CRC (Classes, Responsibilities, Collaborators)

[mrmanc]

Proposal

Mermaid.js should support CRC cards, as there is no online tool that does so as a first-class citizen that I can find. The same information can be codified as a design represented by a class diagram, but this exercise is a stage before that, with no conversation about inheritance etc.

Use Cases

A CRC exercise is a great step between gathering requirements, and nailing down an OO design using something like a class diagram. It can be done as a stand-alone theoretical design exercise to have good conversations about where responsibility lives, and driving towards a more message orientated design.

Screenshots

See these articles:

• Class Responsibility Collaborator (CRC) Cards: An Agile Introduction
• Class-Responsibility-Collaboration Card

I like to include space for messages in, and messages out, as per this screenshot:

An exercise would generate many of these cards, which could be arranged near their collaborators, with arrows to indicate the relationship between them.

Syntax

crcDiagram
  TrafficLight:
    responsibilities:
      - display current signal
    messagesIn:
      - change signal
    messagesOut:
  Sensor:
    responsibilities:
      - detect vehicle passing
    messagesIn:
    messagesOut:
      - detected vehicle
  Controller:
    responsibilities:
      - coordinate signals
      - balance traffic flow using schedule
      - ensure it is safe to change the traffic flow
    messagesIn:
      - detected vehicle
    messsagesOut:
      - change signal

Implementation

This is a proposal which I'd love to see built into mermaid by the wonderful community.