What rules or conditions are enforced on signal-flow systems if any?

I read that potential signal-flow systems don't enforce KFL, is KPL enforced or are there just absolutely zero conditions imposed on signal-flow systems and flow and potential have no difference?

I searched around for days and went through the Verilog-ams books but for the life of me can't find the list of conditions that the solver/compiler enforces when only one nature is specified for signal-flow systems.

Many thanks.