Component based software engineering
I have a dream...
I have a dream...
Definition
CBSE emphasizes the separation of concerns with respect to the wide-ranging functionality available throughout a given software system. It is a reuse-based approach to defining, implementing and composing loosely coupled independent components into systems.
What is a component?
A piece of software that is connected to other only through its interfaces.
An "interface" is an element that exposes a communication channel with a known contract
Development roles
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System architect (defines the requirements)
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Component designer (implements components)
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System integrator (composes components)
Communication Pattern: request-reply
- A server port provides an interface.
- 0-to-N clients send requests to server.
- The only purpose of the server is to provide answers (replies) as quickly as possible.
- Request can be either synchronous (wait for an answer) or asynchronous (don't wait, poll).
- Server must NOT make any assumption about clients.
Communication Pattern: publish-subscribe
- A publisher exposes data (the topic).
- 0-to-N subscribers notifies that they want to receive the data.
- Publisher must NOT make any assumption about subscribers.
- The interface is always asynchronous for the publisher and might be either SYNC or ASYNC for the subscriber.
Good components have:
- Strongly typed interfaces
- Explicitly documented contracts
- As little state as possible
- A well defined functionality
- An implementation that allow deployment to be configured by the integrator.
ROS doesn't enforce any of this