Text Summarization Techniques: NLP Explained




A computer processing a large book into a concise summary

In the realm of Natural Language Processing (NLP), text summarization is a critical technique that aims to generate a concise and coherent summary of a larger text document. This technique is widely used in various applications such as news summarization, customer reviews summarization, and summarizing lengthy articles or documents.

The main goal of text summarization is to retain the key information from the original text while reducing the reading time, making it easier for users to understand the essence of the text in a shorter time.

Text summarization techniques can be broadly categorized into two types: extractive summarization and abstractive summarization. Extractive summarization involves identifying key phrases or sentences from the original text and combining them to form a summary.

On the other hand, abstractive summarization involves understanding the context and meaning of the text and generating a new summary, often with different words and phrases. This article will delve into these techniques, their methodologies, and how they are applied in NLP.

Extractive Summarization

Extractive summarization, as the name suggests, extracts key sentences or phrases from the source document to form the summary. This technique assumes that the most important information in a text document is contained in the key sentences and phrases. The challenge here is to identify these key elements. Various methods such as text ranking algorithms, machine learning models, and statistical methods are used to achieve this.

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One popular method for extractive summarization is the use of TextRank algorithm. This algorithm, inspired by Google’s PageRank, ranks sentences based on their importance. The sentences are represented as nodes in a graph, and the connections between them (based on their similarity) are represented as edges. The more connections a sentence has, the higher its rank, and the more likely it is to be included in the summary.

Machine Learning in Extractive Summarization

Machine learning models, particularly supervised learning models, have been extensively used in extractive summarization. These models are trained on a large corpus of text documents and their corresponding summaries. The model learns to identify the key sentences or phrases that are likely to appear in the summary. The features used for training these models can include the position of the sentence in the document, the frequency of the words, the presence of named entities, among others.

Unsupervised learning models, such as clustering algorithms, can also be used for extractive summarization. In this approach, sentences are grouped into clusters based on their similarity. The sentences that are closest to the centroid of their respective clusters are considered as the most representative of the cluster and are included in the summary.

Abstractive Summarization

Abstractive summarization, on the other hand, involves generating a new summary of the text that captures the main ideas in the original text. This is a more complex task as it requires a deep understanding of the text, the ability to infer, and the ability to generate coherent and grammatically correct sentences. This technique is similar to how humans summarize text, where we understand the context and express the main ideas in our own words.

Abstractive summarization can be achieved using sequence-to-sequence models, a type of model that is widely used in machine translation. These models consist of an encoder that encodes the input text into a fixed-length vector, and a decoder that generates the summary from this vector. The challenge here is to ensure that the generated summary is coherent, grammatically correct, and captures the main ideas of the text.

Deep Learning in Abstractive Summarization

Deep learning models, particularly Recurrent Neural Networks (RNNs) and more recently Transformer models, have shown great promise in abstractive summarization. These models are capable of capturing the long-term dependencies in the text, which is crucial for understanding the context and generating a coherent summary.

The Transformer model, introduced in the paper “Attention is All You Need”, has been particularly effective for this task. The model uses a mechanism called attention, which allows it to focus on different parts of the input sequence when generating the output sequence. This allows the model to generate a summary that is more coherent and closer to the original text in meaning.

Generative AI in Text Summarization

Generative AI, a subset of artificial intelligence that focuses on creating new content, has been increasingly used in text summarization. Generative models are capable of generating new text that is not present in the original document, making them suitable for abstractive summarization.

One of the most notable examples of generative AI in text summarization that we all know now is the use of Generative Pretrained Transformer 3 (GPT-3) model. This model, developed by OpenAI, is capable of generating human-like text based on the input provided. The model has been trained on a diverse range of internet text, allowing it to generate coherent and contextually relevant summaries.

Challenges and Future Directions

Despite the advancements in text summarization techniques, there are still several challenges that need to be addressed. One of the main challenges is ensuring the quality of the generated summary. The summary should not only be coherent and grammatically correct, but it should also accurately represent the main ideas of the original text. Evaluating the quality of the summary is also a challenge as it requires understanding the context and meaning of the text.

Another challenge is dealing with long documents. Most of the current techniques struggle with summarizing long documents as they have a limited memory capacity. Future research in text summarization could focus on developing techniques that can handle long documents and generate high-quality summaries.


In conclusion, text summarization is a crucial technique in NLP that helps in reducing the reading time and making the information more digestible. With the advancements in machine learning and deep learning techniques, the quality of the generated summaries has significantly improved. However, there are still several challenges that need to be addressed to further improve the quality of the summaries.

Generative AI, with its ability to generate new content, holds great promise for the future of text summarization. With further research and development, we can expect to see more advanced and high-quality text summarization techniques in the near future.

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