[2]The Memex is a hypothetical hypertext engine that was described by Vannevar Bush in his seminal paper "As We May Think". It was to be realized based on microfiches and mechanical links [Bus45].
[3]The Network Audio System was developed by NCD for playing, recording, and manipulating audio data over a network. Like the X Window System, it uses the client/server model to separate applications from the specific drivers that control audio input and output devices.
[4] Instead of the expression "navigation tool" Frisse uses the term "guide" in the general sense of a sign or mark that serves to direct. We will be using the term "guide" later in this paper in the more restricted meaning of a "guide" being a person or agent who shows the way by leading, directing or advising.
[5]Our categorization into 7 design issues treats the information exploration problem on a practical, application-oriented level. The underlying theoretical information retrieval and user modeling techniques have been discussed in the preceding chapters.
[6]Believers in static links.
[7] Vannevar Bush is generally considered to be the inventor of the hypertext idea. He first presented his thoughts in the classical article "As We May Think" [Bus45], where he introduced the hypertext concept with the example of the hypothetical "memex" system.
[8]See chapter 1.
[9]"DOI" stands for "Degree Of Interest".
[10]Microelectronics and Computer Technology Corporation (MCC) in Austin, Texas, is a joint research consortium sponsored by the US industry.
11The HyperCard travel information system "Business Class" was developed by Danny Goodman, author of a best selling HyperCard book, and sold through Activision, Mountain View, CA.
[12]The tool described here is part of a larger European project with the acronym SOUR. SOUR stands for SOftware Use and Reuse.
13As our society shifts towards complete information linkage, we approach the cyberspace society described in the books of William Gibson [Gib84]. We hope that the society we get will be different from the one Gibson describes, but the concept of the tool described in this paper fits well into Gibson's cyberspace, because, as Gibson's electronic agents do, our tool tries to help the reader to navigate in a complex virtual environment without the reader having to understand the inner workings of the tool. Therefore we have titled our navigation tool cybermap.
[14]It is of no importance whether cybermap is applied to a
sequential document or to a hyperdocument. Therefore the terms "document" and
"hyperdocument" are used interchangeably to designate the basic document upon
which cybermap is applied.
Whether cybermap can be easily extended to
multimedia documents is a separate question. The basic algorithm described in
the body of this paper is restricted to textual documents. We have built a
prototype cybermap for a collection of digitized movie segments, but the
generation of the map was based on a textual description of the segments
written by the movie makers.
[15]Of course cybermap can also be used to browse plain (non-hypertext) documents.
[16]It is straightforward to put a node into more than one hyperdrawer. Instead of putting the node into just one hyperdrawer, the node would be placed into all hyperdrawers where the similarity of node and hyperdrawer is above a certain threshold.
17The number twenty may seem somewhat arbitrary and in contradiction to the human user interface guideline of not using more than five to nine different items at the same time. But we claim that nine items are often insufficient to show the structure of a complex document. In our tests we got best results with up to twenty nodes.
18An obvious extension would be to show users also where they have been by marking all read nodes on the cybermap. Some sort of "bread crumb" mechanism [Ber88] has already partly been implemented in cybermap. (See figure I.97 for an example.)
19For a detailed explanation of the fish eye view concept and the DOI-function see chapter 11.
[20]For a full motivation of the use of log2 and inverse document-frequency see [Jon72].
[21]In comparison, processing time for a ten-kilobyte document on a Macintosh IIci is about fifteen minutes.
[22]We will compare the clustering properties of the local tree generation with cybermap clustering in the next chapter.
[23]The Connection Machine needs 5 to 10 minutes (depending on the number of attached processors) to compute a cybermap of the whole bible.
[24]This effect can be corrected to some extent by normalizing the weights of the keyword vector with respect to the number of words.
[25]The misplaced node talks about members of the Islamic Salvation Front being held hostage in primitive detention camps in Algeria. It has been put into a tree about the US presidential elections and White House politics. It is up to the reader to decide whether the misplacement comes from our algorithm or from the nature of US home politics.
[26]Gouraud shading is a computer graphics procedure to get smoothly shaded surfaces of three-dimensional objects. Ray tracing is another process that allows for more than one light source with mirroring of the light sources.
[27]MacroMedia Director is a powerful standalone animations package with a built in scripting language, Lingo. It is based upon the cast, score, and stage movie maker metaphors.
[28]AddMotion is an animation package embedded within HyperCard, that extends HyperCard's built in animation capabilities.
29See Figure II.23.
[30]See chapter II.5.2, "Unified View Versus Structure-Based Algorithm Animation"
[31] The use of compressed audio file formats such as RealAudio[Rea95] could radically change the design of the audio part, as it allows real-time continuous download. RealAudio is discussed in section IV.6.
[32]The price of a RealAudio server license is about $2,000 to $14,000 (February 1996) depending on the number of concurrently available audio streams.