The response time of the system can be broken down into the response time of each stage of the processing pipeline’s longest path. Thus you need to know what the response time patterns of the nodes in that path look like. If we are dealing with a hard real-time system, then it should be possible to define, for a given execution environment, what response time requirement the node is capable of satisfying, which would be useful information for a system integrator. But it seems to me that this is a very specific requirement, as it would be tied completely to your specific environment, including the other nodes and how they execute (e,g, does one of them tend to hog the CPU a little?). So after @iluetkeb’s talk and speaking to him in person, I think that he’s right about the need for tools that make it really easy to understand these sorts of properties of nodes when they are installed in your system, rather than a way to specify something like a maximum update rate capability as part of a node’s interface. That seems like a figure that would change too much between execution environments based on things as obvious as CPU speed and as esoteric as the structure of the disc controller.