5. Hypermedia Systems
In this section I discuss some of the current hypermedia systems. Links and discussion of other systems may be found from CERN: An Overview of Hypertext and IR systems and applications.
A well known hypermedia system is Intermedia developed at Brown Universitys Institute for Research in Information and Scholarship (IRIS) between 1985 and 1990 (see for example [Haan, ACM Comm. Jan 1992]). Intermedia is a multiuser hypermedia framework where hypermedia functionality is handled at system level. Intermedia presents the user graphical file system browser and a set of applications that can handle text, graphics, timelines, animations and videodisc data. There is also a browser for link information, a set of linguistic tools and the ability to create and traverse links. Link information is isolated from the documents and are saved into separate database. The start and end position of the link are called anchors.
World Wide Web (WWW) is a global hypermedia system on Internet. It can be described as wide-area hypermedia information retrieval initiative aiming to give universal access to a large universe of documents [Hug93]. It was originally developed in CERN for transforming research and ideas effectively throughout the organization [Hug93]. Through WWW it is possible to deliver hypertext, graphics, animation and sound between different computer environments. To use WWW the user needs a browser, for example NCSA Mosaic and a set of viewers, that are used to display complex graphics, animation and sound. NCSA Mosaic is currently available on X-Windows, Windows and Macintosh.
5.3. NSCA Mosaic and Netscape
The browser itself can read hypertext documents that are marked with HyperText Markup Language (HTML). HTML is based on Standard Generalized Markup Language (SGML), and contains all formatting and link information as ASCII text. HTML documents can reside on different computers on Internet, and a document is referenced by URL (Universal Resource Locator). URL is of the form http://computer.org.country/doc.html where computer.org.country is the name of the computer and doc.html is the search path to the document. In order to create a node for WWW, a HTTP (HyperText Transfer Protocol) server application is needed. A link in WWW document is always expressed as URL. Links can be references to files in ftp-servers, Gophers, HTTP-servers or Usenet newsgroup.
Netscape is a popular WWW browser developed by Netscape Communications Corp. Netscape 1.1 supports some HTML 3.0 features (tables) and has interesting API, that makes it possible to develop
Documents that are formatted using RTF can be transfered to HTML by using a converter RTFtoHTML. It generates HTML document from the original RTF document and a set of picture files if the RTF document contained pictures. In the HTML document links are created to the graphics files. The graphics can be viewed on most environments if pictures are of type GIF.
Arena is an experimental WWW browser developed in CERN. It supports HTML 3.0 and thus is able to display mathematical formulas and tables.
Recently, The Mathsoft company has announced MathBrowser, a WWW-browser that can display HTML and MathCAD documents. MathBrowser has a computational engine and interface similar than MathCAD, allowing the student to edit MathCAD documents through the Internet. MathBrowser is used to distribute a collection of Shaum's outline series in electronic form.
5.6. HyperCard, Toolbook and MetaCard
HyperCard is hypermedia authoring software for Macintosh computers. It is based on a card-metafora. Hypercard application is called a stack or a collection of stacks. Each stack consists of cards and only one card is visible in a stack. A card is displayed in fixed size window. Hypertext links can be programmed by creating buttons and writing a HyperTalk script for the button.
MetaCard is similar application than HyperCard but it runs in Unix environments. MetaCard offers the ability to create and modify applications using interactive tools and a simple scripting language.
Intrestingly, HyperCard stacks can be imported to MetaCard. However there are some incoptabilities on the HyperTalk and MetaTalk, so advanced stacks dont run without modifications.
LinksWare is a commercial hypermedia authoring software for Macintosh that can create hypertext links between text files created with different word processors. LinksWare uses a set of translators to convert files to its own format (Claris XTND system). This can make the opening of a file very slow. LinksWare can open files that contain mathematical text, but files may be formatted differently than in original document, especially formulae do not appear to have proper line heights. In addition, it can not create links to other applications. However, it can create links to Apple script command files that can open an application and execute commands for that application.
Hyper-G is the name of an hypermediaproject currently under development at the
IICM. Like other hypermedia undertakings, Hyper-G will offer facilities to access a diversity of databases with very heterogeneous information (from textual data, to vector graphics and digitized pictures, courseware and software, digitized speech and sound, synthesized music and speech, and digitized movie-clips). Like other hypermedia-systems it will allow browsing, searching, hyperlinking, and annotation. Like no other big hypermedia system known today, it will also support automatic indexing and link-generation, a variety of automatic consistency-checks, a built-in messaging and computerconferencing system, a special editor allowing the incorporation of animation sequences, question/answer dialogues, and a number of unorthodox man-machine interfaces. Further, and maybe most important of all, it is built on the basis of already existing large databases: hundreds of CAI lessons, a large general-purpose encyclopaedia in hypermedia form, a number of smaller special-purpose lexica, a data-base of thousands of pictures, some pieces of digitized sound and movie-clips, and links to other databases in other networks. A number of smaller spin-off applications are surfacing which are mainly pursued by IMMIS and have led to research in the area of computerisation of various aspects of museums.
5.9. Interactive Calculus Courses
However, there are also whole courses implemented in computer form. A package called Calculus&Mathematica is a calculus course that uses Mathematica notebooks to present theory, examples and exercises. Students can fully access Mathematica by typing in commands in Mathematica language. Each notebook introduces the theory of the topic, which is followed by examples. Calculus&Mathematica contains a special font for the presentation of mathematical formulas.
The Transitional Mathematics Project at Imperial College London has produced similar Mathematica notebooks to be used in calculus courses. At the end of each notebook there is a set of exercises to be solved with pen and paper and evaluated by the computer. Some feedback is provided for the student ("you got 2 out of 4 correct"). Mathematical formulas are created with a special formula editor and transferred to notebooks as pictures.
This kind of material certainly has its place in the classroom. It offers the capabilities of computer algebra systems to students right from the beginning of their mathematics studies. The disadvantage is that students must learn the material in sequental order; it is not possible to choose an individual order of progress. Apart from the possibility to open and close notebook cells, there are no hypertext features in Mathematica.
Until recently only a few courses in mathematics have been implemented as hypertext. One example is "A Simple Introduction to Numerical Analysis". The material is published on a CD-ROM that contains the hypertext material, animations and graphical tools. Another interesting course is a hypertext version of "Introduction to Algorithms". This CD-ROM contains hypertext, several animations and QuickTime movies. These high-quality texts and animations add a new dimension to learning mathematics. To see a sorting algorithm in action gives the user a mental reference or orientation basis to which to relate the theory and implementation of that algorithm.
However, there is a problem related to the way the material is put together. For the reader the material seems to be a collection of cards or stacks that do not form an entity. This problem is partly due to a limitation in HyperCard; HyperCard is not able to treat mathematical formulas as written text. That is why they must be transferred as pictures. HyperCard can present pictures and text only on cards, not on scrollable text fields. The card itself is not in a scrollable window and only one card can be visible at a time. As a result, when a new card is turned on, all the previous information disappears with the old card.
5.10. CAN/RIACA Interactive Book on Lie Algebra
In Amsterdam CAN/RIACA is developing a hypermedia system on Lie Algebra. They also participate in OpenMath development.
5.11. Microcosm (UK)
Microcosm is an attempt to include hypertext functionality into several applications like Microsoft Word and Exel. Microcosm has a dynamical linking facility, ie. it tries to create possible links based on the selection made by the user. Applications are divided as Microcosm aware or simple viewers. Links are saved to separate link database in Microcosm server.
5.12. Mathematical Simulation Environments
Simulation environments are not hypermedia applications as such. However, they are an important part of a hypermedia based learning environment on mathematics and engineering sciences.