f mapTable ringmap r f is mapped to r where the map is defined by the mapTable, which is generated by makeRingMap as follows: rule ring1 ring2 makeRingMap maptable Example: [(x,y) ring_of_differential_operators ( ) elimination_order 0] define_ring /R1 set [(t,y,z) ring_of_differential_operators ( ) elimination_order 0] define_ring /R2 set [[(x) (Dx)] [((t-1) Dt) (z)]] /r0 set r0 R1 R2 makeRingMap /maptable set (Dx-1) R1 ,, /ff set ff maptable ringmap ::