Agent2 = A x Agent 1
Alkali 1 = B - C x Agent 1
Alkali 2 = D - E x Alkali 1
Is there a meaning for the expressions? I think so, and let me explain why I choose these and not others. The first expression shows that there is an optimum relation between two complementary developers. It is known, for instance that Phenidone and Hydroquinone are in a relation close to 1:40, coffee and Vit. C in a relation similar to 1:2 and so on.
Then we know that each developing agent alone needs a certain pH to work well. One is more close to alkali 1 and the other more close to the alkali 2. If agent 1 increases, alkali 1 decreases and alkali 2 increases and vice-versa. In that is why I think that theses expressions serve to describe a family of developers. The developers of the same family must not work the same way, in general they increase activity as the amount of developers rises and maybe you get finer grain and low contrast with those that are less activ than with the others.
This is just a proposal to be analized by you, readers, and I am open for critics or for alternative proposals.
This proposal does not limit the choose and the research of new developers, it seaks for a little more order and choices. Let us assume that you select a certain family of 4 components with A,B,C,D and E of your criterious choice. You may then have several developers with the same ingredients but for different purposes: one is for low speed films, other to get finer grain, other to have more contrast and so on. Just give it a try and see if it works or not.