Driven IFS with Forbidden Combinations

Finite IFSability

From the graph we see there are edges from each vertex to vertex 1, and from each vertex to vertex 4. Consequently, 1 and 4 are the full states. Notice A1 = T1(A) and A4 = T4(A) are copies of A scaled by 1/2.
The only edges leading into vertex 2 come from vertex 1 and from vertex 4. So the only parts of the attractor in the lower right square are A21 = T2(A1) and A24 = T2(A4). These are copies of A scaled by 1/4.
The only edges leading into vertex 3 come from vertex 1, from vertex 2, and from vertex 4. So the only parts of the attractor in the upper left square are A31 = T3(A1), A34 = T3(A4), and A321 = T3(A21) and A324 = T3(A24). The first two are copies of A scaled by 1/4, the last two are copies of A scaled by 1/8.
This is all. One way to see this is to note in the graph every path through a non-rome must enter a rome after passing through only finitely many states. In this case, these paths must be short.
rome → 3 → rome
rome → 2 → 3 → rome
 
To find the rules for the memoryless IFS to generate this fractal, start with the rules for the romes, T1 and T4 in this case, and form all the allowed compositions that do not include another application of a rome rule. These are
T2T1, T2T4, T3T1, T3T4, T3T2T1, and T3T2T4
The corresponding IFS table is
composition r s θ φ e f
T1 0.5 0.5 0 0 0 0
T4 0.5 0.5 0 0 0.5 0.5
T2T1 0.25 0.25 0 0 0.5 0
T2T4 0.25 0.25 0 0 0.75 0.25
T3T1 0.25 0.25 0 0 0 0.5
T3T4 0.25 0.25 0 0 0.25 0.75
T3T2T1 0.125 0.125 0 0 0.25 0.5
T3T2T4 0.125 0.125 0 0 0.375 0.625

Return to representing IFS with memory by IFS without memory.