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What is Natural Language Understanding?

Natural Language Understanding is a subfield of Artificial Intelligence that deals with making human language understandable to machines. The challenges are to convert words and semantic sentences into numbers in such a way that their content and meaning are not lost.

What is Natural Language Understanding?

Natural Language Understanding (NLU for short) is a subarea of Natural Language Processing (NLP) and forms the basis for the following steps by ensuring that the algorithm understands natural, i.e. human, language correctly and well. This involves not only the actual understanding of word meaning but also semantic relationships in a sentence. This includes, for example, the different tenses (past or future) or that personal pronoun and their reference to a name are recognized correctly.

In the field of artificial intelligence, people often make the mistake of thinking that everything that is easy for us humans, such as communicating in a language, must also be easy for the computer. However, it is much more the case that the computer is very good at dealing with numbers. That is why it is so much better at things that are difficult for us humans, such as quickly calculating complex equations.

However, natural language is not in numbers, but in words. This means that in order for the computer to understand it, these words must first be converted into numbers and in these numbers, the meaning of the text must also be preserved. This is exactly the difficulty of Natural Language Understanding.

How does Natural Language Understanding work?

There are several disciplines in the field of NLU that contribute to the correct understanding of the content of the text by the computer. The quality of the individual models is also directly related so that each model has direct evaluations on the performance of the other.

  • Stemming and Lemmatization: Before we can start processing text, the words must first be converted into numbers. This could be done with the relatively simple approach of simply assigning a consecutive number to each word. However, this would not do justice to the complexity of our language by far. For example, it should reflect the fact that the words “play” and “played” are not the same thing, but are related in content and are clearly different from the word “car”. Therefore, concepts such as stemming and lemmatization are used to account for such connections.
Das Bild zeigt ein Beispiel für Overstemming.
Finding the Word Stem | Source: Author
  • Named Entity Recognition: When we process a sentence in the brain, we automatically orient ourselves to different entities in order to understand the meaning of the sentence. We can automatically assign which words might be names of people or places. In the field of artificial intelligence, there are special models that have been trained only to recognize entities.
  • Intent Detection: this subset of NLU tries to detect the intent of the text so that it can respond appropriately. For example, it makes a difference whether the customer is asking a question about the product or wants to initiate a complaint.

What are the differences between NLU and NLP?

The terms Natural Language Understanding and Natural Language Processing are often mistakenly confused. Natural Language Processing is a branch of Computer Science that deals with the understanding and processing of natural language, e.g. texts or voice recordings. The goal is to enable a machine to communicate with humans in the same way as humans have been doing for centuries.

Thus NLU is only one, albeit essential, part of NLP, which is the starting point for ensuring that the language was understood correctly. This also means that the quality of NLP depends immensely on how good the understanding of the text was. This is another reason why text comprehension is a major focus of research right now.

What are the applications of NLU?

Natural language understanding offers many new possibilities in a wide variety of areas. A selection of these is detailed here:

  • Speech Recognition tries to understand recorded speech and convert it into textual information. This makes it easier for downstream algorithms to process the speech. However, Speech Recognition can also be used on its own, for example, to convert dictations or lectures into text.
  • Customer service: Large companies receive a large number of inquiries every day via a wide variety of channels, such as e-mail or telephone. Often, these still have to be evaluated by humans in order to forward them to the processing department. A program that understands the content precisely can take over this distribution and the humans can take care of the more complex, downstream processes, such as a complaint.
  • Voice assistants: The well-known systems, including those from Amazon or Apple, are already in countless households and help customers operate their smart homes. However, the assistants also depend on correctly understanding human commands so that they can then derive the appropriate action.
  • Machine Translation: People often make the mistake of thinking that an automated translation of the text is comparatively easy since only the meaning has to be translated word by word. However, in almost every language there are words that can have multiple meanings. For example, the German word “umfahren” can mean both avoiding an obstacle and driving over it. So, in order to translate this word correctly, you need to understand the content of the preceding and following text and choose the correct meaning.

Which Models and Algorithms are used for Natural Language Understanding?

Natural Language Understanding encompasses a variety of models and algorithms to interpret human language. Let’s delve into the first eight models in more detail:

1. Rule-Based Systems:

Rule-based NLU systems rely on predefined linguistic rules and patterns to interpret a text. They use explicit instructions for tasks like named entity recognition (NER) and syntactic parsing. While straightforward, they may struggle with handling the complexity of language and evolving contexts.

2. Statistical Models:

Statistical NLU models employ probabilistic algorithms, such as Hidden Markov Models (HMM) and Conditional Random Fields (CRF), to analyze language. They excel at tasks like part-of-speech tagging and NER by learning patterns from data. However, they may require substantial labeled data for training.

3. Machine Learning Algorithms:

Machine learning algorithms like Support Vector Machines (SVM) and Random Forests are applied to various NLU tasks. They can classify text and extract information from it based on learned patterns. These models offer flexibility and adaptability to different NLU challenges.

Der Random Forest ist aus vielen einzelnen Decision Trees aufgebaut.
Example of a Random Forest | Source: Author

4. Deep Learning Models:

Deep learning has transformed NLU with models like Recurrent Neural Networks (RNNs), Convolutional Neural Networks (CNNs), and Transformers. RNNs are suitable for sequential data, while CNNs excel in text classification. Transformers, with their self-attention mechanism, have revolutionized many NLU tasks, offering context-rich understanding.

5. Word Embeddings:

Word embeddings, such as Word2Vec and GloVe, represent words as dense vectors. These embeddings capture semantic relationships between words, allowing NLU models to understand word meanings in context. They serve as fundamental building blocks for many NLU applications.

Word Embedding
Example of a 2-dimensional word embedding | Source: Author

6. Sequence-to-Sequence Models:

Sequence-to-sequence models, often based on RNNs or Transformers, are used for tasks like language translation and chatbot responses. They encode input sequences and generate corresponding output sequences, making them suitable for tasks requiring sequence-to-sequence transformations.

7. BERT (Bidirectional Encoder Representations from Transformers):

BERT is a pre-trained Transformer model renowned for its contextual language understanding. It captures bidirectional context, making it versatile for a wide range of NLU tasks. BERT has significantly advanced the field, especially in question answering and sentiment analysis.

8. GPT (Generative Pre-trained Transformer):

GPT is another pre-trained Transformer model known for its text generation capabilities. It uses a generative approach, predicting the next word in a sentence. GPT models have applications in chatbots, content generation, and creative text generation.

These eight models and algorithms represent a spectrum of NLU approaches, from rule-based systems and statistical methods to deep learning and pre-trained transformer models. Each has its strengths and limitations, making them suitable for different NLU tasks and contexts. Understanding these models is crucial for designing effective NLU solutions.

What are the challenges of Natural Language Understanding?

Natural Language Understanding is a field of artificial intelligence that deals with the comprehension of human language by machines. While significant progress has been made in recent years, NLU faces a multitude of complex challenges, highlighting the intricate nature of language and the difficulties in teaching machines to understand it fully.

One of the foremost challenges in NLU is ambiguity. Language is inherently ambiguous, and words often possess multiple meanings depending on the context in which they are used. Resolving this ambiguity accurately remains a significant challenge for NLU systems. For example, the word “bank” can refer to a financial institution or the side of a river, and understanding which meaning is intended requires context.

Context understanding is another crucial challenge. NLU systems must not only interpret individual words but also grasp the broader context in which those words are employed. This involves capturing nuances, idioms, and references to previous parts of a conversation, which can be quite intricate.

The variability in language usage poses another hurdle. Human language is incredibly diverse, encompassing dialects, slang, and regional expressions. NLU models must be versatile enough to understand and respond accurately to these various linguistic styles.

Named Entity Recognition is a vital task in NLU. It involves identifying and categorizing named entities such as names of people, places, and organizations. However, this task can be challenging due to the wide variety of entities and the lack of standardized naming conventions.

Sentiment analysis, which involves determining the emotional tone of a piece of text, presents its own set of challenges. NLU models must capture subtle nuances in sentiment, especially in longer texts or those with mixed sentiments.

Multilingual understanding is yet another complex aspect of NLU. While translating text between languages is one aspect, understanding the cultural and linguistic nuances in different languages poses a more intricate challenge.

Furthermore, a significant challenge arises from the lack of annotated data. Training NLU models requires substantial amounts of annotated data. However, for many languages and specialized domains, such data is scarce, making it difficult to develop accurate models.

Addressing these multifaceted challenges in NLU requires collaborative efforts from linguists, computer scientists, and data scientists. Researchers are continually working to develop more robust NLU models, improve training data quality, reduce biases, and enhance context understanding. While NLU technology holds the promise of enabling more natural and intuitive interactions between humans and machines, it is a journey fraught with complexities and exciting possibilities.

This is what you should take with you

  • Natural Language Understanding is a subfield of Artificial Intelligence and deals with understanding the content of natural language correctly and converting it into numbers so that it is understandable for a machine.
  • NLU uses various aspects to correctly understand the meaning of the text. These include stemming, named entity recognition, and intent detection.
  • The term should not be confused with Natural Language Processing. NLU is in fact a subfield of Natural Language Processing, which forms the basis for ensuring that the subsequent speech output is correctly selected.
  • NLU is already encountered in many applications today. For example, it can be used in customer service to correctly understand customer requests and forward them to the appropriate department.
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On Google Scholar you can find the latest papers in the field of Natural Language Understanding.

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