Artificial intelligence and data

Classification tree

A classification tree is a supervised machine learning method that predicts a class label by recursively splitting data on feature tests, assigning a class at each leaf.

Claw-free graph

A claw-free graph is a graph with no induced K1,3, the three-leaf star called the claw; it generalizes line graphs and admits polynomial-time stable set algorithms.

ClearML, formerly Allegro Trains, is an open-source end-to-end MLOps/LLMOps platform: experiment tracking, data versioning, orchestration, pipelines, and model serving, self-hosted or SaaS; Apache 2.0 SDK, SSPL server, latest v2.1.12 (Aug 2026).

Clearview AI

Clearview AI is an American technology company that sells facial recognition searches to law enforcement from a database of more than 70 billion images scraped from the public internet.

Cleverbot

Cleverbot is a web-based chatbot created by British programmer Rollo Carpenter, online since 2006, that answers by searching its database of past human conversations rather than following pre-programmed rules.

ClickBench

ClickBench is an open-source benchmark of analytical (OLAP) databases from ClickHouse: 43 SQL queries over the 100-million-row Yandex.Metrica hits dataset, with public results for over 60 DBMS on AWS c6a.4xlarge.

ClickHouse

ClickHouse is an open-source, column-oriented database management system for online analytical processing, created at Yandex, released under the Apache 2 license in 2016, and developed since 2021 by ClickHouse, Inc.

ClinVar

ClinVar is a free public archive maintained by NCBI at the National Institutes of Health that records classifications of human genomic variants for inherited disease, cancer, and drug response.

Clonal selection algorithm

The clonal selection algorithm is an optimization method inspired by the immune system, cloning and mutating the best candidate solutions; the best-known version is CLONALG.

Closed-circuit television

Closed-circuit television (CCTV) is the use of video cameras to send a signal to a limited set of monitors, most often for surveillance and security.

Cloud data warehouse

Cloud data warehouse: a managed cloud service for storing and analyzing structured and semi-structured data (also called enterprise data warehouse, EDW). Key traits: elastic storage-compute separation, MPP and columnar stores, ETL/ELT ingestion, usage-based pricing; began with Amazon Redshift in 2012, now led by Snowflake, BigQuery, Databricks, Redshift.

Cloud database

A cloud database is a database deployed, delivered, and accessed through a cloud computing platform rather than on-premises hardware, either self-managed on a cloud virtual machine or consumed as a managed database-as-a-service.

Cloud Firestore

Cloud Firestore is a serverless NoSQL document database from Google, offered through Firebase and Google Cloud Platform, that syncs data in real time to mobile and web clients.

Cloud model (uncertainty reasoning)

The cloud model is a computational intelligence method, formulated by Deyi Li and colleagues, that converts between qualitative concepts and quantitative data while treating fuzziness and randomness together.

Cloudera

Cloudera is an American enterprise data software company founded in 2008 as the first commercializer of Apache Hadoop; based in San Jose, California, it went private in 2021.

Cluster analysis

Cluster analysis, also known as data clustering, is an unsupervised data mining task that groups unlabeled observations so similar ones share a cluster, using methods such as k-means and DBSCAN.

Clustered federated learning

Clustered federated learning is a distributed machine learning approach that groups clients with similar data distributions into clusters and trains a separate model for each cluster instead of one global model.

GeneralOct 21, 2026

Clustering Algorithms

Clustering algorithms are computational techniques that group unlabeled data so items in the same cluster are more alike each other than items elsewhere, the main tool of unsupervised learning.

Clustering coefficient

The clustering coefficient is a network science measure of how densely a node's neighbors are connected to each other, computed as the fraction of triangles that exist.

CNN-BiLSTM model

A CNN-BiLSTM model is a hybrid deep learning architecture in which convolutional layers extract local features and a bidirectional LSTM encodes temporal context, applied to forecasting, text classification, and anomaly detection.

CNN-LSTM

A CNN-LSTM is a hybrid deep learning architecture where convolutional layers extract spatial features from each step of a sequence and LSTM layers model how those features evolve over time.

Co-clustering

Co-clustering, also known as biclustering, is a data-mining technique that clusters the rows and columns of a matrix simultaneously, used in text mining and gene-expression analysis.

Co-simulation

Co-simulation is a simulation technique in which several specialized simulators, each modeling part of a coupled multi-domain system, run together and exchange data at synchronized points in time.

Co-training

Co-training is a semi-supervised machine learning algorithm, proposed by Avrim Blum and Tom Mitchell in 1998, in which two classifiers on different feature views teach each other with pseudo-labels.

Coalesce (company)

Coalesce (Coalesce.io) is a San Francisco data transformation, cataloging, and quality company founded in 2020 by Armon Petrossian and Satish Jayanthi; it raised $81M total and acquired CastorDoc and SYNQ.

CockroachDB

CockroachDB is a distributed SQL database developed by Cockroach Labs since 2015, replicating data across clusters so it tolerates machine and datacenter failures, with a PostgreSQL-compatible SQL interface.

COCO Captions

COCO Captions is a large-scale dataset of over 1.5 million human-written captions describing over 330,000 images, published in 2015 as the captioning extension of Microsoft COCO.

Cognitive computer

A cognitive computer, also known as a neuromorphic chip, is a computer system that simulates human thought and learning, exemplified by IBM's Watson, which won Jeopardy! in 2011.

Cold start (recommender systems)

Cold start is the problem a recommender system faces when it must recommend for a new user or item that has no interaction history, so collaborative filtering has nothing to learn from.