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Chapter 2. Related Work/Fundamentals 24

The philosophical goals of ROS can be outlined as

• Peer-to-peer topology avoids a central communication server, which will cause unnecessary

traﬃc and can be problematic in heterogeneous networks.

• Tools-based: As ROS is based on an adapted microkernel, it oﬀers a large number of small

tools to run and build ROS components as well as tools to manage complex systems.

• Multi-lingual: Larger projects are usually developed by several people, who often use their

own programming languages. In order to facilitate this cooperation and reach a wider

audience, ROS nodes can be programmed in multiple programming languages. (C++,

Python, LISP and Java)

• Thin: Code could be reusable in many cases, but it is often wrapped up in middleware,

which makes it hard to extract it. ROS, therefore, performs modular builds in the source

code tree to keep dependencies low and facilitate the reuse of code.

• Free and Open-Source: ROS is released under the BSD license making it free for private

and commercial use. This encourages many people to use it, resulting in a broad community

and a number of available packages for ﬁelds of applications.

ROS is primarily designed for robotic applications and is not specialised for use in Home Automa-

tion or Intelligent Environments. However, both HA and IE can be described as ImmoBots [27],

which are robots with typical characteristics of a robot, such as sensor richness and autonomy, but

are not mobile. Roalter et al. describe in [16], how ROS can be used in Intelligent Environments.

Technical aspects

ROS consists of diﬀerent main components: nodes, messages, topics, services and the ROS master.

Nodes are small software modules that perform computation. They can represent processing

algorithms and diﬀerent functions, such as drivers for sensors and actuators. A system usually

consists of many nodes, which communicate over topics and services. This ﬁne subdivision makes

ROS programs very modular and easy to manage.

Topics are used to exchange data between diﬀerent nodes. A node sends data by publishing

it on a certain topic to which all interested nodes can subscribe and receive the data. Every

topic can have multiple publishers/subscribers and every node can publish/subscribe to multiple

topics. This asynchronous data transmission abstracts the transmitter and receiver side, therefore

publisher and subscriber are not aware of each other. Topics consist of a name and a message

type.

http://www.generationrobots.com/ros-robot-operating-system,us,8,74.cfm

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