Context-Specific Route Directions

Dissertation project of Kai-Florian Richter

In our research on route directions, we focus on people's conceptualization of routes and the actions necessary to (successfully) follow them. We define conceptualization to be the (process of forming a) mental representation of a route. A route is represented as a sequence of decision point / action pairs. Hence, more precisely, conceptualization is (the process of forming a) mental representation of an (expected) decision point sequence with their accompanying actions. We have developed a process that aims at creating route directions supporting this conceptualization. The generated route directions are easy to process, i.e. they support forming and processing a representation of the corresponding route.

We coin the route directions generated by our model context-specific route directions. We use this term to emphasize that our process explicitly adapts the resulting route directions to the situation at hand, i.e. to the current action to take in the current surrounding environment. This reflects Dey's definition of context: "[...] any information that can be used to characterize the situation of an entity". For this adaptation, we need to account for the characteristics (the structure) of the environment in which route following takes place. The structure of an environment strongly influences the kind of instruction that can be given. The embedding of the route in the spatial structure surrounding it, the structure of that route itself, path annotations, and landmarks that are visible along the route all contribute to this influence. Furthermore, different reference systems provide alternatives to describe necessary actions to follow a route. An analysis of routes and route directions as well as the spatial knowledge required to determine and interpret them results in a systematics of elements that may be used in route directions.

Based on this systematics, we developed and implemented GUARD, a process for the generation of context-specific route directions. GUARD stands for Generation of Unambiguous, Adapted Route Directions. It consists of four steps: in an initial step, every possible description of the action to be performed at each decision point is generated. These descriptions are represented in a relational statement termed abstract turn instruction. The next step combines abstract turn instructions of consecutive decision points into a single instruction, performing so called spatial chunking. As this initial chunking is simply syntax based, in the next step the generated chunks are checked against cognitive and representation-theoretic principles defining valid chunks. Finally, the fourth step generates the route directions in an optimization process. The combination of chunks producing the best route directions is determined. 'Best' here depends on the chosen optimization criterion.

GUARD is flexible with respect to the applied route direction principles. It is possible to combine different principles of chunking with different optimziation criteria, this way testing their appropriateness and performance.

Main publications:

Kai-Florian Richter (2007). A Uniform Handling of Different Landmark Types in Route Directions. In Stephan Winter, Matt Duckham, Lars Kulik, Benjamin Kuipers (Eds.), Stephan Winter, Matt Duckham, Lars Kulik, Benjamin Kuipers Spatial Information Theory. LNCS 4736, pp. 373-389. Springer, Berlin. International Conference COSIT

Kai-Florian Richter, Alexander Klippel (2007). Before or After: Prepositions in Spatially Constrained Systems. Thomas Barkowsky, Markus Knauff, Gérard Ligozat, Daniel R. Montello Spatial Cognition V - Reasoning, Action, Interaction. LNAI 4387, pp. 453-469. Springer, Berlin.

Kai-Florian Richter, Alexander Klippel (2005). A Model for Context-Specific Route Directions. In Christian Freksa, Markus Knauff, Bernd Krieg-Brückner, Bernhard Nebel, Thomas Barkowsky (Eds.), Spatial Cognition IV. Reasoning, Action, Interaction: International Conference Spatial Cognition 2004, pp. 58-78. Springer, Berlin.

Kai-Florian Richter, Alexander Klippel, Christian Freksa (2004). Shortest, Fastest, - but what Next? A Different Approach to Route Directions. In Martin Raubal, Adam Sliwinski, Werner Kuhn (Eds.), Geoinformation und Mobilität - von der Forschung zur praktischen Anwendung. Beiträge zu den Münsteraner GI-Tagen 2004, pp. 205-217, IfGIprints. Institut für Geoinformatik, Münster.