SlowGuess/NAACL_2022_OCR huggingface dataset:
$$
\alpha^ {U} \propto \mathbf {U W} ^ {U}, \mathbf {h} ^ {U} = \alpha^ {U} \mathbf {U},
$$
$$
p _ {c} \propto \operatorname {F F N} \left(\left[ \mathbf {h} ^ {O P}; \mathbf {h} ^ {U}; \mathbf {h} ^ {Q}; \mathbf {h} ^ {P} \right]\right), \tag {13}
$$
Arithmetic Expression Similar to NAQANet (Dua et al., 2019), we perform addition and subtraction over all the numbers mentioned in the context by assigning a sign (plus, minus, or zero) to each number. The probability  $p_{\text{sign}}^i$  of the  $i$ -th number's sign is derived as below:
$$
p _ {s i g n} ^ {i} \propto \mathrm {F F N} ([ \mathbf {h} ^ {O P}; \mathbf {u} ^ {i}; \mathbf {h} ^ {Q}; \mathbf {h} ^ {P} ]). \tag {14}
$$
Multi-Spans Inspired by Segal et al. (2020), the multi-span answer is derived with a sequence role labeling method over the input token sequence, denoted as  $\mathrm{SRL}(\cdot)$ .  $p_{ms}$  is the probability distribution of token's BIO tag:
$$
p _ {m s} = \operatorname {S R L} \left(\left[ \mathbf {H}; \mathbf {h} ^ {O P} \right]\right). \tag {15}
$$