This document presents Calder, a domain-specific language for visualizing multi-robot systems. Calder is built on top of Mondrian, an interactive information visualization engine. It allows dynamically visualizing and interacting with dynamic graphs representing robot systems. The DSL is embedded in Smalltalk and provides constructs for specifying nodes, edges, layouts, and shapes to build interactive visualizations. Examples demonstrate its use for visualizing multi-robot coverage algorithms. The goal is to make it easier for robotics experts to declaratively specify visualizations that update during simulations.

1. A DSL for the
visualization of Multi-
Robot Systems
Alexandre Bergel (PLEIAD, University of Chile), Serge
Stinckwich (IRD,Vietnam)

2. Problem statement
• Visualization as an aid to design complex
multi-robots algorithms
• Express what need to be visualize in the
context of the domain of the user (robotics
experts here) and in a declarative way
• Adapt the visualization&model during the
simulation (aka. exploratory modeling)

4. Mondrian
• Interactive information visualization engine
• Visualizations can be specified by script
• Embedded Domain-Specific Language
(Smalltalk is the host language)
• Drawback: only static structure

5. From Mondrian to Calder

6. Calder: DSL for
MRS visualization
• Visualize dynamic structures (graphs)
dynamically and interactively
• Interact with individuals nodes and graph as
a whole
• Currently applied to multi-robot systems

7. Smalltalk syntax in a
nutshell
• Everything is an object
• All the computation is done through
objects sending messages to other objects
• 4 types of expressions: literals, variables,
messages and blocks, 11 AST nodes
• Easy to build new DSL + tools to design
your own syntax (Helvetia)

8. Message sending
• Unary message:
view treeLayout
• Binary message:
2+3
• Keywords message:
myArray at: 1 put: 5

9. Blocks
•[3+4]
•[:x | x +1]
•[:x | x +1 ] value: 3 => 4

10. Basic Mondrian
vocabulary
• Nodes
• Edges
• Layout
• Shapes

11. view nodes: classes.
view edges: classes
from: [:each | each superclass]
to: [:each | each].
view treeLayout.

12. view nodes: classes.
view shape rectangle
height:[:each | each
numberOfMethods].
view edges: classes
from:[:each | each superclass]
to:[:each | each].
view treeLayout.

13. Demonstration 1

14. Application: visualization of
MRS coverage algorithms
Nikolaus Corell, Jonathan Bachrach, DanielVickery and Daniela
Rus,“Ad-hoc Wireless Network Coverage with Networked
Robots that Cannot Localize”, ICRA’09, Kobe, Japan

15. Demonstration 2

16. Conclusion&perspectives
• More general than just robotics: can be used to
visualize every dynamic graph of objects
• At the moment, only visualization. Behaviour of
robots can’t be changed very easily.
• Construct a vocabulary suitable to MRS
visualization (motion, perception, ...) in an
iterative way
• Connect to a real robotic simulation engine