Your definitions seem clear and accurate, but an example of a causal system might help. --Ben Laskowski
Short and to the point. I like the formality of your definitions. The example also helps make sure the reader understands what you're talking about. -Phil Cannon
I like how your definition is short and to the point. However, you may want to note that a non-causal signal may depend on past and present input signals, in addition to future input signals. --Brian Thomas