In a step-wise sequence generation process, let Ψ(Y_i) denote the set of output sequences that are considered complete at step i. Suppose after running the process for three steps, the following sets of complete sequences have been identified:

• Ψ(Y_1) = { "The cat." }
• Ψ(Y_2) = { }
• Ψ(Y_3) = { "It sat.", "A dog." }

Based on the principle that the total search space Y is the aggregation of all complete sequences found across all steps, what is the resulting set Y?

Consider a sequence generation process that runs for a maximum of 5 steps. If a particular sequence is identified as 'complete' at step 2, but the process continues to generate other sequences until step 5, that sequence from step 2 is excluded from the final aggregated search space of all possible complete outputs.

Evaluating a Search Space Construction Method