“…Fundamentally, this is because predicting graphs is difficult: every graph has many possible linearizations, so from a probabilistic perspective, the linearization is a latent variable that must be marginalized out (Li et al, 2018). Groschwitz et al (2018) model graphs as trees, interpreted as the (latent) derivation trees of a graph grammar; Lyu and Titov (2018) model graphs with a conditional variant of the classic Erdös and Rényi (1959) model, first predicting an alignment for each node of the output graph, and then predicting, for each pair of nodes, whether there is an edge between them. Buys and Blunsom (2017), Chen et al (2018), and Damonte et al (2017) all model graph generation as a sequence of actions, each aligned to a word in the conditioning sentence.…”