Rethinking the Objectives of Extractive Question Answering

Understand

This work demonstrates that using the objective with independence assumption for modelling the span probability $P(a_s,a_e) = P(a_s)P(a_e)$ of span starting at position $a_s$ and ending at position $a_e$ has adverse effects.

• Therefore we propose multiple approaches to modelling joint probability $P(a_s,a_e)$ directly.
• Among those, we propose a compound objective, composed from the joint probability while still keeping the objective with independence assumption as an auxiliary objective.
• We find that the compound objective is consistently superior or equal to other assumptions in exact match.