Artificial intelligence and data

Hibernate (framework)

Hibernate ORM is an object/relational mapping library for Java, created by Gavin King in 2001, which maps Java classes to database tables and inspired the Java Persistence API.

Oct 22, 2026

Hidden fluid mechanics

Hidden fluid mechanics is a physics-informed deep-learning framework that infers fluid velocity and pressure fields from dye or smoke images, introduced at Brown University in 2018.

Hierarchical and recursive queries in SQL

Hierarchical and recursive queries in SQL are queries that traverse tree or graph data in relational tables, using recursive CTEs from SQL:1999 or Oracle's CONNECT BY.

Hierarchical clustering

Hierarchical clustering, also known as agglomerative clustering, is a family of cluster analysis methods that merge or split clusters to build a nested hierarchy shown as a dendrogram.

Hierarchical Data Format

Hierarchical Data Format (HDF) is a set of file formats and libraries for storing large scientific datasets, created at NCSA in 1987 and best known through its successor HDF5, implemented in 1998.

Hierarchical database model

The hierarchical database model is a data model that organizes records as a tree, enforcing one-to-many relationships, and formed the basis of IBM's IMS, released in 1968.

Hierarchical federated learning

Hierarchical federated learning (HFL) is a distributed machine learning method in which model updates are aggregated at edge servers between clients and the cloud, cutting communication.

Hierarchical navigable small world

Hierarchical navigable small world (HNSW) is a fully graph-based index for approximate nearest-neighbor search, introduced by Yu. A. Malkov and D. A. Yashunin in a 2018 IEEE paper.

Hierarchical reinforcement learning

Hierarchical reinforcement learning (HRL) structures an agent into layers of policies or subgoals so complex tasks decompose into reusable subtasks, using frameworks such as options, MAXQ, and HAMs.

High-Level Expert Group on Artificial Intelligence

The High-Level Expert Group on Artificial Intelligence (AI HLEG) is a 52-member expert group appointed by the European Commission in 2018 that drafted the EU's Ethics Guidelines for Trustworthy AI.

Highway network (machine learning)

A highway network is a deep neural network in which each layer has learned gates letting information pass unchanged, enabling training of networks hundreds of layers deep.

Hilbert spectral analysis is a signal processing method that computes instantaneous amplitude and frequency through the Hilbert transform, producing an energy–frequency–time distribution; with EMD it forms the Hilbert–Huang transform.

Hilbert–Huang transform

The Hilbert–Huang transform (HHT) is a two-stage signal processing method for nonlinear and nonstationary signals, reported by Norden Huang and colleagues in 1998, that yields an energy–frequency–time Hilbert spectrum.

Hill climbing

Hill climbing is a local search algorithm that repeatedly moves from the current solution to a better neighbor, stopping at a local maximum, which may not be the global optimum.

Hinge loss

The hinge loss is a convex loss function for binary classification, charging nothing once the prediction is correct with margin at least 1 and used by support vector machines.

Histogram equalization

Histogram equalization is an image-processing transform that increases contrast by remapping pixel intensities through the cumulative distribution function, spreading them over the full intensity range.

Histogram matching

Histogram matching, also called histogram specification, is an image processing technique that remaps pixel intensities so an image's histogram approximates a chosen target, generalizing histogram equalization.

Histogram of oriented gradients

The histogram of oriented gradients (HOG) is a feature descriptor in computer vision, introduced by Navneet Dalal and Bill Triggs in 2005 for detecting people in images.

History of artificial intelligence

The history of artificial intelligence records efforts to make machines perform intelligent tasks, from the 1956 Dartmouth workshop through deep learning and the large language model era.

History of Microsoft SQL Server

The history of Microsoft SQL Server began in 1989 as a licensed Sybase engine on OS/2, diverging after the 1994 split into an independent Windows and Linux product.

Hitachi Lumada

Hitachi Lumada is Hitachi's Internet of Things and digital innovation platform, launched in May 2016 to combine manufacturing operational technology with IT such as AI and big data analysis.

Oct 26, 2026

Hive Metastore

Hive Metastore (HMS): Apache Hive's metadata service storing table, partition, and location metadata in an RDBMS, served via Thrift (port 9083) to Spark, Trino, and other engines; standalone since Hive 3.0, with an Iceberg REST endpoint since 4.1.0.

Holland's schema theorem

Holland's schema theorem, or fundamental theorem of genetic algorithms, is John Holland's 1975 result giving a lower bound on a schema's expected instances after one generation of a genetic algorithm.

Homography (computer vision)

In computer vision, a homography is a projective transformation, represented by a 3×3 matrix, that maps points between planes, estimated from four point correspondences and used in panorama stitching, augmented reality, and document rectification.

Homography estimation

Homography estimation computes the 3×3 projective transformation that maps points between two images of a planar scene, underpinning image stitching, object detection, and camera calibration.

Homomorphic encryption

Homomorphic encryption, or privacy homomorphism, is encryption that permits computation directly on encrypted data without the secret key; Craig Gentry's 2009 lattice-based scheme made it practical.

Honey badger algorithm

The honey badger algorithm (HBA) is a nature-inspired metaheuristic for numerical optimization that mimics honey badger foraging, introduced by Fatma A. Hashim and colleagues in 2021.

Hopfield network

The Hopfield network, or Hopfield model, is a recurrent neural network proposed by John Hopfield in 1982 that stores patterns as energy minima and completes partial or noisy cues.

Oct 26, 2026

Hopsworks

Hopsworks (Hopsworks AB, Stockholm) is an open-source MLOps platform and AI Lakehouse, also known as the Hopsworks Feature Store, built on RonDB, HopsFS, and Kafka for feature, training, and inference pipelines.