Task: Language Identification
Input (Spanish, English): This paper introduces a novel extension of the variational autoencoder to arbitrary tree-structured outputs. Experiments are conducted on a synthetic arithmetic expression dataset and a first-order logic proof clause dataset in order to evaluate its density modeling performance.  Pros: + The paper is clear and well-written. + The tree-structure definition is sufficiently complete to capture a wide variety of tree types found in real-world situations. + The tree generation and encoding procedure is elegant and well-articulated. + The experiments, though limited in scope, are relatively thorough. The use of IWAE to obtain a better estimate of log likelihoods is a particularly nice touch.  Cons: - The performance gain over a baseline sequential model is marginal. - The experiments are limited in scope, both in the datasets considered and in the evaluation metrics used to compare the model with other approaches. Specifically: (a) there is only one set of results on a real-world dataset and in that case the proposed model performs worse than the baseline, and (b) there is no evaluation of the learned latent representation with respect to other tasks such as classification. - The ability of the model to generate trees in time proportional to the depth of the tree is proposed as a benefit of the approach, though this is not empirically validated in the experiments.  The procedures to generate and encode trees are clever in their repeated use of common operations. The weight sharing and gating operations seem important for this model to perform well but it is difficult to assess their utility without an ablation (in Table 1 and 2 these modifications are not evaluated side-by-side). Experiments in another domain (such as modeling source code, or parse trees conditioned on a sentence) would help in demonstrating the utility of this model. Overall the model seems promising and applicable to a variety of data but the lack of breadth in the experiments is a concern.  * Section 3.1: "We distinguish three types" => two * Section 3.6: The exposition of the variable-sized latent state is slightly confusing because the issue of how many z's to generate is not discussed. * Section 4.2-4.3: When generating the datasets, did you verify that the test set is disjoint from the training set? * Table 1: Is there a particular reason why the variable latent results are missing for the depth 11 trees?
Output (English): en