[h0l0cube]

In terms of something like embedded systems, aerotech, etc., the specification extends all the way to the unit. In terms of an SaaS, the specifications extend all the way to business logic such as (cartoon examples):

- don't charge the customer twice

- or when I click submit on the front-end the following possibilities happen according to the back-end response

- or when the back-end receives x, the inventory should be updated according to this business logic, as well as y

Say if you're doing this capital-A Agile style, all of these should be present on the acceptance criteria for any user story. As someone who's worked in rapid applications development for mobile, I can say reaching this level of specification increases speed, and reduces redundant communication. It often doesn't take half an hour for someone to write, and then it's iterated on by the team before implementation, and during.