argued that the whole issue of learner-control should be re-examined from a hypermedia-perspective. Park (1991, 29) states that a lot of work has been conducted in the area of the "selection of information-representation forms (e.g., text, graphics, pictures, sound, etc.) but the results have been inconclusive". This problem is compounded by the fact that much of this work has been conducted on media far different from computer-based hypermedia. In view of this, it is argued that the whole situation should be re-assessed in light of this new technology. Until recently, according to Park (1991, 29) the amount of information available to a given CBI program has been restricted by the storage capacity and the processing power of the computer. This situation is now changing and computers will have access to large external knowledge-bases. This will mean that it will be possible for all the instructional material to be accessed from this external source with the CBI program simply giving appropriate access to this material, controlling the presentation and, if required, monitoring the progress of the student. Obviously the development of such a system would require a great deal of research. Park (1991, 29) argues that there are primary limitations to the use of hypermedia in CBI (presumably the problems of navigation and user control), but he suggests that these could be overcome by the production of intelligent hypermedia. Such a system could, for example, monitor the users' progress through the material and, if they got lost, offer advice based on how they had been using the material, their route through it, and so on. A second function would be for the generation of information which would allow content from many different nodes to be combined and presented to users. This would bring the information to them rather than them having to navigate their way to it thus preventing "semantic disconnection problems". The use of an intelligent system could also lead to an natural language interface which would allow the user to ask the computer questions in normal human language (Park 1991, 29). One of the most difficult parts of producing any CBI material is the development of the interaction interface. If the interaction is conducted on the computer's terms it is very restricted and both limits and guides the user by, for example, asking for one of four choices to be selected. If, on the other hand, the interaction is to be on the users' terms, the designer currently has to think of all the possible responses. This is very difficult; for example for a "yes" response, the user could enter yes, yeah, ok, or even 'right on' as well as misstyping any of these responses. The development of a natural language interface would, obviously, overcome these problems. There are two possibly types of such interfaces. The first would be universal in that it would be able to understand virtually every thing 'said' to it and so be applied to all programs. Such a system would take a considerable amount of time to develop and would be very large and complex. A second alternative would be to have an interface specific to a particular CBI program. This would just be able to deal with information about that program, and so would be smaller, less complex and be produced much earlier. The negative side of this is that an interface would have to be prepared for each individual application. While part of the definition of hypermedia includes video, until recently its use has been very restricted as the only convenient source was videodisc. This situation has now changed, however, as Apple Computers have recently released QuickTime. This is part of the operating system which controls time-based applications such as sound, animation and video. Using a suitable video card, video from a camera or VCR can be captured by a Macintosh computer and compiled into 'movies' and replayed from applications such as HyperCard. The basic technology that has enabled this is video compression. A video image is composed of a huge amount of information. Both a television screen and a computer monitor produce an image by either switching on or off a series of picture elements or 'pixels'. On a nine inch Macintosh screen there are 512 by 342 or 175,104 individual pixels. This screen is black and white and so an individual bit is used to switch on a pixel (1) or switch it off (0) and so 21,888 bytes of information would be required to code for an image on it. If the image is colour, however, far more information is required to produce it. If the image is composed of 256 colours, then 8 bits are required to control each pixel which means that 175,104 bytes would be required. If the image was to use millions of colours (a Macintosh is capable of producing 16.8 million colours) then 32 bit per pixel are required which means that 700,416 bytes of information would be needed to produce the same sized image. A PAL television image is produced at a rate of 25 frames per second and so 'real time' television requires a huge amount of information to produce it. While a normal television screen is being constantly re-drawn, a lot of the changes made are, in fact, redundant. Take, for example, the case of a close up of some one talking; the only part of the picture that is changing rapidly is the mouth; the eyes will blink every few seconds and the position of the head may well change every now and then. This means that, if two sequential frames are compared, there is very little difference between them and so, if only the changes in the picture were made, rather than the whole of the frame being completely re-drawn, there would be a massive reduction in the amount of information required. This is one of the methods used in compressing video although it should be noted that the situation is slightly more complex than this, as the whole picture is completely re-drawn after a specific number of frames. Despite the use of compression, a one or two minute QuickTime movie which generates only a small image can become large and require several megabytes of disk space. The file will become even larger if sound is added to it. When an analogue recording of sound is made, the diaphragm of the microphone is vibrated and this causes an electrical current to be generated. The size of this current is then recorded on magnetic tape. When the sound is replayed, the magnetic information on the tape is used to generate an electrical current which is amplified and used to vibrate the cone of a loudspeaker. These vibrations vibrate the air and this produces a sound. Sound that is to be used by a computer, however, has to be stored in a digital form. To do this, the sound is 'sampled' which means that at pre-determined intervals, the amplitude and frequency of the sound are measured and these measurement are stored. When the sound is to be re-played, the only information about it is in the form of these samples, and the computer has to attempt to reconstruct the sound wave from them. The more samples that there are, the more realistic is the sound that is re-constructed, but the file that stores them can become very large. The best quality sound is produced by sampling the sound 22000 times a second, but this results in one second of sound requiring 22 kilobytes of storage. The inclusion of sound, graphics, animation and video increases very greatly the storage overheads required for hypermedia and while the storage capacity of magnetic discs is constantly increasing, their use becomes impracticable for the long term storage and distribution of hypermedia CBI materials. This has generated a need for cheap, large capacity storage media and has brought about an increase in the importance of Compact Disc Read Only Memory (CD-ROM) optical storage. CD-ROMs have the same structure as audio compact discs and some CD-ROM players will also read normal CDs. CD-ROMs hold comparatively large amounts of information (up to about 670 megabytes) comparatively cheaply (approximately $2.50 per disc although it costs about $1,000 to produce a master). While CD-ROMs have the disadvantage of a comparatively slow access time, they are the current medium of choice for the distribution of large hypermedia and multimedia systems. |
|
|
|
|
Footnotes |
|
|
Rule 1. The very existence of links in hypermedia conditions the reader to expect purposeful, important relationships between linked materials. Return |
|
|
Rule 2. The emphasis upon linking materials in hypermedia stimulates and encourages habits of relational thinking in the reader. Return |
|
|
Rule 3. Since hypermedia systems predispose users to expect such significant relationships among documents, those documents that disappoint these expectations appear particularly incoherent and nonsignificant. Return |
|
|
Rule 4. The author of hypermedia materials must provide devices that stimulate the reader to think and explore them. Return |
|
|
Rule 5. The author of hypermedia must employ stylistic devices that permit readers to navigate materials easily and enjoyably. Return |
|
|
Rule 6. Devices of orientation permit readers (a) to determine their current location, (b) to have some idea of that location's relation to other materials, (c) return to their starting point, and (d) to explore materials not directly linked to those in which they presently find themselves. Return |
|
|
Rule 7. Authors should consider employing several overviews to organise the same body of material and to assist readers to gain easy access to it. Return |
|
   |
|
|
Author: Tony Brown Created: 25.6.97 © The University of New England, NSW, Australia |
