908 research outputs found
State-of-the-art generalisation research in NLP: a taxonomy and review
The ability to generalise well is one of the primary desiderata of natural
language processing (NLP). Yet, what `good generalisation' entails and how it
should be evaluated is not well understood, nor are there any common standards
to evaluate it. In this paper, we aim to lay the ground-work to improve both of
these issues. We present a taxonomy for characterising and understanding
generalisation research in NLP, we use that taxonomy to present a comprehensive
map of published generalisation studies, and we make recommendations for which
areas might deserve attention in the future. Our taxonomy is based on an
extensive literature review of generalisation research, and contains five axes
along which studies can differ: their main motivation, the type of
generalisation they aim to solve, the type of data shift they consider, the
source by which this data shift is obtained, and the locus of the shift within
the modelling pipeline. We use our taxonomy to classify over 400 previous
papers that test generalisation, for a total of more than 600 individual
experiments. Considering the results of this review, we present an in-depth
analysis of the current state of generalisation research in NLP, and make
recommendations for the future. Along with this paper, we release a webpage
where the results of our review can be dynamically explored, and which we
intend to up-date as new NLP generalisation studies are published. With this
work, we aim to make steps towards making state-of-the-art generalisation
testing the new status quo in NLP.Comment: 35 pages of content + 53 pages of reference
Deep representation learning: Fundamentals, Perspectives, Applications, and Open Challenges
Machine Learning algorithms have had a profound impact on the field of
computer science over the past few decades. These algorithms performance is
greatly influenced by the representations that are derived from the data in the
learning process. The representations learned in a successful learning process
should be concise, discrete, meaningful, and able to be applied across a
variety of tasks. A recent effort has been directed toward developing Deep
Learning models, which have proven to be particularly effective at capturing
high-dimensional, non-linear, and multi-modal characteristics. In this work, we
discuss the principles and developments that have been made in the process of
learning representations, and converting them into desirable applications. In
addition, for each framework or model, the key issues and open challenges, as
well as the advantages, are examined
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Όλ¬Έ(λ°μ¬)--μμΈλνκ΅ λνμ :곡과λν μ»΄ν¨ν°κ³΅νλΆ,2020. 2. μ΄μꡬ.Recent advances in generation capability of deep learning models have spurred interest in utilizing deep generative models for unsupervised generative data augmentation (GDA). Generative data augmentation aims to improve the performance of a downstream machine learning model by augmenting the original dataset with samples generated from a deep latent variable model. This data augmentation approach is attractive to the natural language processing community, because (1) there is a shortage of text augmentation techniques that require little supervision and (2) resource scarcity being prevalent. In this dissertation, we explore the feasibility of exploiting deep latent variable models for data augmentation on three NLP tasks: sentence classification, spoken language understanding (SLU) and dialogue state tracking (DST), represent NLP tasks of various complexities and properties -- SLU requires multi-task learning of text classification and sequence tagging, while DST requires the understanding of hierarchical and recurrent data structures. For each of the three tasks, we propose a task-specific latent variable model based on conditional, hierarchical and sequential variational autoencoders (VAE) for multi-modal joint modeling of linguistic features and the relevant annotations. We conduct extensive experiments to statistically justify our hypothesis that deep generative data augmentation is beneficial for all subject tasks. Our experiments show that deep generative data augmentation is effective for the select tasks, supporting the idea that the technique can potentially be utilized for other range of NLP tasks. Ablation and qualitative studies reveal deeper insight into the underlying mechanisms of generative data augmentation. As a secondary contribution, we also shed light onto the recurring posterior collapse phenomenon in autoregressive VAEs and, subsequently, propose novel techniques to reduce the model risk, which is crucial for proper training of complex VAE models, enabling them to synthesize better samples for data augmentation. In summary, this work intends to demonstrate and analyze the effectiveness of unsupervised generative data augmentation in NLP. Ultimately, our approach enables standardized adoption of generative data augmentation, which can be applied orthogonally to existing regularization techniques.μ΅κ·Ό λ₯λ¬λ κΈ°λ° μμ± λͺ¨λΈμ κΈκ²©ν λ°μ μΌλ‘ μ΄λ₯Ό μ΄μ©ν μμ± κΈ°λ° λ°μ΄ν° μ¦κ° κΈ°λ²(generative data augmentation, GDA)μ μ€ν κ°λ₯μ±μ λν κΈ°λκ° μ»€μ§κ³ μλ€. μμ± κΈ°λ° λ°μ΄ν° μ¦κ° κΈ°λ²μ λ₯λ¬λ κΈ°λ° μ μ¬λ³μ λͺ¨λΈμμ μμ± λ μνμ μλ³Έ λ°μ΄ν°μ
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μ€νΈ λΆλ₯(text classification), μμ°¨μ λ μ΄λΈλ§κ³Ό λ©ν°νμ€νΉ κΈ°μ μ΄ νμν λ°ν μ΄ν΄(spoken language understanding, SLU), κ³μΈ΅μ μ΄λ©° μ¬κ·μ μΈ λ°μ΄ν° ꡬ쑰μ λν κ³ λ €κ° νμν λν μν μΆμ (dialogue state tracking, DST) λ± μΈ κ°μ§ λ¬Έμ μμ λ₯λ¬λ κΈ°λ° μμ± λͺ¨λΈμ νμ©ν λ°μ΄ν° μ¦κ° κΈ°λ²μ νλΉμ±μ λν΄ λ€λ£¬λ€. λ³Έ μ°κ΅¬μμλ 쑰건λΆ, κ³μΈ΅μ λ° μμ°¨μ variational autoencoder (VAE)μ κΈ°λ°νμ¬ κ° μμ°μ΄μ²λ¦¬ λ¬Έμ μ νΉνλ ν
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μ λ€λ£¨λ λ± ν λμ μ€νμ ν΅ν΄ λ₯ μμ± λͺ¨λΈ κΈ°λ° λ°μ΄ν° μ¦κ° κΈ°λ²μ ν¨κ³Όλ₯Ό ν΅κ³μ μΌλ‘ μ
μ¦νμλ€. λΆμμ μ°κ΅¬μμλ μκΈ°νκ·μ (autoregressive) VAEμμ λΉλ²ν λ°μνλ posterior collapse λ¬Έμ μ λν΄ νꡬνκ³ , ν΄λΉ λ¬Έμ λ₯Ό μνν μ μλ μ κ· λ°©μλ μ μνλ€. ν΄λΉ λ°©λ²μ μμ±μ λ°μ΄ν° μ¦κ°μ νμν 볡μ‘ν VAE λͺ¨λΈμ μ μ©νμμ λ, μμ± λͺ¨λΈμ μμ± μ§μ΄ ν₯μλμ΄ λ°μ΄ν° μ¦κ° ν¨κ³Όμλ κΈμ μ μΈ μν₯μ λ―ΈμΉ μ μμμ κ²μ¦νμλ€. λ³Έ λ
Όλ¬Έμ ν΅ν΄ μμ°μ΄μ²λ¦¬ λΆμΌμμ κΈ°μ‘΄ μ κ·ν κΈ°λ²κ³Ό λ³ν μ μ© κ°λ₯ν λΉμ§λ ννμ λ°μ΄ν° μ¦κ° κΈ°λ²μ νμ€νλ₯Ό κΈ°λν΄ λ³Ό μ μλ€.1 Introduction 1
1.1 Motivation 1
1.2 Dissertation Overview 6
2 Background and Related Work 8
2.1 Deep Latent Variable Models 8
2.1.1 Variational Autoencoder (VAE) 10
2.1.2 Deep Generative Models and Text Generation 12
2.2 Data Augmentation 12
2.2.1 General Description 13
2.2.2 Categorization of Data Augmentation 14
2.2.3 Theoretical Explanations 21
2.3 Summary 24
3 Basic Task: Text Classi cation 25
3.1 Introduction 25
3.2 Our Approach 28
3.2.1 Proposed Models 28
3.2.2 Training with I-VAE 29
3.3 Experiments 31
3.3.1 Datasets 32
3.3.2 Experimental Settings 33
3.3.3 Implementation Details 34
3.3.4 Data Augmentation Results 36
3.3.5 Ablation Studies 39
3.3.6 Qualitative Analysis 40
3.4 Summary 45
4 Multi-task Learning: Spoken Language Understanding 46
4.1 Introduction 46
4.2 Related Work 48
4.3 Model Description 48
4.3.1 Framework Formulation 48
4.3.2 Joint Generative Model 49
4.4 Experiments 56
4.4.1 Datasets 56
4.4.2 Experimental Settings 57
4.4.3 Generative Data Augmentation Results 61
4.4.4 Comparison to Other State-of-the-art Results 63
4.4.5 Ablation Studies 63
4.5 Summary 67
5 Complex Data: Dialogue State Tracking 68
5.1 Introduction 68
5.2 Background and Related Work 70
5.2.1 Task-oriented Dialogue 70
5.2.2 Dialogue State Tracking 72
5.2.3 Conversation Modeling 72
5.3 Variational Hierarchical Dialogue Autoencoder (VHDA) 73
5.3.1 Notations 73
5.3.2 Variational Hierarchical Conversational RNN 74
5.3.3 Proposed Model 75
5.3.4 Posterior Collapse 82
5.4 Experimental Results 84
5.4.1 Experimental Settings 84
5.4.2 Data Augmentation Results 90
5.4.3 Intrinsic Evaluation - Language Evaluation 94
5.4.4 Qualitative Results 95
5.5 Summary 101
6 Conclusion 103
6.1 Summary 103
6.2 Limitations 104
6.3 Future Work 105Docto
Backdoor Attacks and Countermeasures in Natural Language Processing Models: A Comprehensive Security Review
Deep Neural Networks (DNNs) have led to unprecedented progress in various
natural language processing (NLP) tasks. Owing to limited data and computation
resources, using third-party data and models has become a new paradigm for
adapting various tasks. However, research shows that it has some potential
security vulnerabilities because attackers can manipulate the training process
and data source. Such a way can set specific triggers, making the model exhibit
expected behaviors that have little inferior influence on the model's
performance for primitive tasks, called backdoor attacks. Hence, it could have
dire consequences, especially considering that the backdoor attack surfaces are
broad.
To get a precise grasp and understanding of this problem, a systematic and
comprehensive review is required to confront various security challenges from
different phases and attack purposes. Additionally, there is a dearth of
analysis and comparison of the various emerging backdoor countermeasures in
this situation. In this paper, we conduct a timely review of backdoor attacks
and countermeasures to sound the red alarm for the NLP security community.
According to the affected stage of the machine learning pipeline, the attack
surfaces are recognized to be wide and then formalized into three
categorizations: attacking pre-trained model with fine-tuning (APMF) or
prompt-tuning (APMP), and attacking final model with training (AFMT), where
AFMT can be subdivided into different attack aims. Thus, attacks under each
categorization are combed. The countermeasures are categorized into two general
classes: sample inspection and model inspection. Overall, the research on the
defense side is far behind the attack side, and there is no single defense that
can prevent all types of backdoor attacks. An attacker can intelligently bypass
existing defenses with a more invisible attack. ......Comment: 24 pages, 4 figure
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