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All articles starting with D

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Data retention

Data retention, in communications law, requires providers to store traffic and location metadata for law enforcement; the EU's 2006 Directive was annulled by the CJEU in 2014.

Data Retention Directive

The Data Retention Directive, formally Directive 2006/24/EC, required EU telecom providers to retain traffic and location data for up to two years, and was invalidated by the Court of Justice in 2014.

Data science

Data science is the field combining domain expertise, programming skills, and mathematics and statistics to extract meaningful insights, spanning capture, preparation, analysis, visualization, and action.

Data scientist

Data scientist (SOC 15-2051), title coined in 2008 by DJ Patil and Jeff Hammerbacher: a professional applying statistics, machine learning, and programming to extract insights from data. U.S. median wage $120,230 (May 2025); BLS projects 35 percent growth 2025-2035.

Data scraping

Data scraping is a computing technique that automatically extracts data from websites by parsing rendered HTML, converting it into structured records for analysis or machine learning.

Data Security Law

The Data Security Law of the People's Republic of China (中华人民共和国数据安全法, DSL) is a national statute regulating data handling activities in China, effective September 1, 2021.

Data segment

The data segment is the part of a program's memory holding writable global and static variables, split into the initialized .data section and the zero-filled .bss section.

Data selection via influence functions and data attribution

Data selection via influence functions and data attribution, also called data valuation, estimates each training example's effect on a model and uses those estimates to select training data.

Data service level agreement

Data service level agreement (data SLA): a formal commitment between data teams and data consumers on freshness, availability, quality, and completeness targets, with SLO-backed metrics and remedies such as service credits when targets are missed.

Data set

A data set (dataset) is an organized collection of data, ranging from basic tabular tables to non-tabular forms like XML or images, and is critical for machine learning.

Data sharing

Data sharing: making data available across teams, companies, science, health, and government. Covers zero-copy exchange, cloud platforms like Redshift and BigQuery sharing, privacy-preserving methods, and governance standards.

Data silo

Data silo: an isolated data repository controlled by one department or unit, inaccessible to the rest of an organization (also information silo). Caused by legacy systems, structure, culture, and weak governance; a persistent barrier to analytics and AI, addressed through governance, integration, and data fabric/mesh architectures.

Data skew

Data skew: uneven distribution of data across partitions in distributed systems such as Spark, causing straggler tasks. Caused by hot keys, NULLs, low-cardinality joins; detected via task-duration metrics; fixed by AQE, salting, broadcast joins.

Data steward

A data steward, or data stewardship role, is the person responsible for day-to-day data quality, documentation, and policy adherence on behalf of a data owner.

Data storage

Data storage, also known as information storage or data storage technology, is the retaining of digital information in a physical medium like a hard disk, SSD, or tape.

Data stream mining

Data stream mining is a family of machine learning methods that build predictive models from continuous, high-volume data streams, where each example is inspected once and discarded.

Data structure

A data structure is a way of organizing information in a computer's memory so a program can use it efficiently, with the choice of structure determining whether the program runs fast or slow.

Data structure alignment

Data structure alignment, also called data alignment or memory alignment, is the requirement that data sit at addresses divisible by its size, with padding inserted by compilers.

Data swamp

Data swamp: a data lake degraded by missing metadata, ownership, and governance into an unusable store; term arose alongside James Dixon's 2010 data lake concept, with measurable indicators such as metadata completeness below 40%.

Data transformation (statistics)

Data transformation in statistics is a function applied to data or a random variable, most often to stabilize variance, linearize relationships, or make skewed data more normal.

Data Tutashkhia

Data Tutashkhia (დათა თუთაშხია) is a novel by the Georgian writer Chabua Amirejibi, his most famous work, set in Georgia at the turn of the 20th century.

Data type

A data type is a classification of values in a programming language that specifies the possible values, the operations that apply to them, and how they are represented.

Data Universal Numbering System

The Data Universal Numbering System, or D-U-N-S, is a system of nine-digit business identifiers assigned by Dun & Bradstreet since 1963 to identify and link business locations worldwide.

Data URI scheme

The Data URI scheme, also known as Data URL, is a URI scheme defined in RFC 2397 in 1998 that embeds small files inline as URLs instead of pointing to a server.

Data validation

Data validation, also called data checking, is the process of checking that data meets requirements for type, format, range, and business meaning before a system uses or stores it.

Data vault

Data Vault is a Dan Linstedt data warehouse modeling pattern using hub, link, and satellite tables with insert-only history tracking. Data Vault 2.0 (2013) adds hash keys, automation, and agile methodology.

Data versioning

Data versioning (dataset version control) tracks dataset states created by reprocessing, correction, or appending, so any state can be uniquely cited and retrieved; methods span file naming, DVC tools, and RDA principles for reproducibility.

Data virtualization

Data virtualization: querying data across databases, warehouses, APIs, and files through a single logical interface while leaving it in place, without ETL copies; contrasts with data federation, virtual data warehouse, and EII.

Data warehouse

A data warehouse is a central repository that integrates data from multiple operational systems into a structured, historical form designed for analytics and reporting rather than day-to-day transaction processing.

Data warehouse automation

Data warehouse automation (DWA) uses software to generate and maintain warehouse models, ETL/ELT pipelines, documentation, and orchestration, including Data Vault and medallion architectures; rule-based and LLM methods automate design where sources expose consistent metadata.