  Recently, the text-to-table generation task has attracted increasing
attention due to its wide applications. In this aspect, the dominant model
formalizes this task as a sequence-to-sequence generation task and serializes
each table into a token sequence during training by concatenating all rows in a
top-down order. However, it suffers from two serious defects: 1) the predefined
order introduces a wrong bias during training, which highly penalizes shifts in
the order between rows; 2) the error propagation problem becomes serious when
the model outputs a long token sequence. In this paper, we first conduct a
preliminary study to demonstrate the generation of most rows is
order-insensitive. Furthermore, we propose a novel sequence-to-sequence&set
text-to-table generation model. Specifically, in addition to a text encoder
encoding the input text, our model is equipped with a table header generator to
first output a table header, i.e., the first row of the table, in the manner of
sequence generation. Then we use a table body generator with learnable row
embeddings and column embeddings to generate a set of table body rows in
parallel. Particularly, to deal with the issue that there is no correspondence
between each generated table body row and target during training, we propose a
target assignment strategy based on the bipartite matching between the first
cells of generated table body rows and targets. Experiment results show that
our model significantly surpasses the baselines, achieving state-of-the-art
performance on commonly-used datasets.
