You need requirements ... those are characteristics that the target system needs in order to perform its function. The objective spec defines those characteristics. Those must be decomposed into their individual functions, and so on, until every step is absolutely defined, and absolutely essential. No feature should be included, without which the target would function properly, regardless of what someone believes might be "handy" in the next version (extra "features" breed extra "creatures.")

You need research, study, and analysis before design. You have to figure out what to do before you devise how to do it. Coding is nothing but specifying how to do something. They say you shouldn't put the cart before the horse. Isn't that true?

An objective specification is the beginning of the process. When you're finished, you have a design specification that's part of the "documentation" against which you can review your design, even before writing a line of code. That way you can ensure you've "covered all the bases."

RE