URBI

infobox programming language
name = URBI
paradigm = Parallel and Event-driven Interface Language
year = 2003
designer = Jean-Christophe Baillie
developer = Gostai
latest_release_version = 1.0
latest_release_date = April 11 2007
influenced_by = C++, Ruby, Io
operating_system = Cross-platform
license = UObject is GPL, URBI Engine is proprietary

URBI (Universal Real-Time Behavior Interface) is a cross-platform software platform used to develop applications for robotics and artificial intelligence. It is based on the URBI Language which is a parallel and event-driven script language with a C++ like syntax. URBI also integrates a distributed component architecture called UObject, which facilitates the integration of C++ objects in the language as linked or remotely running components.

The URBI Language

URBI has been developed since 2003 by Jean-Christophe Baillie in the Cognitive Robotics Lab of ENSTA, Paris. It is now actively and further developed in the industry through the Gostai company founded in 2006.

URBI as a language can be best described as an interface script language: like LUA in video games, URBI can be used to glue together C++ components into a functional behavior, the CPU-intensive algorithmic part being left to C++ and the behavior scripting part being left to the script language which is more flexible, easy to maintain and allows dynamic interaction during program execution. As an interface language, URBI also brings some useful abstractions to the programmer by having parallelism and event-based programming as part of the language semantics. The scripting of parallel behaviors and reactions to events are core requirements of most robotic and complex AI applications, therfore URBI is well suited to these applications.

Language Attributes

* Parallelism and event-based programming
* Prototype-based programming
* C++ like syntax
* C++ based component architecture (UObject) with possibility to link objects or run them remotely
* Client/Server based architecture
* Client interfaces with Java and Matlab (URBI SDK)
* Cross platform: Linux, Mac, Windows and others. Embeddable, URBI can run on various processors: x86, ARM, mips, powerPC, etc.
* Taggable commands for execution flow control

Cons

* URBI Engine is proprietary (not GPL) and commercial
* Expensive - 990€ for URBI for Webots [http://www.gostai.com/urbi4webots.html]

Examples

The example below shows how to write a ball tracking action/perception loop in URBI: headPan/headTilt are two motor objects, and ball is the ball detection object (x and y range from -1/2 to 1/2):

whenever (ball.visible) { headPan.val = headPan.val + camera.xfov * ball.x & headTilt.val = headTilt.val + camera.yfov * ball.y };

"whenever" is used to trigger a piece of code in loops as long as the associated condition is true. The "&" sign is used to specify that both commands should start at the same time, thus running in parallel.

Other notable event-driven constructs include "at", which triggers the associated code once, at the time when the condition becomes true:

at (speech.hear("hello")) { voice.say("How are you?") & robot.standup(); }

Every command or group of commands is taggable, which provides a way to stop it later if needed:

mytag: while(true) { echo "This is a never ending loop" }, at (button.pressed) stop mytag;

Note in the example above the comma at the end of the command. It will put the preceding command in background, allowing the flow execution to carry on, in particular the next 'at' command to be executed.

UObject component architecture

The UObject component architecture, currently based on the C++ UObject library, allows developers to interface any C++ object within URBI, making selected methods and attributes visible in the script language, while in fact being C++ code. Special notifiers can be set on any of the object's attributes to notify the C++ side of any change on these attributes on the URBI side.

UObject uses C++ templates to transparently map any requested method to an interface machinery that takes care of the type checking.

A C++ UObject can be used in plugged mode if it is directly linked to the URBI Engine at compile time or with dynamic loading. In that case, the C++ object shares the URBI Kernel memory directly, resulting in efficient integration. This is typically used for time critical components like motor or sensor drivers. The same C++ UObject can also be used without modifications as a remote component. In that case, it will become an autonomous program to be executed with the IP address of the URBI Engine as a parameter. In both cases, the object will transparently appear in URBI as a native URBI object.

Components for Robotics: speech, face/object detection, SLAM

Gostai has several plug & play UObject components useful for robotics:

* voice recognition
* voice synthesis
* face detection (including a bridge with Opencv)
* face recognition
* SLAM
* color blob detection
* SIFT based object recognition

Free GPL components developed by the community can be found and exchanged on the urbiforge community website of URBI.

Robotics Simulators compatible with URBI

Webots is the official robot simulator compatible with URBI.

Integration with Player/Stage has been reported, although it is not currently released.

[http://www.anykode.com/ Marilou Robotics Studio] is URBI ready and lets you mount several URBI servers, according to the robot-specific devices.

"URBI-fied" robots & Simulators

Released:
* Webots
* [http://www.anykode.com/ Marilou Robotics Studio]
* Aibo ERS7/ERS2xx
* iRobot Create
* Lego Mindstorms NXT [http://www.gostai.com/nxt]
* HRP2 (restricted release to members of JRL)

Announced:
* Robotis Bioloid
* Surveyor
* Khepera III
* Pioneer
* Aldebaran Nao
* e-puck`

Development environments

URBI comes with URBI Studio that integrates a motion editor for designing dances and animations, and a behavior editor to graphically create finite state machines whose states are simple URBI programs. URBI Studio is cross-platform and generates URBI Code as an output.

ee also

* Robotics suite
* Player Project - probably the most-used robot interface in research and post-secondary education (open source) [http://en.wikipedia.org/wiki/Player_Project]
* RUBIOS - Java based open source communications API for Social Robots. It is designed for academic, hobbyist, and commercial developers and can handle a wide range of robot hardware and software [http://en.wikipedia.org/wiki/RUBIOS]
* Robotic Operating System

External links

* [http://www.gostai.com/technology.html The URBI Technology]
* [http://www.urbiforge.com The URBI Community website]
* [http://www.gostai.com/doc.php URBI Online documentation]
* [http://www.gostai.com/doc/en/urbi-tutorial URBI Tutorial]
* [http://www.gostai.com/doc/en/uobject/ UObject Tutorial]
* [http://www.gostai.com/video.html Videos]