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Next: ROUTE FINDING ALGORITHM Up: DESIGNING THE ROAD NETWORK Previous: Identification of Classes

Significance of the Model's Components

We consider the classification of the geographic objects into container and non-container features as a semantically significant aspect of our model. While such a classification seems conceptually simple, it plays an important role in route finding problem. Under are the two characteristics of these classes: There are two benefits of this arrangement:
  1. The hierarchy that results corresponds to ``user perspective level''. Thus, a user can have ``country level'' perspective, ``prefecture level'' perspective, etc. Therefore the route finder system, first, will determine the user perspective level and then process according to that level.
  2. One possible query that may be posed in route finder system is: ``Retrieve all the major roads in prefecture X.'' To process such a query, the processor can potentially check each link $l_i$ in road network and use some another algorithm to decide whether it lies in prefecture X or not. This leads to inefficiency of the route finder system. Processing this type of query can be made more efficient, by using a geographic containment hierarchy in our model. Since each container object contains roads entirely contained in it and these contained roads have, also, been divided into different types therefore, the system can find the major roads in prefecture X by just invoking the method GetMajorRoads() defined in prefecture class. Hence there is no need to check each link $l_i$ to be in prefecture X and of type major road. This arrangement greatly reduces the computation time and is more efficient in terms of route finding performance.


next up previous
Next: ROUTE FINDING ALGORITHM Up: DESIGNING THE ROAD NETWORK Previous: Identification of Classes
M.Abaidullah ANWAR
1999-11-25