“For the purposes of this discussion, I’m assuming that principles are creative generalisations that form the basis of further reasoning or conduct. Normally, these are expressed as short sentences, and sometimes even single words. Often they are supported by a longer sentence. Generally they come in sets (often between 3 and 7), ideally they are easy to remember (sometimes they are even mnemonic).
Importantly, service design principles are creative, that is they are not like scientific principles which are provable and explanatory, but rather they are intended to provoke further thought and reflection, within a set of creative parameters.”
Nick Marsh of Engine Service Design outlines some of his experiences developing service principles: