Abstract 1 1 Introduction 2
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- 3.1Navigation in Physical Space
3NavigationAccording to the Oxford English Dictionary, Navigation is “2. a. The art or science of directing the movements of ships on the sea, including more especially the methods of determining a ship's position and course by the principles of geometry and nautical astronomy; seamanship.” Reasonable parallels exist in our use of the term navigation. Navigation is “the art or science of directing our movements through a document space, including methods for determining where we are and how we get some place by principles of …” What the principles are that correspond to astronomy, seamanship, and geometry is the focus of this section. With the size of document spaces increasing, navigation becomes more difficult. Navigational tools are increasingly important in such spaces. The previous section discussed types of document spaces, including hypertext spaces. Conklin (1987, p.57) uses the phrase “Lost in Space” to describe the disorientation problem associated with hypertext systems. This phrase has been restated in a variety of forms including “being lost in hyperspace” (Nielsen, 1990, p.127). While this paper addresses navigation in document spaces, the more general problem is navigation in an “information space,” which would include not only navigation in hypertexts, document sets, and file spaces, but navigation in DBMSs and other kinds of data spaces as well. There are varieties of solutions to disorientation in a document space -- organization of the space, limitation of the space, robot retrieval tools over the space, etc. In this section, a detail of navigation will be investigated. Navigation and navigation tools in document spaces will be examined. Navigation in document space will be compared and contrasted to navigation in physical space. Problems that are specific to document space navigation will be explored. Finally, a classification of navigation tools will be proposed. The basic aspects of navigation are presented by Jul and Furnas (1997). They indicate that navigation is a process that makes use of the ability of a body to move, i.e. locomotion, and to make decisions about where to move. Locomotion assumes the concepts of location and direction. The decisions that are made sometimes follow a plan and sometimes respond to the environment according to some goal. They depend on both declarative and procedural knowledge and frequently require coordination of knowledge in different forms (orientation). Thus, navigation is an incremental real-time process that integrates these two components (locomotion and decision-making). Finally, a mental or physical map of space is built. Jul and Furnas also reported a discussion of situated navigation, in contrast to plan-based navigation, models of navigation, and other issues including characteristics of the space, task, strategy, and user knowledge. Other frameworks in navigation can be found in Spence (1998). Spence divides navigation activity into browsing, context modeling, gradient perception and strategy formulation. These activities are driven by intention. 3.1Navigation in Physical SpaceNavigation is a process that plans a way through space. In general, navigation is considered to have the following sub-processes:
The planned path may be chosen from previous data about the conditions of the paths. While going through the path, the choice of path may be re-evaluated based upon current conditions, and a new path then selected. If the path is trivial, going to a destination may not be regarded as navigation, e.g. walking across a field. Navigation requires an intermediate step between a current position and destination, and it should have alternative paths which may not lead to the destination. Navigation also requires a decision among paths. Jul and Furnas use a different taxonomy of navigation subtasks. They identify navigation tasks of locomotion, steering, traversal, route following, route finding, and map building as the relevant types. In contrast to navigation, exploration is another mode of moving in space. The difference would seem to be that while exploration may have a specific destination, the location of the destination may not be known. Exploration covers a lot of space and learns about space. Exploration needs some form of navigation to avoid getting lost in space. It also needs a trail to distinguish places that have been visited from places that have not. One may consider exploration as one mode of navigation (Whitaker, 1997). The navigational process relies on knowledge about space. Knowledge about physical space primarily comes from the senses, either directly, from the environment, or indirectly, through a map or some other representational aid. There are differences between small physical spaces those within the line of sight, and large spaces. Both route and survey perspectives are commonly used to communicate spatial knowledge. A route perspective may use observers as a frame of reference, i.e. an egocentric perspective. Alternatively the environment can be described by a relative direction of a landmark to an observer. A survey perspective takes a view from above, an exocentric frame of reference, and describes environments relative to one another. On a small scale, such as a tabletop view, or on a very large scale, such as a state level or globe level, we get spatial knowledge from survey perspectives. We look from above onto a table or map, because either we cannot be within the environment or the environment is too large to obtain route information. Tversky, Franklin, Taylor, and Bryant (1994) indicated that the perspectives information, either route or survey, is not encoded in spatial mental models. Knowledge of route and survey perspectives can be transformed to each other equally well. However, our “cognitive map” is not as accurate as the physical map. Hirtle and Jonides (1985) reported on evidence of hierarchical relations in recognition of places. In our knowledge about physical space, some objects are considered landmarks. Landmarks are special objects and are different from other objects in that environment. Landmarks are used as points of reference in a space. Download 324.2 Kb. Share with your friends:
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