Union Of Events - The union of events is the event that at least one of them occurs. For two events A and B, it is written A ∪ B and includes outcomes belonging to A, B or both.
Unique action axioms - Unique action axioms are logical statements that distinguish action names and their arguments in an action theory.
Unique key - A unique key is a column, or combination of columns, whose values distinguish records within a defined database scope.
Unique name assumption - The unique name assumption is a rule of interpretation under which different names denote different individuals.
Unique-names assumption - The unique-names assumption is the convention that different names denote different individuals.
Unit clause - A unit clause is a clause containing exactly one literal. A literal is an atomic proposition or its negation, so both P and ¬P are unit clauses.
Unit Gompertz distribution - The unit Gompertz distribution is a continuous probability distribution on the open interval from zero to one, constructed by an exponential transformation...
Unit preference - Unit preference is a strategy for directing a resolution theorem prover toward inferences involving a unit clause, which contains one literal.
Unit production - A unit production is a context-free grammar rule whose right-hand side consists of exactly one nonterminal symbol, such as A→B.
Unit propagation - Unit propagation is a logical simplification process that repeatedly applies assignments forced by unit clauses.
Unit resolution - Unit resolution is a resolution inference in which at least one parent clause contains exactly one literal.
Unit vector - A unit vector is a vector whose length is one under the chosen norm.
Unit Weibull distribution - The unit Weibull distribution is a continuous distribution on the open interval from zero to one, obtained by transforming a positive Weibull variable with...
Unit-weighted regression - Unit-weighted regression is a simple linear prediction approach that combines predictors using equal-magnitude weights, commonly after standardizing them...
Unitary matrix - A unitary matrix is a square complex-valued matrix whose conjugate transpose is its inverse.
Units function - A units function is a function used in a knowledge representation to connect a numerical value with a measurement unit and the quantity it denotes.
Univariate analysis - Univariate analysis examines one variable at a time to understand its values, distribution and other relevant properties.
Univariate design - A univariate design is an experimental design with one dependent variable or outcome.
Univariate feature selection - Univariate feature selection evaluates input features one at a time and selects those that score well under a chosen statistical criterion.
Universal approximation theorem - The universal approximation theorem refers to results showing that suitable neural-network families can approximate broad classes of functions as closely as...
Universal approximator theorem - The universal approximator theorem, more commonly called the universal approximation theorem, describes the expressive capacity of certain neural-network...
Universal code - A universal code, in this information-retrieval context, is an integer coding scheme with an efficiency guarantee across a specified class of source...
Universal code (data compression) - A universal code in data compression is a coding scheme designed to work across a specified class of sources without requiring the exact source...
Universal hashing - Universal hashing selects a hash function randomly from a family designed to limit collisions.
Universal Instantiation - Universal instantiation is an inference rule that applies a universally quantified statement to a particular term.
Universal IR Evaluation - Universal IR Evaluation refers here to a research approach for comparing information-retrieval outcomes through relationships among precision, recall...
Universal portfolio algorithm - The universal portfolio algorithm is an online portfolio-selection method introduced by Thomas Cover.
Universal psychometrics - Universal psychometrics is a research approach to measuring cognitive abilities across different kinds of systems, including humans, other animals...
Universal Relation Assumption - The universal relation assumption is a family of assumptions in relational database theory that treats the information of a database as describable through...
Universal Relation Schema - A universal relation schema is a conceptual relation schema containing all the attributes under consideration in a database-design problem.
Unknown Value - An unknown value is information that exists for the situation being described but is not known to the database or its users.
Unlabeled data - Unlabeled data is a collection of examples without known target answers for the learning task being considered.
Unlabeled example - An unlabeled example is one record containing input information without a known target answer for the task at hand.
Unlikelihood training - Unlikelihood training adds an objective that lowers the probability of selected undesirable outputs.
Unmatched count - Unmatched count refers to an indirect survey technique, also called the item count technique or list experiment, for estimating the prevalence of a...
Unnormalized form - Unnormalized form, often shortened to UNF, describes a data arrangement that has not been organized to meet first normal form in a conventional relational...
Unobserved heterogeneity in duration models - Unobserved heterogeneity in duration models means that units differ in their tendency to experience an event for reasons not captured by the observed...
Unrolling - Unrolling a dynamic Bayesian network means expanding its temporal template into an ordinary Bayesian network for a specified sequence of time steps.
Unscented Kalman filter - The unscented Kalman filter, or UKF, is a recursive state estimator that uses carefully selected sigma points to approximate how uncertainty passes through...
Unscented Kalman smoother - An unscented Kalman smoother estimates past hidden states using observations from an entire interval, applying sigma-point approximations to nonlinear state...
Unscented transform - The unscented transform is a deterministic method for approximating the mean and covariance of a random quantity after a nonlinear transformation.
Unsharp mask - An unsharp mask is a sharpening operation that compares an image with a blurred version and adds a scaled copy of their difference back to the original.
Unstructured data - Unstructured data is information whose substantive content is not organized into a predefined set of fields suitable for straightforward tabular analysis.
Unsupervised Biclustering - Unsupervised biclustering discovers related subsets of rows and columns in a data matrix without using target class labels to define those groups.
Unsupervised Clustering - Unsupervised clustering groups examples by patterns in their inputs without using predefined target labels to determine the groups.
Unsupervised learning - Unsupervised learning finds structure in data without using supplied target labels to guide the fitting objective.
Unsupervised parsing - Unsupervised parsing learns syntactic structure from sentences without using their reference parse trees as training targets.
Unsupervised Pretrained Network - An unsupervised pretrained network is a neural network whose parameters are first learned using an objective that does not require the eventual task's...