What is the convention for topic name parameterization?

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Topic names can be remapped when you start a node, there is no need for a parameter to be explicitly declared in your program. For instance, if my node subscribes to "my_topic" , and you have a node that publishes "your_topic", you could still use my code by remapping the name:

 rosrun my_package my_node my_topic:=your_topic

More information on namespaces and remapping can be found on the wiki: http://www.ros.org/wiki/Remapping%20Arguments

You can also remap topics using launch files using roslaunch's "remap" tag (http://www.ros.org/wiki/roslaunch/XML/remap).