So we’ve got a vote here for the ROS interface being the only interface.
I think it is reasonable to have the same information available over different interfaces. Certain tools (e.g. web-based tools) would benefit from not needing to use the DDS stack.
Which interfaces are required, and which interface is considered the “default” interface by tools, are the questions that we need to settle.
How fast a tool using a ROS topic can start up and get the information it wants is something I hope to test today.
I think this overstates the difficulty. If we implement using Python, as an example, there are good libraries available for providing web services, such as Django, CherryPy and several lower-level-but-still-abstracted libraries included in Python 3.
The counter-point there is that, like XML-RPC in ROS1, we would be increasing the number of dependencies if we use something like Django or CherryPi.