Book Image

Advanced Natural Language Processing with TensorFlow 2

By : Ashish Bansal, Tony Mullen
Book Image

Advanced Natural Language Processing with TensorFlow 2

By: Ashish Bansal, Tony Mullen

Overview of this book

Recently, there have been tremendous advances in NLP, and we are now moving from research labs into practical applications. This book comes with a perfect blend of both the theoretical and practical aspects of trending and complex NLP techniques. The book is focused on innovative applications in the field of NLP, language generation, and dialogue systems. It helps you apply the concepts of pre-processing text using techniques such as tokenization, parts of speech tagging, and lemmatization using popular libraries such as Stanford NLP and SpaCy. You will build Named Entity Recognition (NER) from scratch using Conditional Random Fields and Viterbi Decoding on top of RNNs. The book covers key emerging areas such as generating text for use in sentence completion and text summarization, bridging images and text by generating captions for images, and managing dialogue aspects of chatbots. You will learn how to apply transfer learning and fine-tuning using TensorFlow 2. Further, it covers practical techniques that can simplify the labelling of textual data. The book also has a working code that is adaptable to your use cases for each tech piece. By the end of the book, you will have an advanced knowledge of the tools, techniques and deep learning architecture used to solve complex NLP problems.
Table of Contents (13 chapters)
11
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12
Index

Viterbi decoding

A straightforward way to predict the sequence of labels is to output the label that has the highest activation from the previous layers of the network. However, this could be sub-optimal as it assumes that each label prediction is independent of the previous or successive predictions. The Viterbi algorithm is used to take the predictions for each word in the sequence and apply a maximization algorithm so that the output sequence has the highest likelihood. In future chapters, we will see another way of accomplishing the same objective through beam search. Viterbi decoding involves maximizing over the entire sequence as opposed to optimizing at each word of the sequence. To illustrate this algorithm and way of thinking, let's take an example of a sentence of 5 words, and a set of 3 labels. These labels could be O, B-geo, and I-geo as an example.

This algorithm needs the transition matrix values between labels. Recall that this was generated and stored...