Why is Data Annotation for Machine Learning and AI Important?

Why is Data Annotation for Machine Learning and AI Important?
Machine learning

Data annotation for machine learning is often underestimated as an essential step in the overall process. Data annotation is the process of manually marking or labeling data. This way, you can use it to train machine learning algorithms.

Imagine you have a website selling books. You want to recommend other books based on customers' purchases. To do this, you need to know what each book looks like, what it contains (text or images), who wrote it, and so on. You can extract this information automatically using computer vision.

What is data annotation?

Data annotation is marking or labeling data to train machine learning algorithms. It is a part of the machine learning process. And it makes it possible for machines to "see" and understand data similarly to humans.

In other words, data annotation is data entry, labeling, and cataloging. It attaches metadata to help improve its performance in a machine-learning algorithm.

Building AI and ML technology

Data annotation is the first step in the ML lifecycle. It helps build any AI-powered technology. The purpose of data annotation is to give meaning to the data. This way, it can train machine learning algorithms.

Data annotation is a crucial part of the AI process. It comes under human-in-loop AI. It's not a one-time process but an ongoing activity throughout the ML lifecycle.

Data annotation is essential for machine learning and AI. It allows the machine to learn from and apply learning to other data. This process of using what you learned from one set of data to another is called supervised learning. Supervised learning is a form of machine learning. It's useful for various applications ranging from spam detection to medical diagnosis.

Almost every industry uses AI and ML. As a result, data annotation has become increasingly important. This trend will continue as more businesses adopt AI technologies for everyday operations.

Types of data annotation | Credits: labelmonkey

Types of data annotation

Data annotation for machine learning includes image annotation, video annotation, text annotation, and audio annotation. The first three types are the most common and most used in research. However, audio annotation is becoming more popular because of its importance for voice recognition systems.

Image Annotation

Image annotation involves labeling images with descriptive information. Image annotations require labeling objects and their position with bounding boxes. You can use it in computer vision and natural language processing (NLP). You can use this data for object detection, facial recognition, or emotion analysis.

Humans can complete image annotations, or you can automate them. For example, a deep convolutional neural network (CNN) can classify images as "person" or "no person." The system bases results on thousands of images with labeled captions.

Video Annotation

Label videos by attaching information to specific frames or areas of the video. Understand models in classifying the content of each frame to extract more meaningful knowledge from them.

Text Annotation

Text annotations on documents contain textual information from books or articles. Therefore, you could use them as training data for machine learning models that need text input. Examples include Natural Language Processing (NLP) algorithms or Question-Answer Systems (QAS).

Audio Annotations

These are like text annotations but on audio files. These annotations help improve speech recognition by providing input data. Examples include voice recordings intended to improve speech recognition systems. They provide more context information like speaker names or locations.

Data annotation in the machine learning process

Data annotation is an integral part of the machine learning process, making it possible for machines to "see" and understand images, videos, speech, and text similarly to humans. Data annotation is marking or labeling data to train machine learning algorithms.

For example, suppose you want to train a computer vision algorithm that detects whether an image contains a house using deep learning techniques like Convolutional Neural Networks (CNNs). In that case, you need to provide your machine with thousands of images labeled by humans as "house" or "no house." The same goes for speech recognition systems.

If you want your design to learn how phones are pronounced in English or German, you must provide some training data. You need experts who know how to articulate sounds by native speakers from different countries or regions around the globe.

Data annotation as part of the ML lifecycle

Data annotation is the first step in the ML lifecycle, which is a cyclical process with different phases, each with its data annotation task.

The ML lifecycle is a cyclical process with different phases, each with its data annotation task. The following figure shows the various steps in the ML lifecycle and how they relate to data annotation:

The stages of this cycle include:

  • Data preparation and cleaning
  • Preparation for model training
  • Model selection
  • Model training
  • Evaluation/testing
  • Deployment/Production

Data annotation for machine learning needs to be an ongoing process. The quality of your data sets will significantly impact how well your models perform, so it's essential to continually improve them by adding more annotations (e.g., additional data types and labels).

This process is also known as data augmentation. Data augmentation involves adding new data to your existing datasets, which you can use to improve the performance of machine learning models. For example, adding more images of handbags could help a model better identify different styles and colors.

Ensuring scalability with data annotation

Ensuring scalability with data annotation is a critical component of the ML lifecycle. As your data sets grow, it can be challenging to keep up with all the changes that need to happen. Data annotation is vital in ensuring your data sets are scalable. And not just for your organization but also for any partners sharing data with you.

In data annotation, scalability refers to efficiently handling large volumes of data. For example, suppose your company has generated millions of images in its dataset, but you have only 10 annotators available. In that case, your annotation job will take a long time—perhaps even months or years—to complete.

The solution? Automate as much as possible so that humans don't need to annotate every image manually. Data annotation aims to create training datasets representative of the target problem and large enough to support the various models in your machine-learning pipeline.


Data annotation helps machines to "see" and understand images, videos, speech, and text similarly to humans. This process's primary purpose is to ensure that machine learning algorithms are trained on high-quality data. It will help them learn from the training data and eventually improve their performance on real-world data.

When working on a project, you must get high-quality data annotations. You can't create the best product if your data is inaccurate or incomplete. KeyLab's AI-powered image and video annotation tool helps you annotate images and videos accurately and quickly. Use markers, bounding boxes, polygons, semantic segmentation, and more.