Interpreting Motion Expressions in Route Instructions
Using Two Projection-Based Models

UniversitätBremen

Yohei Kurata and Hui Shi
SFB/TR 8 Spatial Cognition, Universität Bremen / {ykurata,shi}@informatik.uni-bremen.deMotivation

Scenario 2: if the landmarks are represented by regions

Mobile robots and intelligent vehicles that navigate in human living
spaces, such as the intelligent wheel chair Rolland[1], should equip with
an ability to communicate with human users about their action plans
through natural language

Model: RfDL3-12

Two types of expressions people may use:
Oriented Expressions
Goal-Oriented• Goale.g., go to the front of …
go behind …
go to the north of …

• Path-Centric Expressions
e.g.,pass … on the leftgo along …
go toward …
go into …

Rolland,Rolland go to thefront of the church
1772 patterns exist• RfDL3-12 is a model that belongs to RfDL model series [3], which consists of eightmodels that categorize the spatial arrangements between a path and a region-likelandmark with different levels of granularities
Rolland, pass thechurch on the left

• The frame adopted by RfDL3-12 is equivalent to that of Double Cross

Correspondence between Motion Expressions and Spatial Patterns:(i) When the route and the landmark are disjoint—the correspondence is sometimes ambiguouse.g., Approach

Research Goal
To model the semantics of path-centric motion expressions
using projection-based spatial models
spatial models that project a frame of spatial reference
onto a space, by which the spatial arrangements ofobjects are distinguishedy ‘approach’
approach
Clearly

May or may not ‘approach’
approach

Clearly not ‘approach’
approach

Strong Condition

In these cases, we cannot tellanything from RfDL3-12 pattern

Weak Conditionat least
one

Thus, we may have to evaluate
the degree of ‘approach’ using
additional criteria

at least
onee.g., Fuzzy Membership Function
If this condition is satisfied,
the motion is always
characterized as ‘approach’Analysisy⎞⎛
1lim ⎜ ∑Δx ⎟⎟− Δ distance( x , R )>αb − a Δx →0⎝⎜ x∈[a,b ] ∧Δx⎠

If this condition is not satisfied,
the motion is nevercharacterized as ‘approach’

In the same way, we determined the strong and weak conditions
for other expressions, such as ‘go away from’ and ‘go by’

Scenario 1: if the landmarks are represented by points
Model: Double Cross [2]μ approach =(ii) When the route intersects with the landmark—topological relations can be used to model the expressions
In this scenario, people typically describe a motion using topological information(i.e., how the route intersects with the landmark). Thus, topological line-region
relations[4] can be used as a basis for capturing typical expressions:

15 patterns exist

go into …

go across …

brush by …

Correspondence between Motion Expressions and Spatial Patterns:— there is a clear correspondence
Approach …

Go to …

Pass / Go by…

Go via …
Leave …

Go away from …

Go toward …
Go until … comesto theh righthPass … on the rightInterestingly, when the landmark is convex, every RfDL3-12 pattern is mapped to aunique topological line-region relations[3]. Moreover, even if the landmark may not
be convex, 77% of RfDL3-12 patterns are mapped to a unique topological relation[3].
This indicates that RfDL3-12 patterns are useful for capturing not only directional,
but also topology-featured motion expressions.

Go straight awayfrom …

…

alwaysgo across …

Ongoing Work
Generalization of the above approach using a spatial ontology [5]Go acrossthe parking
lotPass throughthe car park
gehen Sie überden Parkplaz

References

All the expressions in the left figure refer to the same motion concept.
Thus, once we associate such a concept with RfDL3-12 patterns, wecan support all these expressions simultaneously.
‘Go-Across’ concept…

[1] Lankenau & Röfer (2000) The Role of Shared Control in Service Robots —theBremen Autonomous Wheelchair as an Example. In: Service Robotics—Applications
and Safety Issues in an Emerging Market[2] Freksa (1992) Using Orientation Information for Qualitative Spatial Reasoning. In:International Conference GIS[3] Kurata & Shi (2008) RfDL: Models for Capturing Directional and Topological
Characteristics of Path-Landmark Arrangements. In: Workshop on Moving Object.
[4] Kurata, Y., Egenhofer, M. (2007) The 9+-Intersection for Topological Relations
between a Directed Line Segment and a Region. In: Workshop on Behavioral
Monitoring and Interpretation[5] Shi & Kurata (2008) Modeling Ontological Concepts of Motions with Two ProjectionBased Spatial Models. In: Workshop on Behavioral Monitoring and Interpretation.