Parsing xor-based protocol is an extensive operation for resource...

...s and consumes a huge time, or sometimes unterminated

Hello for all;

I still new for Tamarin prover and I counter this problem:
"Parsing xor-based protocol is an extensive operation for resources and consumes a huge time, 
or sometimes unterminated operation"

I've implemented this as follow:

functions:  xor/2, zero/0
equations:  xor(xor(a,b),a)=b,
            xor(xor(a,b),b)=a,
            xor(a,a)=zero,
            xor(zero,a)=a,
            xor(a,zero)=a

Is that correct??