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Summarization

Summarization is the task of producing a shorter version of one or several documents that preserves most of the input's meaning.

Warning: Evaluation Metrics

For summarization, automatic metrics such as ROUGE and METEOR have serious limitations:

  1. They only assess content selection and do not account for other quality aspects, such as fluency, grammaticality, coherence, etc.
  2. To assess content selection, they rely mostly on lexical overlap, although an abstractive summary could express they same content as a reference without any lexical overlap.
  3. Given the subjectiveness of summarization and the correspondingly low agreement between annotators, the metrics were designed to be used with multiple reference summaries per input. However, recent datasets such as CNN/DailyMail and Gigaword provide only a single reference.

Therefore, tracking progress and claiming state-of-the-art based only on these metrics is questionable. Most papers carry out additional manual comparisons of alternative summaries. Unfortunately, such experiments are difficult to compare across papers. If you have an idea on how to do that, feel free to contribute.

CNN / Daily Mail

The CNN / Daily Mail dataset as processed by Nallapati et al. (2016) has been used for evaluating summarization. The dataset contains online news articles (781 tokens on average) paired with multi-sentence summaries (3.75 sentences or 56 tokens on average). The processed version contains 287,226 training pairs, 13,368 validation pairs and 11,490 test pairs. Models are evaluated with full-length F1-scores of ROUGE-1, ROUGE-2, ROUGE-L, and METEOR (optional).

Anonymized version

The following models have been evaluated on the entitiy-anonymized version of the dataset introduced by Nallapati et al. (2016).

Model ROUGE-1 ROUGE-2 ROUGE-L METEOR Paper / Source Code
RNES w/o coherence (Wu and Hu, 2018) 41.25 18.87 37.75 - Learning to Extract Coherent Summary via Deep Reinforcement Learning
SWAP-NET (Jadhav and Rajan, 2018) 41.6 18.3 37.7 - Extractive Summarization with SWAP-NET: Sentences and Words from Alternating Pointer Networks
HSASS (Al-Sabahi et al., 2018) 42.3 17.8 37.6 - A Hierarchical Structured Self-Attentive Model for Extractive Document Summarization (HSSAS)
GAN (Liu et al., 2018) 39.92 17.65 36.71 - Generative Adversarial Network for Abstractive Text Summarization
KIGN+Prediction-guide (Li et al., 2018) 38.95 17.12 35.68 - Guiding Generation for Abstractive Text Summarization based on Key Information Guide Network
SummaRuNNer (Nallapati et al., 2017) 39.6 16.2 35.3 - SummaRuNNer: A Recurrent Neural Network based Sequence Model for Extractive Summarization of Documents
rnn-ext + abs + RL + rerank (Chen and Bansal, 2018) 39.66 15.85 37.34 - Fast Abstractive Summarization with Reinforce-Selected Sentence Rewriting Official
ML+RL, with intra-attention (Paulus et al., 2018) 39.87 15.82 36.90 - A Deep Reinforced Model for Abstractive Summarization
Lead-3 baseline (Nallapati et al., 2017) 39.2 15.7 35.5 - SummaRuNNer: A Recurrent Neural Network based Sequence Model for Extractive Summarization of Documents
(Tan et al., 2017) 38.1 13.9 34.0 - Abstractive Document Summarization with a Graph-Based Attentional Neural Model
words-lvt2k-temp-att (Nallapti et al., 2016) 35.46 13.30 32.65 - Abstractive Text Summarization using Sequence-to-sequence RNNs and Beyond

Non-anonymized version

The following models have been evaluated on the non-anonymized version of the dataset introduced by See et al. (2017).

Model ROUGE-1 ROUGE-2 ROUGE-L METEOR Paper / Source Code
DCA (Celikyilmaz et al., 2018) 41.69 19.47 37.92 - Deep Communicating Agents for Abstractive Summarization
NeuSUM (Zhou et al., 2018) 41.59 19.01 37.98 - Neural Document Summarization by Jointly Learning to Score and Select Sentences
rnn-ext + RL (Chen and Bansal, 2018) 41.47 18.72 37.76 22.35 Fast Abstractive Summarization with Reinforce-Selected Sentence Rewriting Official
Bottom-Up Summarization (Gehrmann et al., 2018) 41.22 18.68 38.34 - Bottom-Up Abstractive Summarization Official
REFRESH (Narayan et al., 2018) 40.0 18.2 36.6 - Ranking Sentences for Extractive Summarization with Reinforcement Learning Official
ROUGESal+Ent RL (Pasunuru and Bansal, 2018) 40.43 18.00 37.10 20.02 Multi-Reward Reinforced Summarization with Saliency and Entailment
end2end w/ inconsistency loss (Hsu et al., 2018) 40.68 17.97 37.13 - A Unified Model for Extractive and Abstractive Summarization using Inconsistency Loss
rnn-ext + abs + RL + rerank (Chen and Bansal, 2018) 40.88 17.80 38.54 20.38 Fast Abstractive Summarization with Reinforce-Selected Sentence Rewriting Official
Lead-3 baseline (See et al., 2017) 40.34 17.70 36.57 22.21 Get To The Point: Summarization with Pointer-Generator Networks Official
Pointer + Coverage + EntailmentGen + QuestionGen (Guo et al., 2018) 39.81 17.64 36.54 18.54 Soft Layer-Specific Multi-Task Summarization with Entailment and Question Generation
Pointer-generator + coverage (See et al., 2017) 39.53 17.28 36.38 18.72 Get To The Point: Summarization with Pointer-Generator Networks Official

Gigaword

The Gigaword summarization dataset has been first used by Rush et al., 2015 and represents a sentence summarization / headline generation task with very short input documents (31.4 tokens) and summaries (8.3 tokens). It contains 3.8M training, 189k development and 1951 test instances. Models are evaluated with ROUGE-1, ROUGE-2 and ROUGE-L using full-length F1-scores.

Model ROUGE-1 ROUGE-2 ROUGE-L Paper / Source Code
Re^3 Sum (Cao et al., 2018) 37.04 19.03 34.46 Retrieve, Rerank and Rewrite: Soft Template Based Neural Summarization
CGU (Lin et al., 2018) 36.3 18.0 33.8 Global Encoding for Abstractive Summarization Official
Pointer + Coverage + EntailmentGen + QuestionGen (Guo et al., 2018) 35.98 17.76 33.63 Soft Layer-Specific Multi-Task Summarization with Entailment and Question Generation
words-lvt5k-1sent (Nallapti et al., 2016) 36.4 17.7 33.71 Abstractive Text Summarization using Sequence-to-sequence RNNs and Beyond
Struct+2Way+Word (Song et al., 2018) 35.47 17.66 33.52 Structure-Infused Copy Mechanisms for Abstractive Summarization
FTSum_g (Cao et al., 2018) 37.27 17.65 34.24 Faithful to the Original: Fact Aware Neural Abstractive Summarization
DRGD (Li et al., 2017) 36.27 17.57 33.62 Deep Recurrent Generative Decoder for Abstractive Text Summarization
SEASS (Zhou et al., 2017) 36.15 17.54 33.63 Selective Encoding for Abstractive Sentence Summarization
EndDec+WFE (Suzuki and Nagata, 2017) 36.30 17.31 33.88 Cutting-off Redundant Repeating Generations for Neural Abstractive Summarization
Seq2seq + selective + MTL + ERAM (Li et al., 2018) 35.33 17.27 33.19 Ensure the Correctness of the Summary: Incorporate Entailment Knowledge into Abstractive Sentence Summarization
Seq2seq + E2T_cnn (Amplayo et al., 2018) 37.04 16.66 34.93 Entity Commonsense Representation for Neural Abstractive Summarization
RAS-Elman (Chopra et al., 2016) 33.78 15.97 31.15 Abstractive Sentence Summarization with Attentive Recurrent Neural Networks
ABS+ (Rush et al., 2015) 29.76 11.88 26.96 A Neural Attention Model for Sentence Summarization *
ABS (Rush et al., 2015) 29.55 11.32 26.42 A Neural Attention Model for Sentence Summarization *

(*) Rush et al., 2015 report ROUGE recall, the table here contains ROUGE F1-scores for Rush's model reported by Chopra et al., 2016

DUC 2004 Task 1

Similar to Gigaword, task 1 of DUC 2004 is a sentence summarization task. The dataset contains 500 documents with on average 35.6 tokens and summaries with 10.4 tokens. Due to its size, neural models are typically trained on other datasets and only tested on DUC 2004. Evaluation metrics are ROUGE-1, ROUGE-2 and ROUGE-L recall @ 75 bytes.

Model ROUGE-1 ROUGE-2 ROUGE-L Paper / Source Code
DRGD (Li et al., 2017) 31.79 10.75 27.48 Deep Recurrent Generative Decoder for Abstractive Text Summarization
EndDec+WFE (Suzuki and Nagata, 2017) 32.28 10.54 27.8 Cutting-off Redundant Repeating Generations for Neural Abstractive Summarization
Seq2seq + selective + MTL + ERAM (Li et al., 2018) 29.33 10.24 25.24 Ensure the Correctness of the Summary: Incorporate Entailment Knowledge into Abstractive Sentence Summarization
SEASS (Zhou et al., 2017) 29.21 9.56 25.51 Selective Encoding for Abstractive Sentence Summarization
words-lvt5k-1sent (Nallapti et al., 2016) 28.61 9.42 25.24 Abstractive Text Summarization using Sequence-to-sequence RNNs and Beyond
ABS+ (Rush et al., 2015) 28.18 8.49 23.81 A Neural Attention Model for Sentence Summarization
RAS-Elman (Chopra et al., 2016) 28.97 8.26 24.06 Abstractive Sentence Summarization with Attentive Recurrent Neural Networks
ABS (Rush et al., 2015) 26.55 7.06 22.05 A Neural Attention Model for Sentence Summarization

Sentence Compression

Sentence compression produces a shorter sentence by removing redundant information, preserving the grammatically and the important content of the original sentence.

Google Dataset

The Google Dataset was built by Filippova et al., 2013(Overcoming the Lack of Parallel Data in Sentence Compression). The first dataset released contained only 10,000 sentence-compression pairs, but last year was released an additional 200,000 pairs.

Example of a sentence-compression pair:

Sentence: Floyd Mayweather is open to fighting Amir Khan in the future, despite snubbing the Bolton-born boxer in favour of a May bout with Argentine Marcos Maidana, according to promoters Golden Boy

Compression: Floyd Mayweather is open to fighting Amir Khan in the future.

In short, this is a deletion-based task where the compression is a subsequence from the original sentence. From the 10,000 pairs of the eval portion(repository) it is used the very first 1,000 sentence for automatic evaluation and the 200,000 pairs for training.

Models are evaluated using the following metrics:

  • F1 - compute the recall and precision in terms of tokens kept in the golden and the generated compressions.
  • Compression rate (CR) - the length of the compression in characters divided over the sentence length.
Model F1 CR Paper / Source Code
BiRNN + LM Evaluator (Zhao et al. 2018) 0.851 0.39 A Language Model based Evaluator for Sentence Compression https://github.com/code4conference/code4sc
LSTM (Filippova et al., 2015) 0.82 0.38 Sentence Compression by Deletion with LSTMs
BiLSTM (Wang et al., 2017) 0.8 0.43 Can Syntax Help? Improving an LSTM-based Sentence Compression Model for New Domains

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