Artificial intelligence and data

Ranking

Ranking, also called league tables, is the task of ordering items so the most relevant or important appear first, central to information retrieval and search engines.

Rapidly exploring random tree

The rapidly exploring random tree (RRT) is a sampling-based motion planning algorithm that grows a tree of feasible configurations toward random samples to find paths.

RapidMiner

RapidMiner is a data science and machine learning software platform, begun as the open-source tool YALE, in which users build analyses as visual workflows of operators without writing code.

Rasa (software)

Rasa is an open-source, self-hostable platform for building conversational AI assistants and agents, released as Python libraries in 2016 and now built around its CALM dialogue system.

Rate of convergence, also known as speed of convergence, is a numerical analysis characterization of how quickly a sequence of approximations approaches its limit, predicting iterations needed for a target accuracy.

Rate–distortion optimization

Rate–distortion optimization (RDO) is an encoder-control technique in video and image coding that picks coding modes by minimizing reconstruction distortion subject to a bit-rate constraint, using the Lagrangian cost J = D + λ·R.

Ray casting

Ray casting is a rendering technique that casts one ray per pixel from the eye and sets the pixel's color from the first surface or volume samples it meets.

Reachability analysis

Reachability analysis is a formal verification method that computes the set of states a dynamical system can enter, certifying safety by checking that reachable states avoid unsafe regions.

Reactive synthesis

Reactive synthesis is a formal methods technique that automatically constructs a controller, circuit, or transducer from a temporal logic specification, guaranteed correct no matter how its environment behaves.

Reactome

Reactome is a free, open-access, peer-reviewed knowledgebase describing human biology as a network of molecular pathways, founded in 2003 and led from the Ontario Institute for Cancer Research.

REACTOR (expert system)

REACTOR was an expert system developed by William R. Nelson at EG&G Idaho to help reactor operators diagnose and treat nuclear accidents, presented in 1982.

Readers–writers problem

The readers–writers problem is a classical concurrency problem, posed in 1971 by Courtois, Heymans, and Parnas, in which readers share a resource while writers need exclusive access.

Readings in Database Systems

Readings in Database Systems, the "Red Book," is an edited anthology of classic database research papers in five editions (1988-2015), edited by Stonebraker, Hellerstein, and later Bailis, used in graduate database courses.

Real ID Act

The Real ID Act is a 2005 US federal law setting minimum security standards for state driver's licenses and IDs accepted for federal purposes, such as boarding aircraft.

Real-ESRGAN

Real-ESRGAN is an open-source image and video restoration model that extends ESRGAN to real photographs, created by Xintao Wang and colleagues at Tencent ARC Lab in 2021.

Real-time analytics

Real-time analytics analyzes data as it arrives, in milliseconds to seconds, via event streams, Kafka-style ingestion, streaming or OLAP platforms, unlike batch analytics, supporting fraud detection and AI.

Real-time optimization

Real-time optimization (RTO) is a model-based method that repeatedly re-solves a plant's steady-state economic optimization using current measurements, sending optimal setpoints to lower control layers.

Real-time simulation

Real-time simulation is a computational method that produces one second of simulated results in one second of wall-clock time, used to train operators, test controllers, and validate digital twins.

Recommender system

A recommender system, also called a recommendation system or recommendation engine, is software that suggests items a user is likely to value, used by Google, Netflix, and Amazon.

Record (computer science)

In computer science, a record, also known as a struct, is a data structure that groups a fixed set of named fields into a single object.

Rectifier (neural networks)

The rectifier, best known as the rectified linear unit or ReLU, is an activation function that outputs positive inputs unchanged and zero otherwise, and became the default nonlinearity of deep learning.

Recurrent convolutional neural network

A recurrent convolutional neural network, also called a convolutional recurrent network, combines convolutional layers with recurrent connections to process data structured in space and time, such as video and speech.

Recurrent neural network

A recurrent neural network (RNN) is a neural network that processes sequences one step at a time while keeping an internal hidden state that carries information forward.

Recursive filtering

A recursive filter computes each output from the current measurement and the previous estimate, matching full-history accuracy with fixed cost, as in IIR filters and the Kalman filter.

Recursive neural network

A recursive neural network is a neural architecture that applies the same composition function recursively over structured inputs such as parse trees, producing hierarchical vector representations used in natural language processing.

Red–black tree

A red–black tree, or symmetric binary B-tree, is a self-balancing binary search tree invented by Rudolf Bayer in 1972 and used in Java's TreeMap, C++ std::map, and the Linux kernel.

Redaction

Redaction is the removal or blocking out of sensitive, identifying, or otherwise non-disclosable information from documents and datasets before they are released, especially in government contexts.

Redash

Redash is an open-source, BSD-2-Clause SQL analytics and dashboarding platform (Flask, React, PostgreSQL, Redis/RQ) started in 2013, acquired by Databricks in 2020, with 45+ data sources, a QRDS in-memory SQLite feature, and releases resumed in 2025 after a three-year gap.

Redis

Redis (Remote Dictionary Server) is an open-source, in-memory data structure store used as a database, cache, message broker, and streaming engine, created by Salvatore Sanfilippo in 2009.