v.md

V

Validation : The process of ensuring data or code have undergone cleansing to ensure they have quality, that is, that they are both correct and useful. Validation uses routines, often called validation rules, validation constraints, or check routines, that check for the correctness, meaningfulness, and security of the data and code that are input to the system. The rules may be implemented through the automated facilities of a dictionary, or by the inclusion of explicit validation logic. †

Validator : A software used to check the validity or syntactical correctness of a fragment of code or document. The term is commonly used in the context of validating HTML, CSS, or XML documents like RSS feeds, though a validator can be used for any defined format or language. †

Value : The representation of some entity that can be manipulated by a program. The members of a type are the values of that type. In declarative (high-level) languages, values have to be referentially transparent. †

Value-Driven Design : A systems engineering strategy based on microeconomics which enables multidisciplinary design optimization. The terms “value-driven design” and “value-centric design” are used interchangeably. The essence of these strategies is that design choices are made to maximize system value rather than to meet performance requirements. VDD is similar to the value-driven approach of agile software development, where a project’s stakeholders prioritize their high-level needs (or system features) based on the perceived business value each would deliver. †

Variable : A storage address (identified by a memory address) paired with an associated symbolic name, which contains some known or unknown quantity of information referred to as a value. The variable name is the usual way to reference the stored value, in addition to referring to the variable itself, depending on the context. This separation of name and content allows the name to be used independently of the exact information it represents. The identifier in computer source code can be bound to a value during runtime, and the value of the variable may thus change during the course of program execution. † : → Custom property

Variable font : As OpenType variable fonts, an extension to the OpenType specification introduced in OpenType 1.8. In 2016, Adobe, Apple, Google, and Microsoft announced the technology, which allows a single font file to store a continuous range of design variants. One of the key benefits of variable fonts is that they can significantly reduce the combined size of font data whenever multiple styles are in use. † ℹ︎ v-fonts.com

Variable scope : → Scope

VBA : → Visual Basic for Applications

VDD : → Value-Driven Design

Vector image : An image defined in terms of 2D points, which are connected by lines and curves to form polygons and other shapes. Each of these points has a definite position on the x- and y-axis of the work plane and determines the direction of the path; further, each path may have various properties including values for stroke color, shape, curve, thickness, and fill. Vector graphics are commonly found today in the SVG, EPS, PDF, and AI graphic file formats and are intrinsically different from the more common raster graphics file formats such as GIF, JPEG, PNG, and MPEG4. †

Velocity : A metric for work done, which is often used in agile software development. The velocity metric is used for planning Sprints and measuring team performance, though there is no evidence that measuring velocity improves planning effectiveness or team performance. †

Vendor prefix : A marker for experimental or non-standard CSS properties and JavaScript APIs, so that developers can experiment with new ideas while—in theory—preventing their experiments from being relied upon and then breaking web developers’ code during the standardization process. Developers should wait to include unprefixed properties until browser behavior is standardized. For CSS, the major browsers use the prefixes -webkit- (Chrome, Safari, newer versions of Opera, almost all iOS browsers including Firefox for iOS; essentially, any WebKit-based browser), -moz- (Firefox), -o- (old pre-WebKit versions of Opera), and -ms- (Internet Explorer and Edge). These are similar for API prefixes. ‡

Verification : Verification is intended to check that a product, service, or system (or portion thereof) meets a set of design specifications. In the development phase, verification procedures involve performing special tests to model or simulate a portion, or the entirety, of a product, service, or system, then performing a review or analysis of the modeling results. In the post-development phase, verification procedures involve regularly repeating tests devised specifically to ensure that the product, service, or system continues to meet the initial design requirements, specifications, and regulations as time progresses. †

Version control : The management of changes to documents, computer programs, large websites, and other collections of information. Changes are usually identified by a number or letter code, termed a revision number, revision level, or just revision. Each revision is associated with a timestamp and the person making the change. Revisions can be compared, restored, and with some types of files, merged. Today, the most capable (as well as complex) version control systems are those used in software development, where a team of people may concurrently make changes to the same files. †

Versioning : The process of assigning either unique version names or unique version numbers to unique states of computer software. Within a given version number category (major, minor, patch), these numbers are generally assigned in increasing order and correspond to new developments in the software. At a fine-grained level, version control is often used for keeping track of incrementally different versions of information. Modern computer software is often tracked using two different software versioning schemes—an internal version number that may be incremented many times in a single day, such as a revision control number, and a release version that typically changes far less often. †

Vertical scaling : An increase in the capabilities of an individual resource, e.g., by equipping a machine with a faster CPU, more memory, or more disk space.

vi : A screen-oriented text editor originally created for the Unix operating system. The portable subset of the behavior of vi and programs based on it, and the ex editor language supported within these programs, is described by the Single Unix Specification and POSIX. The original code for vi was written in 1976 by Bill Joy, as the visual mode for the ex line editor. The name “vi” is derived from the shortest unambiguous abbreviation for the ex command visual, which switches the ex line editor to visual mode. †

Viewport : A polygon viewing region in computer graphics, and in browser, the visible portion of the entire document. If the document is larger than the viewport, the user can shift the viewport around by scrolling. †

Vim : A clone, with additions, of the vi text editor program for Unix. Vim is designed for use both from a command-line interface and as a standalone application in a graphical user interface. It was released in 1991 by Bram Moolenaar. † ℹ︎ vim.org

Virtual inheritance : A C++ technique that ensures only one copy of a base class’s member variables are inherited by grandchild-derived classes. Without virtual inheritance, if two classes B and C inherit from a class A, and a class D inherits from both B and C, then D will contain two copies of A’s member variables: one via B, and one via C. These will be accessible independently, using scope resolution. Instead, if classes B and C inherit virtually from class A, then objects of class D will contain only one set of the member variables from class A. This feature is most useful for multiple inheritance, as it makes the virtual base a common subobject for the deriving class and all classes that are derived from it. †

Virtual LAN : A broadcast domain that is partitioned and isolated in a computer network at the data link layer (OSI model layer 2). VLANs work by applying tags to network frames and handling these tags in networking systems, creating the appearance and functionality of network traffic that is physically on a single network but acts as if it was split between separate networks. In this way, VLANs can keep network applications separate despite being connected to the same physical network, and without requiring multiple sets of cabling and networking devices to be deployed. †

Virtual Machine : An emulation of a computer system. Virtual machines are based on computer architectures and provide functionality of a physical computer. Their implementations may involve specialized hardware, software, or a combination. There are different kinds of virtual machines, each with different functions: System virtual machines (also termed full virtualization VMs) provide a substitute for a real machine; process virtual machines, on the other hand, are designed to execute computer programs in a platform-independent environment. †

Virtual Machine Manager : → Hypervisor

Virtual Machine Monitor : → Hypervisor

Virtual Private Cloud : An on-demand configurable pool of shared computing resources allocated within a public cloud environment, providing a certain level of isolation between the different organizations using the resources. The isolation between one VPC organization and all other users of the same cloud (other VPC organizations as well as other public cloud users) is usually achieved through allocation of a private IP subnet and a virtual communication construct (such as a VLAN or a set of encrypted communication channels) per user. In a VPC, the respective isolation is accompanied with a VPN function that secures remote access of the organization to VPC resources. A VPC is most commonly used in the context of cloud Infrastructure as a Service (IaaS). †

Virtual Private Network : An extension of a private network across a public network, enabling users to send and receive data across shared or public networks as if their computing devices were directly connected to the private network. Applications running on a computing device (e.g., a desktop computer, laptop, or smartphone) across a VPN may therefore benefit from the functionality, security, and management of the private network. Encryption is a common, though not an inherent, part of a VPN connection. †

Virtual Reality : A simulated experience that can be similar to or completely different from the real world. Applications of virtual reality can include entertainment (i.e., video games) and educational purposes (i.e., medical or military training). Other, distinct types of VR style technology include augmented reality and mixed reality. Currently standard virtual reality systems use either virtual reality headsets or multi-projected environments to generate realistic images, sounds, and other sensations that simulate a user’s physical presence in a virtual environment. †

Virtualization : The act of creating a virtual (rather than actual) version of something, including virtual computer hardware platforms, storage devices, and computer network resources. Virtualization began in the 1960s, as a method of logically dividing the system resources provided by mainframe computers between different applications. Since then, the meaning of the term has broadened. †

Virtualizer : → Hypervisor

Visual Basic for Applications : An implementation of Microsoft’s event-driven programming language Visual Basic 6, which was declared legacy in 2008, and its associated integrated development environment (IDE). The VBA programming language was upgraded in 2010 with the introduction of Visual Basic for Applications 7 in Microsoft Office applications. Visual Basic for Applications enables building user-defined functions (UDFs), automating processes, and accessing Windows API and other low-level functionality through dynamic-link libraries (DLLs). It supersedes and expands on the abilities of earlier application-specific macro programming languages such as Word’s WordBASIC. VBA was first released in 1993. †

Visual formatting model : A model for how user agents take the document tree, and process and display it for visual media. This includes continuous media such as a computer screen, and paged media such as a book or document printed by browser print functions. In the visual formatting model, each element in the document tree generates zero or more boxes according to the box model. The layout of these boxes is governed by box dimensions and type, positioning scheme (normal flow, float, and absolute positioning), relationships between elements in the document tree, and external information (e.g., viewport size, intrinsic dimensions of images, etc.). ‡

Visual impairment : A decreased ability to see to a degree that causes problems not fixable by usual means, such as glasses. Some classifications also include those who have a decreased ability to see because they do not have access to glasses or contact lenses. Visual impairment is often defined as a best corrected visual acuity of worse than either 20/40 or 20/60. The term “blindness” is used for complete or nearly complete vision loss. †

Visual regression testing : Usually automated testing for unintended visual changes (regressions) on a website or app.

Visual Studio Code : A cross-platform source code editor developed by Microsoft. VS Code includes support for debugging, embedded Git control, syntax highlighting, intelligent code completion, snippets, and code refactoring. It is highly customizable, allowing users to change theme, keyboard shortcuts, and preferences, and to install extensions that add additional functionality. VS Code was first released in 2015. † ℹ︎ code.visualstudio.com

Vishing : → Voice phishing

VLAN : → Virtual LAN

VM : → Virtual Machine

VMM : → Virtual Machine Manager : → Virtual Machine Monitor

Voice over IP : A method and group of technologies for the delivery of voice communications and multimedia sessions over Internet Protocol (IP) networks. The steps and principles involved in originating VoIP telephone calls are similar to traditional digital telephony and involve signaling, channel setup, digitization of the analog voice signals, and encoding. Instead of being transmitted over a circuit-switched network, the digital information is packetized and transmission occurs as IP packets over a packet-switched network. †

Voice phishing : A form of criminal phone fraud, using social engineering over the telephone system to gain access to private personal and financial information for the purpose of financial reward. Voice phishing is sometimes referred to as “vishing,” a portmanteau of “voice” and “phishing.” †

VoiceOver : A screen reader built into Apple’s macOS, iOS, tvOS, and watchOS operating systems. By using VoiceOver, the user can access their Mac or iOS device based on spoken descriptions and, in the case of the Mac, the keyboard. The feature is designed to increase accessibility for blind and low-vision users, as well as for users with dyslexia. † ℹ︎ apple.com/accessibility/mac/vision

VoiceXML : A digital document standard for specifying interactive media and voice dialogs between humans and computers. VoiceXML is used for developing audio and voice response applications, such as banking systems and automated customer service portals. VoiceXML applications are developed and deployed in a manner analogous to how a web browser interprets and visually renders the HTML it receives from a web server. VoiceXML documents are interpreted by a voice browser and in common deployment architectures, users interact with voice browsers via the public switched telephone network (PSTN). The VoiceXML document format is based on Extensible Markup Language (XML). VoiceXML is a standard developed by the World Wide Web Consortium (W3C), whose first version was released in 1999. † ℹ︎ w3.org/TR/voicexml20

Void element : An element from HTML, SVG, or MathML that cannot have any child nodes (i.e., nested elements or text nodes). For HTML, the void elements are <area>, <base>, <br>, <col>, <embed>, <hr>, <img>, <input>, <link>, <meta>, <param>, <source>, <track>, and <wbr>. ‡

VoIP : → Voice over IP

VPC : → Virtual Private Cloud

VPN : → Virtual Private Network

VR : → Virtual Reality

VRT : → Visual regression testing

VS Code : → Visual Studio Code

Vue : → Vue.js

Vue.js : A model-view-viewmodel JavaScript framework for building user interfaces and single-page applications. Vue.js features an incrementally adoptable architecture that focuses on declarative rendering and component composition. Advanced features required for complex applications such as routing, state management, and build tooling are offered via officially maintained supporting libraries and packages, with Nuxt.js as one of the most popular solutions. Vue.js was created in 2014 by Evan You. † ℹ︎ vuejs.org

VuePress : A static site generator based on Vue.js. ℹ︎ vuepress.vuejs.org

Vuex : A state management pattern and library for Vue.js applications. ℹ︎ vuex.vuejs.org

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