I have recently starting using *Mathematica* and have recently come to what seems as an impasse in my understanding of the language. If this is too "tell me how to do it" I would certainly understand.

I have written a program that applies commutator logic to a sequence of creation and annihilation operators to produce a string of Kronecker deltas. I then need to apply the Kronecker delta restrictions to my operators. This is purely symbolic algebra, no real numbers need be produced at the end of the day.

For example, 

 (* KD[a,b] is a Kronecker delta with indices a and b. *)
 (* KD Attributes: Orderless,NumericFunction *)
 (* A[{x},{y}] is an operator with creation indices x and annihilation indices y*)

 In:
 A[{x},{y}] (KD[x,a1]*KD[y,a2]-KD[x,b1]*KD[y,b2])

 Out:
 A[{a1},{a2}]-A[{b1},{b2}]
 
What I have so far:

 In:
 rules=torules[(KD[x,a1]*KD[y,a2]]
 A[{x},{y}]/.rules
 
 Out:
 {x->a1,y->a2}
 A[{a1},{a2}]

This, however, is not quite what I need and converting from KD's to the rules list seems overly complicated. The main issues with this is that I cannot generate operator expressions that have plus within them. The structure of KD is not easily changed, but the input of the operator expressions is quite flexible.