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2. User-oriented and task-driven system design
I propose that the design of interactive systems in general should adhere to the following five requirements:
(1) User-oriented design. One should take into consideration the limits and the capabilities of the human information-processing system when designing features and mechanisms of human-computer interaction. This concerns primarily the design of the user interface. It is important to have potential users participating in the design process.
(2) Task-driven design. Even a very user-friendly system is worthless if it does not provide the extent and quality of performance necessary to solve the problems that are part of accomplishing the overall task. A detailed analysis of the task and the corresponding activities is required in order to decide on the kind of support needed by the user and then provided by the computer system.
(3) Theory-model guided design. To achieve usability and utility, it is necessary to have an adequate model of the different processes and knowledge structures involved in the problem-solving activity of the user. I propose that these models be based on cognitive theories of human behaviour.
(4) Empirical-based design. The use of models and theories implies the use of empirical investigations to test and validate the theoretical assumptions and their applicability. This implies rapid preparation of prototypes for testing the ideas with users and engaging in a step-by-step design process.
(5) Technology-knowledgeable design. One has to keep in mind the role of available technology for building systems. At a given point in time, the state of the art of technology and computer science will always constrain the actual implementation. On the other hand, innovations in technology can serve as a source of inspiration for new applications in different domains. Beyond this, it has been argued  that it should be a goal to progress conceptually one step ahead of existing technology and provide requirements to be met by future interactive systems on the basis of cognitive and social theories of human behaviour.
These requirements are statements about the approach. We have also de rived a number of design principles. Here, the principle of "cognitive compatibility" is central [24, 25]. This requires minimizing the discrepancies between the mental problem representations the user forms or has formed about the task and - on the other side of the user interface - the presentation and the function of objects and operations available to the user that are determined by the system's representations.
3. SEPIA: A cooperative hypermedia authoring environment
In this section, I will describe how my ideas that the design and development of interactive systems can and should be based on theoretical considerations and empirical results in the field of cognitive science were reflected in the research and development strategy for SEPIA (Structured Elicitation and Processing of Ideas for Authoring). SEPIA and its basic design principles were first described in Streitz et al.  but did not include the cooperative aspects.
3.1 The R&D Strategy for SEPIA
Our R&D strategy that addresses the cognitive processes, the product, and the social aspects of the authoring activity is characterized in figure 1, showing the relationship of the activity under investigation, the theoretical basis, and the resulting components of SEPIA. Paying attention to the process aspect requires developing and refining a model of the cognitive processes of writing and transforming these results into requirements, as in our activity space concept. Looking at hyperdocuments as a product with features of a new rhetoric [15, 31] results in requirements for a corresponding performance, e.g. our construction kit in the rhetorical space. To get valid requirements, we built a large hyperdocument in a separate reading environment testing our assumptions about a new rhetoric for hypermedia . Considering that most large and complex documents are prepared by a team, social cooperation models had to be defined, and SEPIA was extended from a single-author to a multiple-author environment by providing corresponding cooperation modes. Thus, detailed knowledge about the process, the product, and the social situation played equally important roles in the development of our hypermedia authoring environment.
3.2 The Authoring Activity
While publishing is communicating knowledge, authoring, and in particular writing, is knowledge production and transformation. From our point of view, writing is a complex problem-solving and design activity with multiple constraints. The final product - in terms of a hyperdocument - can be viewed as an externalized representation of internal knowledge structures that have been developed by the author. Thus, authoring tools that are especially geared to hyperdocuments offer much better facilities for conveying the message and intention of authors: authors can externalize knowledge in a format that is closer to their knowledge structures than was possible with traditional linear documents. Making additional properties of the author's knowledge structure (as part of the hyperdocument) available to the reader facilitates integration rather than delinearization and thus more comprehensive processing on the recipient's side. Documents produced with these tools keep authors' knowledge structures alive by preserving, e.g., their argumentation and theoretical structures, which can be used for subsequent processing. This improves reception not only by human readers but also by text analysis components for machine translation or automated abstracting. While it is difficult today to have an adequate analysis of natural language text beyond the sentence level, such hyperdocuments would contain more of the necessary structural information and facilitate the analysis process. Figure 2 shows the differences between the linear and non-linear document structures in the process of communicating knowledge.
Figure 1 Research and development strategy for SEPIA
Figure 2 Communication of knowledge structures
3.3 The Role of Cognitive Theories for the Design of Authoring Systems
The construction of writing tools is mainly based on intuition and first-order task analysis. What is lacking is a sound theoretical foundation for building cognitively compatible interfaces that provide intelligent support for writing. Kintsch  forecasts that progress in this field will remain restricted unless a sufficient cognitive theory of writing is developed. We still do not know what is going on in authors' minds when they progress from "chaos to order," as Brown  has characterized this process.
Based on an analysis of the cognitive processes of writing [1, 11, 10], authoring can be characterized as a "journey of discovery." On this journey, ideas are not merely translated into text ("knowledge telling"); they are also generated and refined, because the production of words and phrases triggers new associations ("knowledge transformation"). The widely cited model of Hayes and Flower  emphasizes the problem-solving aspect of writing. Based on the analysis of thinking aloud protocols, it identifies three main sub-processes (planning, translating, and reviewing). A model that reflects fundamental differences between novice and expert writers has been proposed by Bereiter and Scardamalia . Knowledge transformation is conceived as an interaction between two problem spaces: the "content space" and the "rhetorical space." While the content space is the space of generating and structuring the author's knowledge about the domain of the intended document, the organization of the document structure and the final editing take place in the rhetorical space. This is also where decisions are made on including, excluding, sequencing, and reformulating information. The interdependencies of extensive planning, production, and revision activities are characteristic of the writing process and lead to both an external product the text - and an internal product - a new knowledge structure.
3.4 Supporting the Authoring Process via Activity Spaces
On the basis of research writing, we distinguish three closely related sub-problems that an author must solve to produce a document: (1) the content problem, (2) the rhetorical problem, and (3) the planning problem.
According to Newell and Simon  and Newell , the mental representation of these three problems can be described in terms of separate but interacting problem spaces formed by different constraints, objects, and operations in which different knowledge sources are brought to bear .
Applying the principle of "cognitive compatibility" , we can use this decomposition into sub-spaces as a basis for dedicated requirements of components of the authoring environment. We require that these (cognitive) problem spaces be "matched" in SEPIA by corresponding activity spaces (see figure 3). Each activity space provides specific objects and operations to facilitate the author's activities when working on these sub-problems. Since argumentation is a crucial cognitive activity that plays an important role in writing for a large number of document types, these three spaces are supplemented by a fourth called "argumentation space."
We derived specific requirements for the design for SEPIA from models of authoring. On the basis of these considerations, we determined the characteristic features of the user interface and the functions. The resulting "conceptual interface" is depicted in figure 3. Subsequently, we implemented these ideas. The result is shown in figure 4 as a "screen dump" of the SEPIA environment. Figure 4 presents details describing objects and functions of each activity space. (Note: the order of these descriptions does not mean that an author must use the spaces in that sequence.) a domain model. This can also involve access to background material from either internal (e.g., previous documents) or external sources (e.g., querying a database). Therefore, SEPIA uses the structuring facility of hypertext to support collecting ideas in textual and graphical nodes, their grouping in topic-related clusters by composite nodes, and connecting them via typed links.
Objects and operations of the content space facilitate the development of
Figure 3 The conceptual user-interface of SEPIA
Figure 4 Screen dump of the implemented user-interface of SEPIA
In the rhetorical space, the author creates the reader-oriented, final document. To a large degree but not exclusively, it is produced on the basis of transformations of the material in the content space. This final product can be either a conventional, linear text or a hyperdocument, formed by a typical network of nodes and links. Together these document types constitute a scale reaching from strictly linear to strictly non-linear documents. Hyperdocuments can vary in the degree of their linearity between these two endpoints and can be very different with respect to their structure and presentation. Nevertheless, they all should satisfy one major requirement: in order to support comprehension and navigation on behalf of readers, they must appear as coherent entities. Therefore, the rhetorical space provides a construction kit consisting of objects that are explicitly tailored to fulfil this requirement.
In the planning space, the author is able to externalize his writing plans with respect to goals, construct issues to be concerned with in the document, and establish an agenda of the authoring activity. Consequently, this space serves as a meta-space for coordinating the activities in the other three and controlling the progress of the design process. The formulation of issues may lead to
- the identification of important topics that are elaborated in the content space;
- the generation of positions and claims that have to be supported in the argumentation space; and
- the structuring of the document in the rhetorical space.
For the development of an issue structure, the author can rely on a set of dedicated nodes and links. Here, we use a modification of the IBIS method  by extending the definition of the issue concept and introducing a new principle for linking issues [18, 17]. In addition, the planning space is linked to the argumentation space. Positions that are formulated as answers to issues in the planning space are transformed and re-created as claims in the argumentation space prompting the author to provide supporting documents.
The argumentation space supports the development of an argumentative structure by providing appropriate design objects and operations based on an extension of the well-known argumentation schema developed by Toulmin . Using the argumentation space, the author can elaborate an argumentation by generating support or objections on different levels, by formulating contradictions, and by constructing argumentative chains (for details, see Streitz et al. ).
When "travelling through activity spaces," the author does not need to follow a predetermined route. At every point in the authoring process, he can decide which sub-space to use next. In every sub-space, he can externalize intermediate results, generate new ideas, and revise earlier decisions. To guarantee such high flexibility, it is necessary to facilitate the interaction and smooth transformation of knowledge between the different activity spaces. In SEPIA, this is accomplished by the automatic transfer of objects between specified spaces, their reuse, and indication and control of references between activity spaces.
Beyond the structural aspects, hyperdocuments are very much characterized by the type of media that is used. In general, all atomic (content) nodes carry multimedia information, including text, graphics, pictures, and sound. Currently, we are working on the integration of video as the content of a node. This way of using multimedia capabilities, i.e. as part of nodes and in combination with other media, has to be distinguished from using them for communication purposes as, e.g., in audio and video conferencing systems (see 3.5).
3.5 Supporting the Social Process: From One Author to a Group of Authors
Considering that especially large and complex documents are prepared by a group of authors, our system should be able to support the social processes involved in team work. For this reason, we had to develop social cooperation models and extend SEPIA from a single-author to a multiple-author environment by providing corresponding cooperation modes.
First of all, authors have to be able to access and modify shared hyperdocuments concurrently. If authors want to work on the same part, they have to be prevented from destroying each other's work. In most cases, the overall task is divided into sub-tasks that are assigned to specific authors or subgroups of authors. The authoring environment should support this division of labour. This is facilitated by the modular structure of hyperdocument networks and accomplished by introducing the notion of "composites," which allows a set of nodes that belong to one sub-task to cluster.
We distinguish between the following three modes of collaboration: individual, loosely coupled, and tightly coupled work. These modes differ in the extent of awareness each author has of the activities of his co-authors. In individual work mode, authors communicate via annotations that are reached by each other subsequently. In loosely coupled mode, several authors can work on the same subtask and manipulate nodes in the same composite but not the same nodes. In tightly coupled mode, authors share the same view of the structure of the network and - if they want to - the content of the same node. In this environment with "shared screens," they have full WYSIWIS (What You See Is What I See). Communication and coordination are facilitated by "teleprinters," which are cursors with the names of each author attached so that each one knows who is pointing at which object. But additional communication channels are needed. SEPIA provides a digital audio channel (via the ethernet) for audio conferencing only, as well as a desktop audio/video conferencing device that enables (currently two, but soon up to four, authors) to see and talk to each other using a separate in-house video net. Furthermore, a shared white board called WSCRAWL  has been integrated for the exchange of mete or additional information. It is a group-aware, colour, pixel-oriented, shared drawing tool. Permanent telepointers support gesturing on the whiteboard. Each drawing is immediately visible on all connected screens.
The awareness of the co-authors' activities is a prerequisite for smooth ad hoc transitions from one mode of collaboration to another. Currently the transition from individual work to loosely coupled work is triggered automatically when a second author opens a composite node already "occupied" by the first author. Each author is notified by a "doorbell" sound. The first author then knows that someone has entered his composite and the second author is aware that he has entered where somebody else is working. The status linen of user names displays who is currently in this composite node. There is no limitation to the number of authors in one composite. Being in loosely coupled mode, the various awareness-producing means can cause a need for authors to have a tightly coupled session. To start a tightly coupled session, one co-author selects all or a subset of those co-authors currently in the same node to have them join the session. The system asks each of them to confirm if they agree or not. Then, the browsers of those co-authors who confirmed are shifted into tightly coupled mode. The request for confirmation is necessary because this mode constrains the freedom of each one by imposing strict WYSIWIS in this browser. This implies, e.g., if one author scrolls up in the browser of this composite, all other coupled browsers do the same and the network is moving. Or, if one author opens the content of a node, the content is displayed on all other coupled browsers. On the other hand, this is necessary if authors want to discuss details and be sure that each participant sees exactly the same thing. Authors can exit a tightly coupled session either by closing the composite node or returning to loosely coupled mode.
For more details, especially on the system architecture and the implementation of SEPIA, I refer to Streitz et al. . For implementation details of the database support, see Schütt and Streitz , and for the group-work facilities, see Haake and Wilson .
I presented the hypertext and hypermedia as a powerful concept for the creation, structuring, and presentation of information. In a second step, I introduced the approach of user-oriented and task-driven system design. Building on this, I described the application of cognitive theories of human information processing for the specification of design requirements for a hypermedia authoring system. And finally, I described the user interface and the functions of the authoring environment for one author as well as multiple authors. Reviewing my three claims from the introduction, I can state that my experience in following this approach has been very positive. I do not think that another concept of information structuring would have been as appropriate as the hypertext concept. Its inherent opportunities for modularity, flexible decomposition and combination, reuse of existing material, guided tours, group-specific views, annotations, clustering of information, graphical presentation, and navigation of document structures are what is needed for the complex task of authoring large documents in teams. There is still one aspect missing. We finished building the prototype system only recently. The task ahead is to provide the system to a group of real users outside the laboratory and have them use it. Their feedback will be important for the evaluation of our design decision and their implementation. Based on this information and our own use and thinking, we will review our decisions, redesign this prototype, and produce a new version - as the idea of an iterative design presented in section 2 requires.
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Personal hypermedia systems
2. What is hypermedia?
3. Hypermedia products
3. How useful is hypermedia for business people?
4. Executive information systems
The paper discusses hypermedia technology applications as navigation tools, drawing on many media, for information seeking on personal computers. Stress is given to the tools designed for people without extensive technical background. The Hypertext and Multimedia softwares widely available at PC stores are surveyed, as are Personal Information Manager and Executive Information Systems softwares and Outlining aids.
It is often said that we are in an era of an information flood. l here is much information around us and we do need an efficient way to use it for our everyday activities. For example, we read a newspaper every morning, and there are many pages in a newspaper, even on a usual morning without any big news; but not all the pages are of interest to us: we are interested in some topics. The contents of a newspaper are the source data and the specific topics we are interested in are information. It can be said that data become information when they are evaluated by us as useful or meaningful. So, I should say that we are in an era of a data flood and that we need an efficient way to navigate and to evaluate data in order to reach the useful information.
Businesses depend on organizational structures to filter and evaluate data into information. On each level of hierarchical organization, there are people who have the experience and the professional background to analyse and evaluate data and to obtain information for their own and their colleagues' activities in the company. They use varied office equipment to collect, store, and analyse data. This includes copying machines, electronic filing machines, computers, etc. They also use diverse software to keep data in a systematic way and to retrieve, analyse, and evaluate data. Even those persons who have insufficient experience or professional knowledge can expect to get help from these intermediaries around them in a company.
The information flood is also a big problem for ordinary people, who can not expect much help from intermediaries. Even in a company setting, there may be many people who cannot expect help of this kind, as is the case in small companies or in certain departments of larger companies.
Hypermedia is an information technology that can help individuals navigate through the flood of data and reach the useful and meaningful information with little or no help from intermediaries.
I would like to survey in this paper hypermedia tools designed for people who have no technical background. I would like to survey hypermedia products for the personal computer that are available at local shops at a reasonable price. Anybody who owns a personal computer can use these hypermedia tools when they want to try by themselves. Of course, at research centres or laboratories, they are conducting advanced research for innovative hypermedia tools for the next century, but we cannot try them by ourselves today. The theme assigned to me is "Personal Hypermedia Systems," and I understand that my role is to identify those hypermedia systems for ordinary people that are commercially available at present.
2. What is hypermedia?
Hypermedia is an extended concept of Hypertext. Hypertext is a software tool that establishes links among blocks of data stored on a computer. We can navigate through the data jungle by passing the links of data. The concept of Hypertext came from the creative work of V. Bush, T. Nelson, and D.C. Engelbart. Software products that reflect the Hypertext concept were released for Apple Macintosh in 1986 and 1987. They are Guide (developed by P. Brown at Kent University, United Kingdom, and released by Owl International, Inc.) and HyperCard (developed by B. Atkinson and first released by Apple Computer and now by Claris Corporation).
Macintosh is well known to many users for its GUI (Graphical User Interface) and was selected as a first platform for the realization of the Hypertext concept. But, in IBM-PC, which is much more widely used in business, Microsoft's Windows environment is now rapidly becoming popular, and there are also a couple of Hypertext tools for IBM-PC. Windows gives us a similar GUI environment and is also a good environment for Hypertext because it has multitasking, multi-window systems and data transportability among its applications. Windows has already been installed on more than 10 million PCs. Now, Guide has a Windows version, and Toolbook (Asymetrix Inc.) gives us similar capabilities on HyperCard in a Windows environment.
Computers have been used to process numbers, text, and graphics; and now they can also process image, audio, and movies. This variety of data presentations (called media) has called for a new word, multimedia. In order to be processed by computer, images, audio, and movies must be digitized and they require much more storage space and much more speed to be processed efficiently for practical use. The amazing evolution of information technologies makes it possible to use Multimedia even on personal computers. Now, many products are available for Multimedia, like the digitizing board, the image-capturing board, the scanning machine, the data compression and decompression board(chips), the high resolution colour display, the graphics accelerator, etc. And mass storage devices like CD-ROM drives, optical storage devices, computer supported VCR, and Laser Disk, etc., are available even at the street corner PC shop.
Since the evolution of hardware for Multimedia, many softwares have been released that can process image, audio, and movies in addition to text, numbers, and graphics. For example, word-processing softwares now can show pictures and movies on a page among texts, and spreadsheet softwares can also show pictures and movies on a worksheet and can paste audio annotations on a specific part of a worksheet.
Typical Hypertext softwares like HyperCard and Guide can process Multimedia. They can store images, audio, and movies in addition to text, numbers, and graphics as a block of data and link them. We can navigate through the hierarchy of a data block composed of text, numbers, graphics and pictures, audio, and movies. The Hypertext concept is now extended to include Multimedia and there appears a new word, Hypermedia. Hypermedia is a software that can link blocks of data that are composed of text, numbers, graphics, pictures, audio, and movies on a computer storage device. We can navigate through these various data media to get meaningful information. I am interested in the use of Hypermedia by business people, but in order to get a clear understanding of Hypermedia, I would first like to survey Hypermedia software products in general.
2.1 HyperCard and Guide
HyperCard uses cards of a fixed size to store data. A card can include text, numbers, graphics, pictures, sound, and now even movies. Several cards that share the same framework and purpose make a stack called Hyperstack. We can develop our own Hyperstacks but there also exist numerous hyper-stacks for specific purposes like an address book, an appointment book, etc. Cards in a stack can be linked to each other and can also be linked to cards in other stacks. There are items called objects, such as "background," "field," "button," etc., on a card and cards are linked by those objects.
Figure 1 shows a card that is going to be linked to another card by button. Button information shows where we link the object on a card. We can link objects to outside equipment like CD-ROM, VCR, etc. Hypercard is a general purpose tool and is also flexible.
Figure 2 shows an example of Hyperstack named Symphony #9 from the Voyager Corporation. It allows us to enjoy listening to Beethoven's symphony with the guidance of a music expert. As you see in the figure, it shows music scores and the buttons at the right are linked to the sounds on a CD on a CD-ROM player connected to the PC by a special language script called Hypertalk and XCMD built in the buttons. It also shows a menu from which we can access notes about many items such as cello and chorus that again link to specific parts of the CD where we can listen for example to cello playing or choral singing. The buttons at the bottom are linked directly to other cards and by using arrows we can move forward or backward.
Guide is another Hypertext software for Macintosh and Windows. Guide has four types of linkage. They are Note link, Replacement link, Reference link, and External link. We open a window, where we can type any text, paste any graphics and images, or paste buttons from a button library. These texts, graphics, images, and buttons can be linked to the four types of links. Figure 3 shows the words "Note link" in a text that is going to be linked to a note link. Note link pops up another window while we click the note-linked object. Figure 4 shows the popped up window that is linked to the word by Note link. If we link a Replacement link to an object, then when we click the object, it is replaced by the linked window. Reference link takes us to another window linked to it when we click the object in a window. External link invokes a script written by a special programming language called LOGiiX and performs a specific task like playing a specific part on CD-ROM or starting another software like spreadsheet software to show a graph based on specific data.
I have surveyed two original Hypertext softwares. Their most important function is linking data. Next I would like to show a little about a recent development in multimedia. It is the motion picture and QuickTime done for Macintosh.
2.2 Movie Files and QuickTime
Apple has released for consumer products a new protocol named Quick-Time. It is a protocol for a data file with a time dimension. The most revolutionary application is for movie files. Movie files have a sequence of pictures to be viewed at a specific time interval, e.g. 1/30 of a second. Any Quick-Time file can be played on any QuickTime compatible machine without additional hardware. It can be cut and pasted between different softwares. QuickTime also supports various data compression schemes.
The number of QuickTime compatible softwares and hardwares is increasing rapidly. Figure 5 shows the desktop of Macintosh, where there is displayed World View (a CD-ROM software that includes many professionally prepared movie files) and a program named Screenplay (SuperMac Inc.). With ScreenPlay, we can play movie files on a window. Figure 6 shows a sample frame from Shuttle Liftoff from World View. There are several buttons at the bottom of the window by which we can play, rewind, and forward the movie.
One can buy a collection of movie files (called "movie clips") and view them using the QuickTime compatible software. HyperCard is now QuickTime compatible and Guide for Macintosh will become compatible in the near future.
Apple is now planning to make a QuickTime protocol for Windows as well. But soon we may also feel the need for our own movie files for our own purposes. Recently, there appeared several special boards by which we can easily digitize movies captured through a camcorder.
Figure 7 shows the Screenplay window playing a movie I made last January in Tokyo using a camcorder on a day when we had a lot of snow. It is a short movie that lasts only 12 seconds, but it takes 2.6MB to store the file.
After obtaining movie files, we will use them on a QuickTime compatible software. I tried to paste the movies on a presentation software called Persuasion (Aldus Corp.). I typed several topics on a slide and then imported two movie files on it. Figure 8 shows the slide and we can see movie files of "Shuttle Liftoff" and "A snowy day in Tokyo." One of the movies has a pull down menu with the Play command. We can see movies on the slide if we click the play button.
Multimedia is becoming accessible for everyone through this kind of technological development. There are already many products that have some kind of linking function and include multimedia such as pictures and sounds. I will survey several of those Hypermedia products.
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