x1=j1=pu1=pi1=pi3 is the result / output of application of [function]/[selbri] x2=j2=pu2=pi2 to [input]/[sumti]/[application]/[termset] x3=pu3.
For agentive application / applying, consider using gau or adding a suffix of gau to prepend an x1 agent place. ni'o Contraction: pli'aje.