Tuple Type - A tuple type describes the structure of a tuple or record: its component attributes or fields and their associated types.
Tuple-versioning - Tuple-versioning retains multiple versions of a database row, or tuple, to represent changes over time.
Two-phase commit protocol - The two-phase commit protocol, or 2PC, coordinates an all-or-nothing decision for a transaction involving multiple transactional participants.
Two-phase locking - Two-phase locking, or 2PL, is a database concurrency-control protocol that divides each transaction's lock use into two phases.
Type - token distinction - The type - token distinction separates a repeatable kind or pattern from a particular instance of it.
Unavoidable Redundancy - Unavoidable redundancy is a descriptive term for repeated information that cannot simply be removed by a proposed normalization decomposition without losing...
Uncertain database - An uncertain database represents information whose value, existence or interpretation is not fully settled.
Uniform memory access - Uniform memory access, or UMA, is a shared-memory architecture in which processors have broadly uniform access characteristics to main memory, rather than...
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.
Universal IR Evaluation - Universal IR Evaluation refers here to a research approach for comparing information-retrieval outcomes through relationships among precision, recall...
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.
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...
Update Anomalies - Update anomalies are problems that arise when a database's representation of facts makes changes difficult, inconsistent or unintentionally destructive.
User-defined function - A user-defined function, or UDF, is a function supplied by a developer or user to perform a reusable operation beyond the system's existing built-in functions.
User modeling - User modeling is the process of building and maintaining a representation of a user's characteristics for a system's purposes.
User profile - A user profile is an organized representation of information associated with a user or user account for an application's purposes.
Value-Based Identity - Value-based identity distinguishes entities using selected attribute values that carry meaning in the modeled domain.
Vector Database - A vector database stores and retrieves data using numerical vectors, with facilities designed for similarity search and management of the associated records.
Vector-field consistency - Vector-field consistency, or VFC, is a research consistency model for replicated data that varies permitted replica divergence according to locality.
Verifiable computing - Verifiable computing enables a client to delegate a computation and check evidence that the returned result matches the specified computation on the...
Very large database - A very large database, or VLDB, is a database whose scale creates significant challenges for processing, administration and maintenance.
Very long instruction word - Very long instruction word, or VLIW, describes a processor architecture that exposes parallel execution opportunities to software through instructions or...
View - A view is a named database query that presents its result as a relation users can query much like a table.
Virtual directory - In directory integration, a virtual directory is a service that presents a logical directory view over information held in one or more underlying sources.
Virtual private cloud - A virtual private cloud, or VPC, is a logically isolated virtual networking environment within a cloud provider's infrastructure.
Virtual private server - A virtual private server, or VPS, is a virtualized server environment offered with an allocation of computing resources for running applications and services.
Visual analytics - Visual analytics combines computational analysis with interactive visual representations to support human reasoning about data.
Visual hierarchy - Visual hierarchy is the arrangement and emphasis of visual elements so people can recognize relative importance and relationships.
Visualization (graphics) - Visualization, in the graphics sense, is the creation of visual representations that help people understand information, data or a concept.
Vivification - In description-logic knowledge representation, vivification can mean replacing a disjunctive statement with a more manageable generalization, such as a...
Vocabulary-based transformation - Vocabulary-based transformation is an approach to translating data between systems by connecting their fields and values to shared meanings.
VSAN - VSAN means virtual storage area network, but the term has two important uses.
Web data integration - Web data integration is the process of bringing information from different web-accessible sources into a coherent form for use together.
White pages schema - A white pages schema is a data model for describing people in a directory service.
Whitelist - A whitelist, also called an allowlist, is a defined set of items that a system permits under a policy.
Wide-issue - Wide-issue describes a processor design capable of issuing multiple instructions or internal operations during one clock cycle.
Work stealing - Work stealing is a scheduling technique in which an idle worker takes available work from another worker's queue.
Workflow engine - A workflow engine is software that coordinates the execution of a defined process.
Write - write conflict - A write - write conflict occurs when concurrent operations or transactions try to modify the same data item in ways whose ordering matters.
WYSIWYM (interaction technique) - WYSIWYM, meaning What You See Is What You Meant in this interaction technique, lets people edit structured knowledge through natural-language feedback...
XML database - An XML database is a database designed to store, manage, and query information represented in XML, the Extensible Markup Language.
Yale shooting problem - The Yale shooting problem is a classic artificial-intelligence example showing how apparently reasonable default rules about persistence can produce...
Yo-yo (algorithm) - Yo-Yo is a distributed algorithm for finding the minimum identifier and electing a leader in a connected network represented by an undirected graph.