[ryanmarsh]

The solution to a “complex” problem is only knowable after the fact, versus merely complicated problem which is knowable before the fact. Any sufficiently useful computer program is typically “complex”, though not always.

That said it is still incredibly helpful for everyone to agree on what we’re building in the present iteration/sprint. You mentioned BDD which can be very helpful when paired with a team practice such as Example Mapping[0].

Other practices such as DDD can help you bound the problem and define it. Also there are some helpful lessons in Feature Driven Design.

Source: I teach BDD workshops for a living

[0] https://cucumber.io/blog/2015/12/08/example-mapping-introduc...