Only released in EOL distros:   fuerte

The auction_msgs was created with the objective of defining a more user-friendly mechanism to deal with auction information.

ROS uses a “simplified messages description language for describing the data values (aka messages) that ROS nodes publish. This description makes it easy for ROS tools to automatically generate source code for the message type in several target languages. Message descriptions are stored in .msg files in the msg/ subdirectory of a ROS package”.

For simplicity instead of defining a msg/ folder in each package for the auction protocols, we use a dedicated package for defining the specific Auction and Bid messages. This procedure is a common practice and is advised by the good practices for development in ROS. There are two parts to a .msg file: fields and constants. Fields are the data that is sent inside of the message. Constants define useful values that can be used to interpret those fields (i.e. enum-like constants for an integer value).

The auction messages are defined in the Auction.msg and the Bid.msg files, stored in the msg/ of the auction_msgs package.

Message descriptions are referred to using package resource names. For example, the file auction_msgs/msg/Auction.msg is commonly referred to as auction_msgs/Auction.

To import our auction message types we need to import the auction_msgs module and declare an object that will be of type auction_msgs.msg.Auction or auction_msgs.msg.Bid. The advantages of defining a type of message for both Auction and Bid is evidenced at the development stage when avoiding the definition of numerous variables to define the auction information.

Another advantage is the increased assertiveness while developing the programs since the risk of defining different variable values or omitting others is greatly decreased. The Auction.msg and Bid.msg are defined according to the tables auction_msg and bid_msg.