added publications from 2019 to Simplification (#413)

* added new task simplification

* added new task simplification

* added publications from 2019

* added publications from 2019

english/simplification.md

@@ -25,16 +25,18 @@ When the set of transformations is limited to replacing a word or phrase by a si
 
 ### Evaluation
 
-The ideal method for determining the quality of a simplification is through human evaluation. Traditionally, a simplified output is judged in terms of *grammaticality* (or fluency), *meaning preservation* (or adequacy) and *simplicity*, using Likert scales (1-3 or 1-5) . **Warning:** Are these criteria (at the sentence level) the most appropriate for assessing a simplified sentence? It has been suggested [(Siddharthan, 2014)](https://www.jbe-platform.com/content/journals/10.1075/itl.165.2.06sid) that a task-oriented evaluation (e.g., through reading comprehension tests [(Angrosh et al., 2014)](http://aclweb.org/anthology/C14-1188)) could be more informative of the usefulness of the generated simplification. However, this is not general practice.
+The ideal method for determining the quality of a simplification is through human evaluation. Traditionally, a simplified output is judged in terms of *grammaticality* (or fluency), *meaning preservation* (or adequacy) and *simplicity*, using Likert scales (1-3 or 1-5) . **Warning:** Are these criteria (at the sentence level) the most appropriate for assessing a simplified sentence? It has been suggested [(Siddharthan, 2014)](https://www.jbe-platform.com/content/journals/10.1075/itl.165.2.06sid) that a task-oriented evaluation (e.g. through reading comprehension tests [(Angrosh et al., 2014)](http://aclweb.org/anthology/C14-1188)) could be more informative of the usefulness of the generated simplification. However, this is not general practice.
 
-For tuning and comparing models, the most commonly used automatic metrics are:
+For tuning and comparing models, the most commonly-used automatic metrics are:
 
-- **BLEU** [(Papineni et al., 2012)](https://aclweb.org/anthology/P02-1040), borrowed from Machine Translation. This metric is not one without [problems](https://towardsdatascience.com/evaluating-text-output-in-nlp-bleu-at-your-own-risk-e8609665a213) for different text generation tasks. However, simplification studies ([Stajner et al., 2014](http://aclweb.org/anthology/W14-1201); [Wubben et al., 2012](http://aclweb.org/anthology/P12-1107); [Xu et al., 2016](http://aclweb.org/anthology/Q16-1029)) have shown that it correlates with human judgments of grammaticality and meaning preservation. BLEU is not well suited, though, for assessing simplicity from a lexical [(Xu et al., 2016)](http://aclweb.org/anthology/Q16-1029) nor a structural [(Sulem et al., 2018b)](http://aclweb.org/anthology/D18-1081) point of view .
+- **BLEU** [(Papineni et al., 2012)](https://aclweb.org/anthology/P02-1040), borrowed from Machine Translation. This metric is not one without [problems](https://towardsdatascience.com/evaluating-text-output-in-nlp-bleu-at-your-own-risk-e8609665a213) for different text generation tasks. However, simplification studies ([Stajner et al., 2014](http://aclweb.org/anthology/W14-1201); [Wubben et al., 2012](http://aclweb.org/anthology/P12-1107); [Xu et al., 2016](http://aclweb.org/anthology/Q16-1029)) have shown that it correlates with human judgments of grammaticality and meaning preservation. BLEU is not well suited, though, for assessing simplicity from a lexical [(Xu et al., 2016)](http://aclweb.org/anthology/Q16-1029) nor a structural [(Sulem et al., 2018b)](http://aclweb.org/anthology/D18-1081) point of view.
 - **SARI** [(Xu et al., 2016)](http://aclweb.org/anthology/Q16-1029) is a *lexical simplicity* metric that measures "how good" are the words added, deleted and kept by a simplification model. The metric compares the model's output to *multiple simplification references* and the original sentence. SARI has shown high correlation with human judgements of simplicity gain [(Xu et al., 2016)](http://aclweb.org/anthology/Q16-1029). Currently, this is the main metric used for evaluating sentence simplification models.
 
 The previous two metrics will be used to rank the models in the following sections. Despite popular practice, we refrain from using **Flesch Reading Ease** or **Flesch-Kincaid Grade Level**. Because of the way these metrics are [computed](https://en.wikipedia.org/wiki/Flesch%E2%80%93Kincaid_readability_tests), short sentences could get good scores, even if they are ungrammatical or non-meaning preserving [(Wubben et al., 2012)](http://aclweb.org/anthology/P12-1107), resulting in a missleading ranking. 
 
-Finally, as seen in the previous section, a simplification could involve text transformations beyond paraphrasing (which SARI intends to assess).  For these cases, it could be more suitable to use **SAMSA** [(Sulem et al., 2018a)](http://aclweb.org/anthology/N18-1063), a recently introduced metric for measuring *structural simplicity* (i.e., sentence splitting). However, it has not been used in papers besides the one where it was introduced (yet).
+Since a simplification could involve text transformations beyond paraphrasing (which SARI intends to assess).  For these cases, it could be more suitable to use **SAMSA** [(Sulem et al., 2018a)](http://aclweb.org/anthology/N18-1063), a metric designed to measure *structural simplicity* (i.e. sentence splitting). However, it has not been used in papers besides the one where it was introduced (yet).
+
+**EASSE:** [Alva-Manchego et al. (2019)](https://www.aclweb.org/anthology/D19-3009) released a [tool](https://github.com/feralvam/easse) that provides easy access to all of the above metrics (and several others) through the command line and as a python package. EASSE also contains commonly-used test sets for the task. Its aim is to help standarise automatic evaluation for sentence simplification.
 
 **IMPORTANT NOTE:** In the tables of the following sections, a score with a \* means that it was not reported by the original authors but by future research that re-implemented and/or re-trained and re-tested the model. In these cases, the original reported score (if there is one) is shown in parentheses. 
 
@@ -46,10 +48,12 @@ Finally, as seen in the previous section, a simplification could involve text tr
 
 [Zu et al. (2010)](http://aclweb.org/anthology/C10-1152) compiled a parallel corpus with more than 108K sentence pairs from 65,133 Wikipedia articles, allowing **1-to-1 and 1-to-N alignments**. The latter type of alignments represents instances of sentence splitting. The original full corpus can be found [here](https://www.informatik.tu-darmstadt.de/ukp/research_6/data/sentence_simplification/simple_complex_sentence_pairs/index.en.jsp). The test set is composed of 100 instances, with **one simplification reference per original sentence**. [Zhang and Lapata (2017)](http://aclweb.org/anthology/D17-1062) released a more standardised split of this dataset called [*WikiSmall*](https://github.com/XingxingZhang/dress), with 89,042 instances for training, 205 for development and the same original 100 instances for testing. 
 
-We present the models tested in this dataset **ranked by BLEU score**. SARI cannot be reliably computed in this dataset since it does not contain multiple simplification references per original sentence. In addition, there are instances of more advanced simplification transformations (e.g., splitting) which SARI does not assess by definition.
+We present the models tested in this dataset **ranked by BLEU score** (or SARI if BLEU is not available). SARI cannot be reliably computed in this dataset since it does not contain multiple simplification references per original sentence. In addition, there are instances of more advanced simplification transformations (e.g. splitting) which SARI does not assess by definition.
 
 | Model           | BLEU | SARI | Paper / Source | Code |
 | --------------- | :-----: | :-----: | -------------- | ---- |
+| EditNTS (Dong et al., 2019) |  | 32.35 | [EditNTS: An Neural Programmer-Interpreter Model for Sentence Simplification through Explicit Editing](https://www.aclweb.org/anthology/P19-1331) | [Official](https://github.com/yuedongP/EditNTS) |
+| SeqLabel (Alva-Manchego et al., 2017) |  | 30.50\* | [Learning How to Simplify From Explicit Labeling of Complex-Simplified Text Pairs](https://www.aclweb.org/anthology/I17-1030) | |
 | Hybrid (Narayan and Gardent, 2014) | 53.94\* (53.6) | 30.46\* | [Hybrid Simplification using Deep Semantics and Machine Translation](http://aclweb.org/anthology/P/P14/P14-1041.pdf) | [Official](https://github.com/shashiongithub/Sentence-Simplification-ACL14) |
 | NSELSTM-B (Vu et al., 2018) | 53.42 | 17.47 | [Sentence Simplification with Memory-Augmented Neural Networks](http://aclweb.org/anthology/N18-2013) |  |
 | PBMT-R (Wubben et al., 2012) | 46.31\* (43.0) | 15.97\* | [Sentence Simplification by Monolingual Machine Translation](http://aclweb.org/anthology/P12-1107) |  |
@@ -74,21 +78,25 @@ We present the models tested in this dataset **ranked by BLEU score**. SARI cann
 
 #### Turk Corpus
 
-Together with defining SARI, [Xu et al. (2016)](http://aclweb.org/anthology/Q16-1029) released a dataset properly collected to calculate the simplicity metric: **1-to-1 alignments** focused on paraphrasing transformations (extracted from PWKP), and **multiple (8) simplification references per original sentence** (collected through Amazon Mechanical Turk). The  [dataset](https://github.com/cocoxu/simplification/) contains 2,350 sentences split into 2,000 instances for tuning and 350 for testing. For training, most models use [*WikiLarge*](https://github.com/XingxingZhang/dress), which was compiled by [Zhang and Lapata (2017)](http://aclweb.org/anthology/D17-1062) using alignments from other Wikipedia-based datasets ([Zhu et al., 2010](http://aclweb.org/anthology/C10-1152); [Woodsend and Lapata, 2011](http://aclweb.org/anthology/D11-1038); [Kauchak, 2013](http://aclweb.org/anthology/P13-1151)), and contains 296K instances of not only 1-to-1 alignments. 
+Together with defining SARI, [Xu et al. (2016)](http://aclweb.org/anthology/Q16-1029) released a dataset properly collected to calculate this simplicity metric: **1-to-1 alignments** focused on paraphrasing transformations (extracted from PWKP), and **multiple (8) simplification references per original sentence** (collected through Amazon Mechanical Turk). The  [dataset](https://github.com/cocoxu/simplification/) contains 2,350 sentences split into 2,000 instances for tuning and 350 for testing. For training, most models use [*WikiLarge*](https://github.com/XingxingZhang/dress), which was compiled by [Zhang and Lapata (2017)](http://aclweb.org/anthology/D17-1062) using alignments from other Wikipedia-based datasets ([Zhu et al., 2010](http://aclweb.org/anthology/C10-1152); [Woodsend and Lapata, 2011](http://aclweb.org/anthology/D11-1038); [Kauchak, 2013](http://aclweb.org/anthology/P13-1151)), and contains 296K instances of not only 1-to-1 alignments. 
 
 We present the models tested in this dataset **ranked by SARI score**.
 
 | Model           | BLEU | SARI | Paper / Source | Code |
 | --------------- | :-----: | :-----: | -------------- | ---- |
+| ACCESS (Martin et al., 2019) |  | 41.87  | [Controllable Sentence Simplification](https://arxiv.org/abs/1910.02677) | [Official](https://github.com/facebookresearch/access) |
 | DMASS + DCSS (Zhao et al., 2018) |  | 40.45 | [Integrating Transformer and Paraphrase Rules for Sentence Simplification](http://aclweb.org/anthology/D18-1355) | [Official](https://github.com/Sanqiang/text_simplification) |
 | SBSMT + PPDB + SARI (Xu et al, 2016) | 73.08\* (72.36) | 39.96\* (37.91) | [Optimizing Statistical Machine Translation for Text Simplification](http://aclweb.org/anthology/Q16-1029) | [Official](https://github.com/cocoxu/simplification/) |
 | PBMT-R (Wubben et al., 2012) | 81.11\* | 38.56\* | [Sentence Simplification by Monolingual Machine Translation](http://aclweb.org/anthology/P12-1107) |  |
+| EditNTS (Dong et al., 2019) |  | 38.22 | [EditNTS: An Neural Programmer-Interpreter Model for Sentence Simplification through Explicit Editing](https://www.aclweb.org/anthology/P19-1331) | [Official](https://github.com/yuedongP/EditNTS) |
 | Pointer + Multi-task Entailment and Paraphrase Generation (Guo et al., 2018) | 81.49 | 37.45 | [Dynamic Multi-Level Multi-Task Learning for Sentence Simplification](http://aclweb.org/anthology/C18-1039) | [Official](https://github.com/HanGuo97/MultitaskSimplification) |
 | NTS + SARI (Nisioi et al., 2017) | 80.69 | 37.25 | [Exploring Neural Text Simplification Models](http://aclweb.org/anthology/P17-2014) | [Official](https://github.com/senisioi/NeuralTextSimplification) |
 | DRESS-LS (Zhang and Lapata, 2017) | 80.12 | 37.27 | [Sentence Simplification with Deep Reinforcement Learning](http://aclweb.org/anthology/D17-1062) | [Official](https://github.com/XingxingZhang/dress) |
 | DRESS (Zhang and Lapata, 2017) | 77.18 | 37.08 | [Sentence Simplification with Deep Reinforcement Learning](http://aclweb.org/anthology/D17-1062) | [Official](https://github.com/XingxingZhang/dress) |
+| SeqLabel (Alva-Manchego et al., 2017) |  | 37.08\* | [Learning How to Simplify From Explicit Labeling of Complex-Simplified Text Pairs](https://www.aclweb.org/anthology/I17-1030) | |
 | NSELSTM-S (Vu et al., 2018) | 80.43 | 36.88 | [Sentence Simplification with Memory-Augmented Neural Networks](http://aclweb.org/anthology/N18-2013) |  |
 | SEMoses (Sulem et al., 2018)                                 |      74.49       |     36.70      | [Simple and Effective Text Simplification Using Semantic and Neural Methods](http://aclweb.org/anthology/P18-1016) | [Official](https://github.com/eliorsulem/simplification-acl2018) |
+| UnsupNTS (Surya et al., 2019) | 76.13 | 35.29 | [Unsupervised Neural Text Simplification](https://www.aclweb.org/anthology/P19-1198) | [Official](https://github.com/subramanyamdvss/UnsupNTS) |
 | NSELSTM-B (Vu et al., 2018) | 92.02 | 33.43 | [Sentence Simplification with Memory-Augmented Neural Networks](http://aclweb.org/anthology/N18-2013) | |
 | Hybrid (Narayan and Gardent, 2014) | 48.97\* | 31.40\* | [Hybrid Simplification using Deep Semantics and Machine Translation](http://aclweb.org/anthology/P/P14/P14-1041.pdf) | [Official](https://github.com/shashiongithub/Sentence-Simplification-ACL14) |
 
@@ -110,9 +118,12 @@ Using their splits, [Zhang and Lapata (2017)](http://aclweb.org/anthology/D17-10
 
 | Model           | BLEU | SARI | Paper / Source | Code |
 | --------------- | :-----: | :-----: | -------------- | ---- |
+|S2S-Cluster-FA (Kriz et al., 2019) |  | 37.22 | [Complexity-Weighted Loss and Diverse Reranking for Sentence Simplification](https://www.aclweb.org/anthology/N19-1317) | [Official](https://github.com/rekriz11/sockeye-recipes) |
 | Pointer + Multi-task Entailment and Paraphrase Generation (Guo et al., 2018) | 11.14 | 33.22 | [Dynamic Multi-Level Multi-Task Learning for Sentence Simplification](http://aclweb.org/anthology/C18-1039) | [Official](https://github.com/HanGuo97/MultitaskSimplification) |
+| EditNTS (Dong et al., 2019) |  | 31.41 | [EditNTS: An Neural Programmer-Interpreter Model for Sentence Simplification through Explicit Editing](https://www.aclweb.org/anthology/P19-1331) | [Official](https://github.com/yuedongP/EditNTS) |
 | Hybrid (Narayan and Gardent, 2014) | 14.46\* | 30.00\* | [Hybrid Simplification using Deep Semantics and Machine Translation](http://aclweb.org/anthology/P/P14/P14-1041.pdf) | [Official](https://github.com/shashiongithub/Sentence-Simplification-ACL14) |
 | NSELSTM-S (Vu et al., 2018) | 22.62 | 29.58 | [Sentence Simplification with Memory-Augmented Neural Networks](http://aclweb.org/anthology/N18-2013) | |
+| SeqLabel (Alva-Manchego et al., 2017) |  | 29.53\* | [Learning How to Simplify From Explicit Labeling of Complex-Simplified Text Pairs](https://www.aclweb.org/anthology/I17-1030) | |
 | NSELSTM-B (Vu et al., 2018) | 26.31 | 27.42 | [Sentence Simplification with Memory-Augmented Neural Networks](http://aclweb.org/anthology/N18-2013) | |
 | DRESS (Zhang and Lapata, 2017) | 23.21 | 27.37 | [Sentence Simplification with Deep Reinforcement Learning](http://aclweb.org/anthology/D17-1062) | [Official](https://github.com/XingxingZhang/dress) |
 | DMASS + DCSS (Zhao et al., 2018) |  | 27.28 | [Integrating Transformer and Paraphrase Rules for Sentence Simplification](http://aclweb.org/anthology/D18-1355) | [Official](https://github.com/Sanqiang/text_simplification) |
@@ -122,8 +133,8 @@ Using their splits, [Zhang and Lapata (2017)](http://aclweb.org/anthology/D17-10
 As mentioned before, a big disadvantage of the Newsela corpus is that a unique train/dev/test split of the data is not (cannot be made?) publicly available. In addition, due to its characteristics, it is not clear what should be the best way to generate sentence alignments and split the data:
 
 -  [Zhang and Lapata (2017)](http://aclweb.org/anthology/D17-1062) removed sentences from version pairs 0–1, 1–2, and 2–3 because they are "too similar to each other". This could prevent the model from learning when a sentence should not be simplified. In addition, their test set only considers 1-to-1 sentence alignments, even though it is possible to generate 1-to-N and N-to-1 sentence pairs as shown by other researchers ([Scarton et al., 2018](http://aclweb.org/anthology/L18-1553); [Stajner et al., 2018](http://aclweb.org/anthology/L18-1615)).
-- [Alva-Manchego et al. (2017)](http://aclweb.org/anthology/I17-1030), [Scarton et al. (2018)](http://aclweb.org/anthology/L18-1553), and [Stajner and Nisioi (2018)](http://www.aclweb.org/anthology/L18-1479) generate sentence alignments (using different algorithms) only between adjacent article versions (i.e., 0-1, 1-2, 2-3, and 3-4). Meanwhile, [Scarton and Specia (2018)](http://aclweb.org/anthology/P18-2113) generate alignments between all versions (i.e., 0-{1,2,3,4}, 1-{2,3,4}, 2-{3,4}, and 3-4). The assumption behind using only adjacent versions is that, to write an article's simplification, an editor takes the immediately previous simplified version as basis (i.e., 0→1, 1→2, etc.). However, since the simplification manual followed by the Newsela editors is not public, it is not possible to corroborate that hypothesis.
+- [Alva-Manchego et al. (2017)](http://aclweb.org/anthology/I17-1030), [Scarton et al. (2018)](http://aclweb.org/anthology/L18-1553), and [Stajner and Nisioi (2018)](http://www.aclweb.org/anthology/L18-1479) generate sentence alignments (using different algorithms) only between adjacent article versions (i.e. 0-1, 1-2, 2-3, and 3-4). Meanwhile, [Scarton and Specia (2018)](http://aclweb.org/anthology/P18-2113) generate alignments between all versions (i.e., 0-{1,2,3,4}, 1-{2,3,4}, 2-{3,4}, and 3-4). The assumption behind using only adjacent versions is that, to write an article's simplification, an editor takes the immediately previous simplified version as basis (i.e. 0→1, 1→2, etc.). However, since the simplification manual followed by the Newsela editors is not public, it is not possible to corroborate that hypothesis.
 
 
 
-[Go back to the README](../README.md)
+[Go back to the README](../README.md)