Named

Entity Recognition (NER).

Named Entity Recognition (NER) is a subtask of Information Extraction that seeks to locate and classify named entities in text into predefined categories such as person names, organizations, locations, medical codes, time expressions, quantities, monetary values, percentages, etc.

Overview

Named Entity Recognition is a method of extracting the relevant information from a large amount of data by classifying those entities that have a proper name. It is a task that is traditionally solved by machine learning, especially supervised machine learning, and is a key aspect of Natural Language Processing (NLP).

Techniques

There are several techniques used in Named Entity Recognition, including:

• Rule-based Systems: These systems develop a set of rules to identify named entities in a text.
• Supervised Learning: This technique requires a labeled dataset to train a model, which can then be used to predict the named entities in new data.
• Semi-supervised Learning: This technique uses a small amount of labeled data and a large amount of unlabeled data for training.
• Unsupervised Learning: This technique does not require any labeled data for training. Instead, it identifies patterns in the data to predict the named entities.

Applications

Named Entity Recognition has a wide range of applications, including:

• Information Extraction: NER is used to extract structured information from unstructured data sources.
• Machine Translation: NER is used in machine translation to identify the entities in the text that should not be translated.
• Question Answering: NER is used in question answering systems to identify the entities in a question and in the potential answers.
• Sentiment Analysis: NER is used in sentiment analysis to identify the entities that the sentiment is expressed towards.

Challenges

Despite its many applications, Named Entity Recognition faces several challenges, including:

• Ambiguity: The same word can represent different entities in different contexts.
• Variation in language: The way entities are expressed can vary greatly between different languages, dialects, or even between different documents.
• Lack of labeled data: Supervised learning techniques require a large amount of labeled data, which is often difficult to obtain.

See Also

• Information Extraction
• Natural Language Processing
• Machine Learning
• Artificial Intelligence