Outline Morning program Preliminaries Semantic matching Learning to rank Entities Afternoon program Modeling user behavior Generating responses Recommender systems Industry insights Q & A 182
Outline Morning program Preliminaries Semantic matching Learning to rank Entities Afternoon program Modeling user behavior Generating responses One-shot dialogues Open-ended dialogues (chit-chat) Goal-oriented dialogues Alternatives to RNNs Resources Recommender systems Industry insights Q & A 183
Generating responses Tasks I Question Answering I Summarization I Query Suggestion I Reading Comprehension / Wiki Reading I Dialogue Systems I Goal-Oriented I Chit-Chat 184
Generating responses Example Scenario for machine reading task Sandra went to the kitchen. Fred went to the kitchen. Sandra picked up the milk. Sandra traveled to the o ffi ce. Sandra left the milk. Sandra went to the bathroom. I Where is the milk now? A: o ffi ce I Where is Sandra? A: bathroom I Where was Sandra before the o ffi ce? A: kitchen 185
Generating responses Example Scenario for machine reading task Sandra went to the kitchen. Fred went to the kitchen. Sandra picked up the milk. Sandra traveled to the o ffi ce. Sandra left the milk. Sandra went to the bathroom. I Where is the milk now? A: o ffi ce I Where is Sandra? A: bathroom I Where was Sandra before the o ffi ce? A: kitchen I’ll be going to Los Angeles shortly. I want to book a flight. I am leaving from Amsterdam. I want the return flight to be early morning. I don’t have any extra luggage. I wouldn’t mind extra leg room. I What does the user want? A: Book a flight I Where is the user flying from? A: Amsterdam I Where is the user going to? A: Los Angeles 186
Generating responses What is Required? I The model needs to remember the context I It needs to know what to look for in the context I Given an input, the model needs to know where to look in the context I It needs to know how to reason using this context I It needs to handle changes in the context A Possible Solution: I Hidden states of RNNs have memory: Run an RNN on the and get its representation to map question to answers/response. This will not scale as RNN states don’t have ability to capture long term dependency: vanishing gradients, limited state size. 187
Generating responses Teaching Machine to Read and Comprehend [Hermann et al., 2015] 188
Generating responses Neural Networks with Memory I Memory Networks I End2End MemNNs I Key-Value MemNNs I Neural Turing Machines I Stack/List/Queue Augmented RNNs 189
Generating responses End2End Memory Networks [Sukhbaatar et al., 2015] 190
Generating responses End2End Memory Networks [Sukhbaatar et al., 2015] I Share the input and output embeddings or not I What to store in memories individual words, word windows, full sentences I How to represent the memories? Bag-of-words? RNN reading of words? Characters? 191
Generating responses Attentive Memory Networks [Kenter and de Rijke, 2017] Framing the task of conversational search as a general machine reading task. 192
Generating responses Key-Value Memory Networks Example: for a KB triple [subject, relation, object], Key could be [subject,relation] and value could be [object] or vice versa. [Miller et al., 2016] 193
Generating responses WikiReading [Hewlett et al., 2016, Kenter et al., 2018] Task is based on Wikipedia data (datasets available in English, Turkish and Russian). I Categorical: relatively small number of possible answer (e.g.: instance of, gender, country). I Relational: rare or totally unique answers (e.g.: date of birth, parent,capital). 194
Generating responses WikiReading I Answer Classification : Encoding document and question, using softmax classifier to assign probability to each of to-50k answers (limited answer vocab) . I Sparse BoW Baseline, Averaged Embeddings, Paragraph Vector, LSTM Reader, Attentive Reader, Memory Network. I Generally models with RNN and attention work better, especially at relational properties. I Answer Extraction (labeling/pointing) For each word in the document, compute the probability that it is part of the answer. I Regardless of the vocabulary so the answer requires being mentioned in the document. I RNN Labeler: shows a complementary set of strengths, performing better on relational properties than categorical ones I Sequence to Sequence Encoding query and document and decoding the answer as sequences of words or characters. I Basic seq2seq, Placeholder seq2seq, Basic Character seq2seq, I Unifies the classification and extraction in one model: Greater degree of balance between relational and categorical properties. 195
Outline Morning program Preliminaries Semantic matching Learning to rank Entities Afternoon program Modeling user behavior Generating responses One-shot dialogues Open-ended dialogues (chit-chat) Goal-oriented dialogues Alternatives to RNNs Resources Recommender systems Industry insights Q & A 196
Generating responses Dialogue systems Dialogues/conversational agents/chat bots Open-ended dialogues Goal-oriented dialogues I ELIZA I Restaurant finding I Twitterbots I Hotel reservations I Alexa/Google home/Siri/Cortana I Set an alarm clock I Order a pizza I Play music I Alexa/Google home/Siri/Cortana Is this IR? 197
Generating responses Dialogue systems thanks Chit-chat bots fine am I machine user machine Hello how are you I am fine thanks user Straightforward seq-to-seq [Vinyals and Hello how are you Le, 2015]. ([Sordoni et al., 2015] is a precursor, but no RNN-to-RNN, and no LSTM). Same idea, but with attention [Shang et al., 2015] 198
Generating responses Dialogue systems Limitations Human : what is your job? I ’Wrong’ optimization criterion Machine : i’m a lawyer. I Generic responses Human : what do you do? I No way to incorporate world knowledge Machine : i’m a doctor. Example from [Vinyals and Le, I No model of conversation 2015] I Inconsistency I No memory of what was said earlier on Evaluation I Perplexity? I BLUE/METEOR? I Nice overview of How NOT To Evaluate Your Dialogue System [Liu et al., 2016]. I Open problem.... 199
Generating responses Dialogue systems 3 solutions I More consistency in dialogue with hierarchical network I Less generic responses with di ff erent optimization function I More natural responses with GANs 200
Generating responses Dialogue systems Hierarchical seq-to-seq [Serban et al., 2016]. Main evaluation metric: perplexity. 201
Generating responses Dialogue systems Avoid generic responses Usually: optimize log likelhood of predicted utterance, given previous context: C LL = arg max log p ( u t | context ) = arg max log p ( u t | u 0 . . . u t − 1 ) u t u t To avoid repetitive/boring answer ( I don’t know ), use maximum mutual information between previous context and predicted utterance [Li et al., 2015]. log p ( u t , context ) C MMI = arg max p ( u t ) p ( context ) u t = [derivation, next page . . . ] = arg max (1 − λ ) log p ( u t | context ) + λ log p ( context | u t ) u t 202
Generating responses Dialogue systems Bayes rule p ( context | u t ) p ( u t ) log p ( u t | context ) = log p ( context ) log p ( u t | context ) = log p ( context | u t ) + log p ( u t ) − log p ( context ) log p ( u t ) = log p ( u t | context ) − log p ( context | u t ) + log p ( context ) log p ( u t , context ) log p ( u t | context ) p ( context ) C MMI = arg max p ( u t ) p ( context ) = arg max p ( u t ) p ( context ) u t u t log p ( u t | context ) = arg max p ( u t ) u t = arg max log p ( u t | context ) − log p ( u t ) ← Weird, minus language model score. u t = arg max log p ( u t | context ) − λ log p ( u t ) ← Introduce λ . Crucial step! Without this it wouldn’t work. u t = arg max log p ( u t | context ) − λ ( log p ( u t | context ) − log p ( context | u t ) + log p ( context )) u t = arg max (1 − λ ) log p ( u t | context ) + λ log p ( context | u t ) u t (More is needed to get it to work. See [Li et al., 2015] for more details.) 203
Generating responses Generative adversarial network for dialogues I Discriminator network p( / ) I Classifier: real or generated utterance I Generator network Discriminator I Generate a realistic utterance Generator Real data Original GAN paper [Goodfellow et al., 2014]. Conditional GANs, e.g. [Isola et al., 2016]. 204
Generating responses Generative adversarial network for dialogues provided generated I Discriminator network I Classifier: real or generated utterance Generator I Generator network Hello how are you I am fine thanks I Generate a realistic utterance thanks am fine I p(x = real) Discriminator p(x = generated) See [Li et al., 2017] for more details. thanks Hello how are you am fine I Code available at https://github.com/jiweil/Neural-Dialogue-Generation 205
Generating responses Dialogue systems Open-ended dialogue systems I Very cool, current problem I Very hard I Many problems I Training data I Evaluation I Consistency I Persona I . . . 206
Outline Morning program Preliminaries Semantic matching Learning to rank Entities Afternoon program Modeling user behavior Generating responses One-shot dialogues Open-ended dialogues (chit-chat) Goal-oriented dialogues Alternatives to RNNs Resources Recommender systems Industry insights Q & A 207
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