First, see definitions here.
A "Mandate" is just a visual idiom that a viewer is likely to expect you to use in some situation. Let's suppose it's attractive clouds over a landscape. If you haven't got any clouds over the landscape at the moment, but you really want to make a photograph, you've got a problem, right? This comes under the head of "breaking the rules" in pretty much the same way one might break the "rules" of formal composition. Let me note in passing that your best option may be to pack up for the day, and return when there are some clouds. However, let us move on assuming that's not an option.
Interestingly, music has more or less formalized the process of rule-breaking. I will attempt to translate my poor understanding of those formalisms to the land of photography.
Roughly, what you want to do is prepare the viewer for the broken rule, in music you sneak up on a dissonance by playing chords that are nearby, by almost playing the dissonant chord. When the dissonance arrives, it might be only a single note off of the previous and following chords. Visually, you haven't got time to work with, but you do have space.
The first thing you can do is follow other "rules" more scrupulously, to couch your cloudless sky in a comforting collection of familiar visual tropes: place your main point of visual interest on a "rule of thirds" line, say. The second thing you can do is make it obvious that the rule-breaking is deliberate: do not try to conceal or minimize the cloudless sky. The third thing you can do is wrap the broken rule itself in something familiar and rule-abiding: find a horizon line that's a strong diagonal, or make the sky be a powerful negative space echoing some other shape.
A broken "rule" is a powerful thing, an attention getter, a way to set the viewer ill-at ease and perhaps plant an idea or a feeling, but you mustn't lose the viewer. Give the viewer something comforting and easy to go with your bitter pill.
There is a school of thought which takes the rather silly remark "you have to know the rules in order to break them" and converts that in to "by breaking all the rules at once, I am awesome." A bunch of broken rules is just a mess.