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Chapter 1
Introduction

Urbi SDK is a fully-featured environment to orchestrate complex organizations of components. It relies on a middleware architecture that coordinates components named UObjects. It also features urbiscript, a scripting language that can be used to write orchestration programs.

 1.1 Urbi and UObjects
 1.2 Urbi and urbiscript
 1.3 Genesis
 1.4 Outline

1.1 Urbi and UObjects

Urbi makes the orchestration of independent, concurrent, components easier. It was first designed for robotics: it provides all the needed features to coordinate the execution of various components (actuators, sensors, software devices that provide features such as text-to-speech, face recognition and so forth). Languages such as C ++ are well suited to program the local, low-level, handling of these hardware or software devices; indeed one needs efficiency, small memory footprint, and access to low-level hardware details. Yet, when it comes to component orchestration and coordination, in a word, when it comes to addressing concurrency, it can be tedious to use such languages.

Middleware infrastructures make possible to use remote components as if they were local, to allow concurrent execution, to make synchronous or asynchronous requests and so forth. The UObject C ++ architecture provides exactly this: a common API that allows conforming components to be used seamlessly in highly concurrent settings. Components need not be designed with UObjects in mind, rather, UObjects are typically “shells” around “regular” components.

Components with an UObject interface are naturally supported by the urbiscript programming language. This provides a tremendous help: one can interact with these components (making queries, changing them, observing their state, monitoring various kinds of events and so forth), which provides a huge speed-up during development.

Finally, note that, although made with robots in mind, the UObject architecture is well suited to tame any heavily concurrent environment, such as video games or complex systems in general.

1.2 Urbi and urbiscript

urbiscript is a programming language primarily designed for robotics. It’s a dynamic, prototype-based, object-oriented scripting language. It supports and emphasizes parallel and event-based programming, which are very popular paradigms in robotics, by providing core primitives and language constructs.

Its main features are:

1.3 Genesis

Urbi what first designed and implemented by Jean-Christophe Baillie, together with Matthieu Nottale. Because its users wildly acclaimed it, Jean-Christophe founded Gostai, a France-based Company that develops software for robotics with a strong emphasis on personal robotics.

Authors Urbi SDK 1 was further developed by Akim Demaille, Guillaume Deslandes, Quentin Hocquet, and Benot Sigoure.

The Urbi SDK 2 project was started and developed by Akim Demaille, Quentin Hocquet, Matthieu Nottale, and Benot Sigoure. Samuel Tardieu provided an immense help during the year 2008, in particular for the concurrency and event support.

The maintenance is currently carried out by Akim Demaille, Quentin Hocquet, and Matthieu Nottale. Jean-Christophe Baillie is still deeply involved in the development of urbiscript, he regularly submits ideas, and occasionally even code!

Contributors A number of people contributed significantly to Urbi, including Romain Bezut, Thomas Moulard, Nicolas Pierron.

1.4 Outline

This multi-part document provides a complete guide to Urbi. See paragraph 30 for the various notations that are used in the document.

Listing I Urbi and UObjects User Manual
 
This part covers the Urbi architecture: its core components (client/server architecture), how its middleware works, how to include extensions as UObjects (C ++ components) and so forth.

No knowledge of the urbiscript language is needed. As a matter of fact, Urbi can be used as a standalone middleware architecture to orchestrate the execution of existing components.

Yet urbiscript is a feature that “comes for free”: it is easy using it to experiment, prototype, and even program fully-featured applications that orchestrate native components. The interested reader should read either the urbiscript user manual (Listing II), or the reference manual (Section 19).

  Listing 3 The UObject API
 
This section shows the various steps of writing an Urbi C ++ component using the UObject API.
  Listing 4 Use Cases
 
Interfacing a servomotor device as an example on how to use the UObject architecture as a middleware.
Listing II urbiscript User Manual  
This part, also known as the “urbiscript tutorial”, teaches the reader how to program in urbiscript. It goes from the basis to concurrent and event-based programming. No specific knowledge is expected. There is no need for a C ++ compiler, as UObject will not be covered here (see Listing I). The reference manual contains a terse and complete definition of the Urbi environment (Section IV).
  Listing 5 First Steps
 
First contacts with urbiscript.
  Section 6 Basic Objects, Value Model
 
A quick introduction to objects and values.
  Section 7 Flow Control Constructs
 
Basic control flow: if, for and the like.
  Listing 8 Advanced Functions and Scoping
 
Details about functions, scoped, and lexical closures.
  Listing 9 Objective Programming, urbiscript Object Model
 
A more in-depth introduction to object-oriented programming in urbiscript.
  Listing 10 Functional Programming
 
Functions are first-class citizens.
  Listing 11 Parallelism, Concurrent Flow Control
 
The urbiscript operators for concurrency, tags.
  Listing 12 Event-based Programming
 
Support for event-driven concurrency in urbiscript.
  Listing 13 Urbi for ROS Users
 
How to use ROS from Urbi, and vice-versa.
Listing III Guidelines and Cook Books  
This part contains guides to some specific aspects of Urbi SDK.
  Listing 14 Installation
 
Complete instructions on how to install Urbi SDK.
  Section 15 Frequently Asked Questions
 
Some answers to common questions.
  Section 16 Migration from urbiscript 1 to urbiscript 2
 
This chapter is intended to people who want to migrate programs in urbiscript 1 to urbiscript 2.
  Listing 17 Building Urbi SDK
 
Building Urbi SDK from the sources. How to install it, how to check it and so forth.
Section IV Urbi SDK Reference Manual  
This part defines the specifications of the urbiscript language version 2.0. It defines the expected behavior from the urbiscript interpreter, the standard library, and the SDK. It can be used to check whether some code is valid, or browse urbiscript or C ++ API for a desired feature. Random reading can also provide you with advanced knowledge or subtleties about some urbiscript aspects.

This part is not an urbiscript tutorial; it is not structured in a progressive manner and is too detailed. Think of it as a dictionary: one does not learn a foreign language by reading a dictionary. The urbiscript Tutorial (Listing II), or the live urbiscript tutorial built in the interpreter are good introductions to urbiscript.

This part does not aim at giving advanced programming techniques. Its only goal is to define the language and its libraries.

  Section 18 Programs
 
Presentation and usage of the different tools available with the Urbi framework related to urbiscript, such as the Urbi server, the command line client, umake, …
  Section 19 urbiscript Language Reference Manual
 
Core constructs of the language and their behavior.
  Listing 20 urbiscript Standard Library
 
Listing of all classes and methods provided in the standard library.
  Section 21 Communication with ROS
 
Urbi provides a set of tools to communicate with ROS (Robot Operating System). For more information about ROS, see http://www.ros.org. Urbi, acting as a ROS node, is able to interact with the ROS world.
  Section 22 Gostai Standard Robotics API
 
Also known as “The Urbi Naming Standard”: naming conventions in for standard hardware/software devices and components implemented as UObject and the corresponding slots/events to access them.
Listing V Urbi Platforms  
This part covers the specific features of Urbi for some of the platforms it was ported to. Environments not described in this part are covered in separate, stand-alone, documentations.
  Listing 23 Bioloid
 
Using the Bioloid robot construction kit with Urbi.
  Listing 24 Mindstorms NXT
 
LEGO Mindstorms NXT is a programmable robotics kit released by Lego in July 2006, replacing the first-generation LEGO Mindstorms kit. The kit consists of 519 Technic pieces, 3 servo motors, 4 sensors (ultrasonic, sound, touch, and light), 7 connection cables, a USB interface cable, and the NXT Intelligent Brick.
  Section 25 Nao
 
Programming Aldebaran’s Nao using Urbi.
  Listing 26 Pioneer 3-DX
 
Pioneer 3-DX8 is an agile, versatile intelligent mobile robotic platform updated to carry loads more robustly and to traverse sills more surely with high-performance current management to provide power when it’s needed.
  Section 27 Segway RMP
 
The Segway Robotic Mobility Platform is a robotic platform based on the Segway Personal Transporter.
  Section 28 Spykee
 
The Spykee is a WiFi-enabled robot built by Meccano (known as Erector in the United States). It is equipped with a camera, speaker, microphone, and moves using two tracks.
  Listing 29 Webots
 
Using Cyberbotics’ Webots simulation environment with Urbi.
paragraph VI Tables and Indexes  
This part contains material about the document itself.
  paragraph 30 Notations
 
Conventions used in the type-setting of this document.
  Section 32 Licenses
 
Licenses of components used in Urbi SDK.
  Listing 31 Release Notes
 
Release notes of Urbi SDK.
  Section 33 Glossary
 
Definition of the terms used in this document.