d.md

D

D3.js : A JavaScript library for producing dynamic, interactive data visualizations in web browsers. D3.js makes use of the widely implemented Scalable Vector Graphics (SVG), HyperText Markup Language (HTML), and Cascading Style Sheets (CSS) standards. It is the successor to the earlier Protovis framework. In contrast to many other libraries, D3.js allows great control over the final visual result. D3.js was first released in 2011. † ℹ︎ d3js.org

DAD : → Disciplined Agile Delivery

Daemon : A computer program that runs as a background process, rather than being under the direct control of an interactive user. Traditionally, the process names of a daemon end with the letter “d”, for clarification that the process is in fact a daemon, and for differentiation between a daemon and a normal computer program. For example, syslogd is a daemon that implements system logging, and sshd is a daemon that serves incoming SSH connections. †

Daily Active Users : → Active Users

Daily Scrum : A daily Scrum event, time-boxed to 15 minutes, in which a Scrum Development Team plans the next development day. A Daily Scrum is not necessarily a “stand-up.”

DAM : → Digital Asset Management

Dark Mode : A color scheme that uses light-colored text, icons, and graphical user interface elements on a dark background. Light on dark color schemes require less energy to display on the most common display technologies. †

Dark pattern : A user interface that has been crafted to trick users into doing things. Another definition of a dark pattern is an instance where “user value is supplanted in favor of shareholder value.” The neologism “dark pattern” was coined in 2010 by Harry Brignull. † ℹ︎ darkpatterns.org

Darknet : The part of the Internet below the private Deep Web that uses custom software and hidden networks superimposed on the architecture of the Internet. “Darknet” was originally often associated with the Tor network. Anonymous communication between whistle-blowers, journalists, and news organizations is also facilitated by the “Darknet” Tor network. †

Dart : A client-optimized programming language for apps on multiple platforms. Dart is an object-oriented, class-defined, garbage-collected language using a C-style syntax that transcompiles optionally into JavaScript. It supports interfaces, mixins, abstract classes, reified generics, static typing, and a sound type system. Dart was released in 2011 by Google. † ℹ︎ dart.dev

Data : Individual units of information. A datum describes a single quality or quantity of some object or phenomenon. In analytical processes, data are represented by variables. Data is sometimes said to be transformed into information when it is viewed in context or in post-analysis. †

Data center : A dedicated space within a building, a building, or a group of buildings used to house computer systems and associated components, such as telecommunications and storage systems. A data center generally includes redundant or backup components and infrastructure for power supply, data communication connections, environmental controls (e.g., air conditioning, fire suppression), and various security devices. †

Data Control Language : A syntax similar to a computer programming language used to control access to data stored in a database (authorization). In particular, DCL is a component of Structured Query Language (SQL). †

Data Definition Language : A syntax similar to a computer programming language for defining data structures, especially database schemas. DDL statements create and modify database objects such as tables, indexes, and users. Common DDL statements are CREATE, ALTER, and DROP. †

Data lake : A system or repository of data stored in its natural or raw format, usually object blobs or files. A data lake is often a single store of data including raw copies of source system data, sensor data, social data, etc., and transformed data used for tasks such as reporting, visualization, advanced analytics, and machine learning. †

Data Manipulation Language : A computer programming language used for adding (inserting), deleting, and modifying (updating) data in a database. A DML is often a sublanguage of a broader database language such as SQL, with the DML comprising some of the operators in the language. Read-only selecting of data is sometimes distinguished as being part of a separate data query language (DQL), but it is closely related and sometimes also considered a component of a DML; some operators may perform both selecting (reading) and writing. †

Data Query Language : → Query language

Data storage : → Storage

Data Stream Management System : A computer software system to manage continuous data streams. A DSMS is similar to a database management system (DBMS), which is, however, designed for static data in conventional databases. A DSMS also offers flexible query processing so that the information needed can be expressed using queries. However, in contrast to a DBMS, a DSMS executes a continuous query that is not only performed once, but is permanently installed. Therefore, the query is continuously executed until it is explicitly uninstalled. †

Data swamp : A deteriorated and unmanaged data lake that is either inaccessible to its intended users or is providing little value. †

Data type : → Type

Data visualization : The graphic representation of data. Data visualization involves producing images that communicate relationships among the represented data to viewers of the images. This communication is achieved through the use of a systematic mapping between graphic marks and data values in the creation of the visualization. The mapping establishes how data values will be represented visually, determining how and to what extent a property of a graphic mark, such as size or color, will change to reflect changes in the value of a datum. To communicate information clearly and efficiently, data visualization uses statistical graphics, plots, information graphics, and other tools. Numerical data may be encoded using dots, lines, or bars, to visually communicate a quantitative message. Effective visualization helps users analyze and reason about data and evidence. It makes complex data more accessible, understandable, and usable. †

Data warehouse : A system used for data analysis and reporting, and a core component of business intelligence. Data warehouses are central repositories of integrated data from one or more disparate sources. They store current and historical data in one single place. †

data-* attribute : → Custom data attribute

Database : An organized collection of data, generally stored and accessed electronically from a computer system. Relational databases model data as rows and columns in a series of tables, and the vast majority use SQL for writing and querying data. Non-relational databases, also referred to as NoSQL, use different query languages. †

Database engine : The underlying software component that a database management system (DBMS) uses to create, read, update, and delete (CRUD) data from a database. Most database management systems include their own application programming interface (API) that allows the user to interact with their underlying engine without going through the user interface of the DBMS. The term “database engine” is frequently used interchangeably with “database server” or “database management system.” †

Database index : A data structure that improves the speed of data retrieval operations on a database table at the cost of additional writes and storage space to maintain the index data structure. Indexes can be created using one or more columns of a database table, providing the basis for both rapid random lookups and efficient access of ordered records. †

Database language : → Query language

Database Management System : A software system that enables users to define, create, maintain, and control access to a database. The “DBMS” acronym is sometimes extended to indicate the underlying database model, with RDBMS for the relational, OODBMS or ORDBMS for the object-oriented, and ORDBMS for the object-relational model. Other extensions can indicate some other characteristic, such as DDBMS for a distributed database management systems. †

Database server : A server which uses a database application to provide database services to other computer programs or computers. Database management systems frequently provide database server functionality, and some database management systems (such as MySQL) rely exclusively on this client–server model for database access (while others, like SQLite, are meant for use as an embedded database). †

DAU : → Daily Active Users

DAVE : → Delete, Add, View, Edit

DBC : → Design by Contract

DBMS : → Database Management System

DCE : → Dead code elimination

DCL : → Data Control Language

DCVS : → Distributed Concurrent Versions System

DDA : → Disability Discrimination Act

DDD : → Domain-Driven Design

DDL : → Data Definition Language

DDoS : Distributed → Denial of Service

Dead code elimination : A compiler optimization to remove code which does not affect the program results. Removing such code has several benefits: It shrinks program size, an important consideration in some contexts, and it allows the running program to avoid executing irrelevant operations, which reduces its running time. Dead code elimination can also enable further optimizations by simplifying program structure. Dead code includes code that can never be executed (unreachable code), and code that only affects dead variables (written to, but never read again), that is, irrelevant to the program. †

Dead letter queue : A queue that other queues can send messages that could not be processed successfully. Dead letter queues are useful to isolate unsuccessfully handled messages.

Debugging : The process of finding and resolving defects or problems within a computer program that prevent correct operation of application or system software. Debugging tactics can involve interactive debugging, control flow analysis, unit testing, integration testing, log file analysis, monitoring at the application or system level, memory dumps, and profiling. †

Declaration : In CSS, a declaration assigns a value of a property (or, in case of a shorthand, several values for several properties) to a selected element. A declaration is part of a declaration block as well as a rule. It consists of a property, a colon (:), and a value. If there are multiple declarations in a block, a semi-colon (;) must be inserted to separate each declaration. †

Declaration block : A block of zero or more CSS declarations and at-rules, enclosed by an opening ({) and a closing curly brace (}).

Decoration : The attempt to make a physical or virtual object more beautiful. Not to be confused with Design.

Decryption : The opposite of encryption, or the reverse process of it, moving from unintelligible ciphertext back to plain-text. †

Deep linking : The linking of a specific web resource or piece of web content rather than the respective website’s home page.

Deep Web : Parts of the World Wide Web whose contents are not indexed by standard web search engines. The opposite term to the Deep Web is the “Surface Web,” which is accessible to everyone using the Internet. The content of the Deep Web is hidden behind HTTP forms and includes many common uses such as web mail, online banking, private or otherwise restricted access social media pages and profiles, some web forums that require registration for viewing content, and services that users must pay for, and which are protected by paywalls, such as video-on-demand as well as online magazines and newspapers. The term “Deep Web” has first been used in 2001 by Michael K. Bergman. †

Defect : → Bug

Defect tracking system : → Bug tracking system

Definition of “Done” : A Scrum term that means a shared understanding of expectations that an increment must meet in order to be potentially releasable. The Definition of “Done” is mutually defined by the Development Teams of an organization’s Scrum Teams.

Delete, Add, View, Edit : A variation of CRUD. †

Demilitarized Zone : A physical or logical subnetwork that contains and exposes an organization’s external-facing services to an untrusted network, usually a larger network such as the Internet. The purpose of a DMZ is to add an additional layer of security to an organization’s local area network (LAN): An external network node can access only what is exposed in the DMZ, while the rest of the organization’s network is firewalled. †

Denial of Service : A cyber attack in which the perpetrator seeks to make a machine or network resource unavailable to its intended users by temporarily or indefinitely disrupting services of a host connected to the Internet. Denial of service is typically accomplished by flooding the targeted machine or resource with superfluous requests in an attempt to overload systems and prevent some or all legitimate requests from being fulfilled. †

Deno : A runtime for JavaScript and TypeScript that is based on the V8 JavaScript engine and the Rust programming language. It was created in 2018 by Ryan Dahl, original creator of Node.js, and is focused on security and productivity. Deno explicitly takes on the role of both runtime and package manager within a single executable, rather than requiring a separate package management program. † ℹ︎ deno.land

Dependency : → Coupling

Dependency injection : A technique whereby one object supplies the dependencies of another object. A “dependency” is an object that can be used, for example as a service. Instead of a client specifying which service it will use, something tells the client what service to use. The “injection” refers to the passing of a dependency (a service) into the object (a client) that would use it. The service is made part of the client’s state. Passing the service to the client, rather than allowing a client to build or find the service, is the fundamental requirement of the pattern. The intent behind dependency injection is to achieve separation of concerns of construction and use of objects. This can increase readability and code reuse. †

Dependency Inversion Principle : A specific form of decoupling software modules. When following this principle, the conventional dependency relationships established from high-level policy-setting modules to low-level dependency modules are reversed, thus rendering high-level modules independent of the low-level module implementation details. The principle states 1) that high-level modules should not depend on low-level modules, but that both should depend on abstractions (e.g., interfaces), and 2) that abstractions should not depend on details, but that details (concrete implementations) should depend on abstractions. †

Deployment : All of the activities that make a software system available for use. The general deployment process consists of several interrelated activities with possible transitions between them. Because every software system is unique, the precise processes or procedures within each activity are difficult to define. Therefore, deployment should be interpreted as a general process that has to be customized according to specific requirements or characteristics. †

Deployment environment : A computer system in which a computer program or software component is deployed and executed. In simple cases, such as developing and immediately executing a program on the same machine, there may be a single environment, but in industrial use the development environment (where changes are originally made) and production environment (what end users use) are separated; often with several stages in between. This structured release management process allows phased deployment (rollout), testing, and rollback in case of problems. †

Deprecated : → Deprecation

Deprecation : The discouragement of use of some terminology, feature, design, or practice, typically because it has been superseded or is no longer considered efficient or safe, without completely removing it or prohibiting its use. †

Descender : The portion of a letter that extends below the baseline of a font. †

Deserialization : The opposite of serialization, extracting a data structure or object state from a series of bytes. †

Design : A plan or specification for the construction of an object or system or for the implementation of an activity or process, or the result of that plan or specification in the form of a prototype, product, or process. The design usually has to satisfy certain goals and constraints, may take into account aesthetic, functional, economic, or socio-political considerations, and is expected to interact with a certain environment. †

Design by Contract : An approach for designing software. DBC prescribes that software designers should define formal, precise, and verifiable interface specifications for software components, which extend the ordinary definition of abstract data types with preconditions, postconditions, and invariants. These specifications are referred to as “contracts,” in accordance with a conceptual metaphor with the conditions and obligations of business contracts. The approach assumes all client components that invoke an operation on a server component will meet the preconditions specified as required for that operation. †

Design language : → Design system

Design system : A structured collection of design particles, elements, and components, alongside documentation and guidelines as well as, occasionally, code and tools.

Design strategy : The development and application of future-oriented design principles in order to increase an organization’s innovative and competitive qualities. Its foundations lie in the analysis of external and internal trends and data, which enables design decisions to be made on the basis of facts rather than aesthetics or intuition. Strategic design is regarded as an effective way to bridge innovation, research, management, and design. †

Design vocabulary : → Design system

Destructuring : A JavaScript expression that makes it possible to unpack values from arrays, or properties from objects, into distinct variables. ‡

Developer Experience : The experience developers have when they work with developer infrastructure, tools, and documentation. DX is similar to User Experience in that many UX guidelines also apply to DX, with the difference that the user is a developer.

Developer tools : Tools for web developers to test and debug their code. They are different from website builders and integrated development environments (IDEs) in that they do not assist in the direct creation of a web page, rather they are tools used generate, deploy, test, analyze, and optimize a website or application. † : → DevTools

Development and operations : → DevOps

Development Team : A Scrum role denoting a team that is responsible for managing and doing all the work required to prepare a releasable increment of software, and that knows and follows the Scrum values, roles, and events.

DevEx : → Developer Experience

Device orientation : The physical orientation of a hardware device. In the deviceorientation event specification, it is defined through three angles alpha (z-axis), beta (x-axis), and gamma (y-axis). ℹ︎ w3.org/TR/orientation-event

Device pixel : A reference to the physical pixels of a device.

DevOps : A set of practices that combines software development (Dev) and information-technology operations (Ops) which aims to shorten the systems development lifecycle and provide continuous delivery with high software quality. †

DevTools : → Chrome DevTools

DHCP : → Dynamic Host Configuration Protocol

DHTML : → Dynamic HTML

Dialog box : A graphical control element in the form of a small window that communicates information to the user and prompts them for a response. Dialog boxes are classified as “modal” or “modeless,” depending on whether they block interaction with the software that initiated the dialog. The type of dialog box displayed is dependent upon the desired user interaction. †

Digital Asset Management : Software that enables the respective owner and their delegates to perform operations on digital assets, providing a system that can store, organize, and share the managed data.

Digital Rights Management : A set of access control technologies for restricting the use of proprietary hardware and copyrighted works. DRM technologies try to control the use, modification, and distribution of copyrighted works (such as software and multimedia content), as well as systems within devices that enforce these policies. The use of digital rights management is not universally accepted. †

DIP : → Dependency Inversion Principle

Directionality : The direction in which a text is written.

Disability Discrimination Act : British accessibility regulations which have been repealed and replaced by the Equality Act 2010 (except in Northern Ireland where the Act still applies). †

Disciplined Agile Delivery : An approach to agile software development. DAD enables teams to make simplified process decisions around incremental and iterative solution delivery. It builds on the many practices espoused by advocates of agile software development, including Scrum, agile modeling, lean software development, and others. †

Display advertising : Graphic advertising on Internet websites, apps, or social media through banners or other advertising formats made of text, images, Flash, video, and audio. The main purpose of display advertising is to deliver general advertisements and brand messages to site visitors. †

Display resolution : The number of distinct pixels in each dimension that can be displayed. It can be an ambiguous term especially as the displayed resolution is controlled by different factors in cathode ray tube (CRT) displays, flat-panel displays (including liquid-crystal displays) and projection displays using fixed picture-element (pixel) arrays. It is usually quoted as width × height, with the units in pixels; for example, 1024×768 means the width is 1024 pixels and the height is 768 pixels. For device displays such as phones, tablets, monitors, and televisions, the use of the word “resolution” as defined is a misnomer, though common. The term “display resolution” is usually used to mean pixel dimensions which does not tell anything about the pixel density of the display on which the image is actually formed: Resolution properly refers to the pixel density, the number of pixels per unit distance or area, not the total number of pixels. In digital measurement, the display resolution would be given in pixels per inch (PPI). †

Distributed Concurrent Versions System : A distributed version control system that enables software developers working on locally distributed sites to efficiently collaborate on a software project. DCVS is based on Concurrent Versions System. †

Distributed Persistent Rendering : A generating or rendering of assets that is distributed between build and request time. DPR allows an asset cache to persist while other assets, which were not previously rendered, are being requested. The concept of DPR was coined in 2021 by Netlify.

Distributed Version Control System : A form of version control in which the complete code base, including its full history, is mirrored on every developer’s computer. This enables automatic management branching and merging, speeds up most operations (except pushing and pulling), improves the ability to work offline, and does not rely on a single location for backups. †

Dither : An intentionally applied form of noise used to randomize quantization error, preventing large-scale patterns such as color banding in images. Dither is routinely used in processing of both digital audio and video data. †

Divitis : Excessive use of div elements, an HTML anti-pattern.

Django : A Python-based web framework that follows the model-template-views (MTV) architectural pattern and whose primary goal is to ease the creation of complex, database-driven websites. The framework emphasizes reusability and “pluggability” of components, less code, low coupling, rapid development, and the principle of Don’t Repeat Yourself (DRY). Django was released in 2005; it is maintained by the Django Software Foundation (DSF). † ℹ︎ djangoproject.com

DKIM : → DomainKeys Identified Mail

DLR : → Dynamic Language Runtime

DMARC : → Domain-Based Message Authentication, Reporting, and Conformance

DML : → Data Manipulation Language

DMZ : → Demilitarized Zone

DNAME : A delegation name resource record in the Domain Name System (DNS). †

DNS : → Domain Name Service : → Domain Name System

DNS over HTTPS : A protocol for performing remote Domain Name System (DNS) resolution via the HTTPS protocol. A goal of the method is to increase user privacy and security by preventing eavesdropping and manipulation of DNS data through man-in-the-middle attacks by using the HTTPS protocol to encrypt the data between the DoH client and the DoH-based DNS resolver. DoH is specified in RFC 8484. †

DNS root zone : → Root zone

DNS spoofing : A form of computer security hacking in which corrupt Domain Name System data is introduced into the DNS resolver’s cache, causing the name server to return an incorrect result record, e.g., an IP address. This results in traffic being diverted to the attacker’s computer (or any other computer). †

DNSKEY : A DNS key resource record in the Domain Name System (DNS). †

DNSSEC : → Domain Name System Security Extensions

DocBook : A semantic markup language originally created for technical documentation. As a semantic language, DocBook documents do not describe what their contents “look like,” but rather the meaning of those contents. † ℹ︎ docbook.org

Docker : A set of Platform as a Service (PaaS) products that uses OS-level virtualization to deliver software in packages called containers. Containers are isolated from one another and bundle their own software, libraries, and configuration files; they can communicate with each other through well-defined channels. All containers are run by a single operating system kernel and therefore use fewer resources than virtual machines. The Docker software was first released in 2013 by Docker, the company. † ℹ︎ docker.com

DOCTYPE : An instruction that associates a particular SGML or XML document (for example, a web page) with a document type definition (for example, the formal definition of a particular version of HTML prior to HTML 5). In the serialized form of the document, the DOCTYPE manifests as a short string of markup that conforms to a particular syntax. The HTML layout engines in modern web browsers perform DOCTYPE sniffing or switching, wherein the DOCTYPE in a document served as text/html determines a layout mode, such as quirks or standards mode. Since web browsers are implemented with special-purpose HTML parsers, rather than general-purpose DTD-based parsers, they do not use DTDs and will never access them even if a URL is provided. The DOCTYPE is retained in HTML as a “mostly useless, but required” header only to trigger standards mode in common browsers. †

Document directive : A way to govern the properties of a document or worker environment to which a content security policy (CSP) applies. Document directives do not fall back to the default-src directive. ‡

Document Object Model : A cross-platform and language-independent interface that treats an XML or HTML document as a tree structure wherein each node is an object representing a part of the document. The DOM represents a document with a logical tree. Each branch of the tree ends in a node, and each node contains objects. DOM methods allow programmatic access to the tree; with them one can change the structure, style, or content of a document. Nodes can have event handlers attached to them. † ℹ︎ dom.spec.whatwg.org

Document Style Semantics and Specification Language : An international standard developed to provide style sheets for SGML documents. DSSSL consists of two parts: a tree transformation process that can be used to manipulate the tree structure of documents prior to presentation, and a formatting process that associates the elements in the source document with specific nodes in the target representation—the flow object tree. DSSSL is compatible with any SGML-based document type, but it has been used most often with DocBook. †

Document type declaration : → DOCTYPE

Document Type Definition : A set of markup declarations that define a document type for a SGML-family markup language (GML, SGML, XML, HTML). A DTD defines the valid building blocks of an XML document. It defines the document structure with a list of validated elements and attributes. A DTD can be declared inline inside an XML document, or as an external reference. †

Documentation : A set of documents provided in digital or analog media. Examples include user guides, white papers, online help, and quick-reference guides. †

DoH : → DNS over HTTPS

Dojo : A modular JavaScript library (or, more specifically, JavaScript toolkit) designed to ease the rapid development of cross-platform, JavaScript-based websites and applications. Dojo was first released in 2004. † ℹ︎ dojotoolkit.org

DOM : → Document Object Model

DOM clobbering : The injection of HTML into a web page with the goal of manipulating the DOM and escalating the injection to a cross-site scripting (XSS) attack. For example, one form of DOM clobbering uses an a element to overwrite a global variable for malicious purposes.

Domain : An administrative grouping of multiple private computer networks or hosts within the same infrastructure. Domains can be identified using a domain name; domains which need to be accessible from the public Internet can be assigned a globally unique name within the Domain Name System (DNS). †

Domain expert : → Subject-Matter Expert

Domain name : An identification string that defines a realm of administrative autonomy, authority, or control within the Internet. Domain names are used in various networking contexts and for application-specific naming and addressing purposes. In general, a domain name identifies a network domain, or it represents an Internet Protocol (IP) resource, such as a personal computer used to access the Internet, a server computer hosting a website, or the website itself or any other service communicated via the Internet. †

Domain name server : → Name server

Domain Name Service : → Domain Name System

Domain Name System : A hierarchical and decentralized naming system for computers, services, or other resources connected to the Internet or a private network. The DNS associates various information with domain names assigned to each of the participating entities. Most prominently, it translates more readily memorized domain names to the numerical IP addresses needed for locating and identifying computer services and devices with the underlying network protocols. By providing a worldwide distributed directory service, the Domain Name System has been an essential component of the functionality of the Internet since 1985. †

Domain Name System Security Extensions : A suite of extension specifications by the Internet Engineering Task Force (IETF) for securing data exchanged in the Domain Name System (DNS) in Internet Protocol (IP) networks. The protocol provides cryptographic authentication of data, authenticated denial of existence, and data integrity, but not availability or confidentiality. †

Domain sharding : The splitting of content across multiple subdomains. When multiple domains are used to serve multiple assets, browsers are able to download more resources simultaneously, resulting in a faster page load time and improved user experience. The problem with domain sharding, in terms of performance, is the cost of extra DNS lookups for each domain and the overhead of establishing each TCP connection. ‡

Domain-Based Message Authentication, Reporting, and Conformance : An email authentication protocol designed to give email domain owners the ability to protect their domain from unauthorized use, commonly known as email spoofing. The purpose and primary outcome of implementing DMARC is to protect a domain from being used in business email compromise attacks, phishing emails, email scams, and other cyber threat activities. Once a DMARC DNS entry is published, any receiving email server can authenticate the incoming email based on the instructions published by the domain owner within the DNS entry. DMARC was defined in 2015 in RFC 7489. †

Domain-Driven Design : The concept that the structure and language of software code (class names, class methods, class variables) should match the business domain. For example, if a software processes loan applications, it might have classes such as LoanApplication and Customer, and methods such as AcceptOffer and Withdraw. †

DomainKeys Identified Mail : An email authentication method designed to detect forged sender addresses in email (email spoofing), a technique often used in phishing and email spam. DKIM allows the receiver to check that an email claimed to have come from a specific domain was indeed authorized by the owner of that domain. It achieves this by affixing a digital signature, linked to a domain name, to each outgoing email message. The recipient system can verify this by looking up the sender’s public key published in the DNS. DKIM is an Internet Standard, defined in 2011 in RFC 6376, with updates in RFC 8301 and 8463. †

Don’t Repeat Yourself : A principle of software development aimed at reducing repetition of software patterns, replacing it with abstractions or using data normalization to avoid redundancy. The DRY principle is stated as “Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.” The principle has been introduced by Andy Hunt and Dave Thomas in their book The Pragmatic Programmer. †

Doorway page : A web page that is created for the deliberate manipulation of search engine indexes (spamdexing). A doorway page will affect the index of a search engine by inserting results for particular phrases while sending visitors to a different page. Doorway pages that redirect visitors without their knowledge use some form of cloaking. This usually falls under Black Hat SEO. †

DoS : → Denial of Service

Dot file : A file (or folder) that starts with a dot character (for example, .profile or .zshrc). It is treated as hidden, that is, the ls command does not display them unless the -a flag (ls -a) is used. In most command-line shells, wildcards will not match files whose names start with “.” unless the wildcard itself starts with an explicit “.”. A convention arose of using dotfiles in the user’s home directory to store per-user configuration or informational text. †

Dot notation : One of two ways to access object properties in JavaScript (objectName.propertyName), the other being bracket notation.

Dot-agnostic : A configuration aspect for email that allows dots (“.”) anywhere within the local-part of the email address, to still refer to the same address. That is, when dot-agnostic, [email protected], [email protected], and [email protected] would all be the same address and reach the same recipient.

Dots per inch : A measure of spatial printing, video, or image scanner dot density, in particular the number of individual dots that can be placed in a line within the span of 1 inch (2.54 cm). Similarly, the more newly introduced dots per centimeter (d/cm or dpcm) refers to the number of individual dots that can be placed within a line of 1 centimeter (≈ 0.393 in). †

Double : A double-precision, 64-bit floating-point data type.

Downstream : In version control, a repository that is based on or pulls from another repository. The work “flows downstream.”

Downtime : A period in which a system is unavailable. Downtime or outage duration refers to a period of time that a system fails to provide or perform its primary function. Reliability, availability, recovery, and unavailability are related concepts. Downtime is commonly applied to networks and servers. The common reasons for unplanned outages are system failures (such as a crash) or communications failures (commonly known as network outage). †

Downward compatibility : → Backward compatibility

DPI : → Dots per inch

DPR : → Distributed Persistent Rendering

DQL : → Data Query Language

Dreamweaver : A proprietary web design and development tool. Dreamweaver was created by Macromedia in 1997 and developed by them until Macromedia was acquired by Adobe in 2005. †

Driver : The code-writing role in pair programming.

DRM : → Digital Rights Management

DRY : → Don’t Repeat Yourself

DSMS : → Data Stream Management System

DSSSL : → Document Style Semantics and Specification Language

DTD : → Document Type Definition

Duck typing : An application of the duck test—“If it walks like a duck and it quacks like a duck, then it must be a duck”—to determine if an object can be used for a particular purpose. With normal typing, suitability is determined by an object’s type. In duck typing, an object’s suitability is determined by the presence of certain methods and properties, rather than the type of the object itself. †

Dup : → Duplicate (code)

Duplicate code : A sequence of source code that occurs more than once, either within a program or across different programs owned or maintained by the same entity. Duplicate code is generally considered undesirable. A minimum requirement is usually applied to the quantity of code that must appear in a sequence for it to be considered duplicate rather than coincidentally similar. Sequences of duplicate code are sometimes known as code clones or just clones, the automated process of finding duplication in source code is called clone detection. †

DVCS : → Distributed Version Control System

DW : → Data warehouse

DWH : → Data warehouse

DX : → Developer Experience

Dynamic : A type of website being dynamic on the server or on the client side. A server-side dynamic website is a website whose construction is controlled by an application server processing server-side scripts. In such scripting, parameters determine how the assembly of every new website proceeds, including the setting up of more client-side processing. A client-side dynamic website processes the website using HTML scripting running in the browser as it loads. JavaScript and other scripting languages determine the way the HTML in the received page is parsed into the Document Object Model, or DOM, that represents the loaded website. The same client-side techniques can then dynamically update or change the DOM in the same way. †

Dynamic Host Configuration Protocol : A network management protocol used on Internet Protocol (IP) networks for automatically assigning IP addresses and other communication parameters to devices connected to the network. DHCP eliminates the need for individually, manually configuring network devices. It consists of a centrally installed network DHCP server and client instances of the protocol stack on each computer or device. When connected to the network, and periodically thereafter, a client requests a set of parameters from the DHCP server using the DHCP protocol. †

Dynamic HTML : A collection of technologies used together to create interactive and animated websites by using a combination of a static markup language (such as HTML), a client-side scripting language (such as JavaScript), a presentation definition language (such as CSS), and the Document Object Model (DOM). The application of DHTML was introduced by Microsoft with the release of Internet Explorer 4 in 1997. †

Dynamic Language Runtime : A number of computer language services for dynamic languages. These services include a dynamic type system, dynamic method dispatch, dynamic code generation, and a hosting API. The DLR is used to implement dynamic languages on the .NET Framework, including the IronPython and IronRuby projects. It was first released in 2010 by Microsoft. † ℹ︎ github.com/IronLanguages/dlr

Dynamic password : → One-Time Password

Dynamic scope : Name resolution depending on the program state when the name is encountered, which is determined by the execution context (also called runtime context, calling context, or dynamic context). In dynamic scope, if a variable name’s scope is a certain function, then its scope is the time period during which the function is executing; while the function is running, the variable name exists, and is bound to its value, but after the function returns, the variable name does not exist. †

Dynamic typing : An interpreter’s assigning at runtime of a type to a variable, based on the variable’s value at the time. ‡

Dyslexia : A difficulty with reading despite normal intelligence. Different people are affected to varying degrees. Problems may include difficulties in spelling words, reading quickly, writing words, “sounding out” words in the head, pronouncing words when reading aloud, and understanding what one reads. †

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