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Real-time Database
Real-time database has two meanings. The most common use of the term refers to a database system which uses streaming technologies to handle workloads whose state is constantly changing. This differs from traditional databases containing persistent data, mostly unaffected by time. When referring to streaming technologies, real-time processing means that a transaction is processed fast enough for the result to come back and be acted on right away. Such real-time databases are useful for assisting social media platforms in the removal of fake news, in-store surveillance cameras identifying potential shoplifters by their behavior/movements, etc. The second meaning of the term “real-time database” adheres to a stricter definition of real-time consistent with Real-time computing. Hard real-time database systems work with a real-time operating system to ensure the temporal validity of data through the enforcement of database transaction deadlines and include a mechanism (such as trans ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Database System
In computing, a database is an organized collection of data or a type of data store based on the use of a database management system (DBMS), the software that interacts with end users, applications, and the database itself to capture and analyze the data. The DBMS additionally encompasses the core facilities provided to administer the database. The sum total of the database, the DBMS and the associated applications can be referred to as a database system. Often the term "database" is also used loosely to refer to any of the DBMS, the database system or an application associated with the database. Before digital storage and retrieval of data have become widespread, index cards were used for data storage in a wide range of applications and environments: in the home to record and store recipes, shopping lists, contact information and other organizational data; in business to record presentation notes, project research and notes, and contact information; in schools as flash cards ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Concurrency Control
In information technology and computer science, especially in the fields of computer programming, operating systems, multiprocessors, and databases, concurrency control ensures that correct results for concurrent operations are generated, while getting those results as quickly as possible. Computer systems, both software and hardware, consist of modules, or components. Each component is designed to operate correctly, i.e., to obey or to meet certain consistency rules. When components that operate concurrently interact by messaging or by sharing accessed data (in memory or storage), a certain component's consistency may be violated by another component. The general area of concurrency control provides rules, methods, design methodologies, and theories to maintain the consistency of components operating concurrently while interacting, and thus the consistency and correctness of the whole system. Introducing concurrency control into a system means applying operation constraints ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Instant Messenger
Instant messaging (IM) technology is a type of synchronous computer-mediated communication involving the immediate ( real-time) transmission of messages between two or more parties over the Internet or another computer network. Originally involving simple text message exchanges, modern IM applications and services (also called "social messengers", "messaging apps", "chat apps" or "chat clients") tend to also feature the exchange of multimedia, emojis, file transfer, VoIP (voice calling), and video chat capabilities. Instant messaging systems facilitate connections between specified known users (often using a contact list also known as a "buddy list" or "friend list") or in chat rooms, and can be standalone apps or integrated into a wider social media platform, or in a website where it can, for instance, be used for conversational commerce. Originally the term "instant messaging" was distinguished from "text messaging" by being run on a computer network instead of a cellular/ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Video Conferencing
Videotelephony (also known as videoconferencing or video calling) is the use of audio signal, audio and video for simultaneous two-way communication. Today, videotelephony is widespread. There are many terms to refer to videotelephony. ''Videophones'' are standalone devices for video calling (compare Telephone). In the present day, devices like smartphones and computers are capable of video calling, reducing the demand for separate videophones. ''Videoconferencing'' implies group communication.Mulbach et al, 1995. pg. 291. Videoconferencing is used in telepresence, whose goal is to create the illusion that remote participants are in the same room. The concept of videotelephony was conceived in the late 19th century, and versions were available to the public starting in the 1930s. Early demonstrations were installed at booths in post offices and shown at various world expositions. In 1970, AT&T launched the first commercial personal videotelephone system. In addition to videoph ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
EBay
eBay Inc. ( , often stylized as ebay) is an American multinational e-commerce company based in San Jose, California, that allows users to buy or view items via retail sales through online marketplaces and websites in 190 markets worldwide. Sales occur either via online auctions or "buy it now" instant sales, and the company charges commissions to sellers upon sales. eBay was founded by Pierre Omidyar in September 1995. It has 132 million yearly active buyers worldwide and handled $73 billion in transactions in 2023, 48% of which were in the United States. In 2023, the company had a take rate (revenue as a percentage of volume) of 13.81%. The company is listed on the Nasdaq Global Select Market and is a component of the S&P 500 and formerly the Nasdaq-100. eBay can be used by individuals, companies and governments to purchase and sell almost any legal, non-controversial item. eBay's auctions use a Vickrey auction (sealed-bid) proxy bid system. Buyers and sellers may r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Data Stream
In connection-oriented communication, a data stream is the transmission of a sequence of digitally encoded signals to convey information. Typically, the transmitted symbols are grouped into a series of packets. Data streaming has become ubiquitous. Anything transmitted over the Internet is transmitted as a data stream. Using a mobile phone to have a conversation transmits the sound as a data stream. Formal definition In a formal way, a data stream is any ordered pair ( s, \Delta ) where: # s is a sequence of tuples and # \Delta is a sequence of positive real time intervals. Content Data Stream contains different sets of data, that depend on the chosen data format. * Attributes – each attribute of the data stream represents a certain type of data, e.g. segment / data point ID, timestamp, geodata. * Timestamp attribute helps to identify when an event occurred. * Subject ID is an encoded-by-algorithm ID, that has been extracted out of a cookie. * Raw Data in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Page Fault
In computing, a page fault is an exception that the memory management unit (MMU) raises when a process accesses a memory page without proper preparations. Accessing the page requires a mapping to be added to the process's virtual address space. Furthermore, the actual page contents may need to be loaded from a back-up, e.g. a disk. The MMU detects the page fault, but the operating system's kernel handles the exception by making the required page accessible in the physical memory or denying an illegal memory access. Valid page faults are common and necessary to increase the amount of memory available to programs in any operating system that uses virtual memory, such as Windows, macOS, and the Linux kernel. Types Minor page fault If the page is loaded in memory at the time the fault is generated, but is not marked in the memory management unit as being loaded in memory, then it is called a ''minor'' or ''soft'' page fault. The page fault handler in the operating system m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Memory Buffer
In computer science, a data buffer (or just buffer) is a region of memory used to store data temporarily while it is being moved from one place to another. Typically, the data is stored in a buffer as it is retrieved from an input device (such as a microphone) or just before it is sent to an output device (such as speakers); however, a buffer may be used when data is moved between processes within a computer, comparable to buffers in telecommunication. Buffers can be implemented in a fixed memory location in hardware or by using a virtual data buffer in software that points at a location in the physical memory. In all cases, the data stored in a data buffer is stored on a physical storage medium. The majority of buffers are implemented in software, which typically use RAM to store temporary data because of its much faster access time when compared with hard disk drives. Buffers are typically used when there is a difference between the rate at which data is received and the rate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Absolute Consistency
In deductive logic, a consistent theory is one that does not lead to a logical contradiction. A theory T is consistent if there is no formula \varphi such that both \varphi and its negation \lnot\varphi are elements of the set of consequences of T. Let A be a set of closed sentences (informally "axioms") and \langle A\rangle the set of closed sentences provable from A under some (specified, possibly implicitly) formal deductive system. The set of axioms A is consistent when there is no formula \varphi such that \varphi \in \langle A \rangle and \lnot \varphi \in \langle A \rangle. A ''trivial'' theory (i.e., one which proves every sentence in the language of the theory) is clearly inconsistent. Conversely, in an explosive formal system (e.g., classical or intuitionistic propositional or first-order logics) every inconsistent theory is trivial. Consistency of a theory is a syntactic notion, whose semantic counterpart is satisfiable theory, satisfiability. A theory is satisfiable ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scheduling Algorithms
In computing, scheduling is the action of assigning resources to perform tasks. The resources may be processors, network links or expansion cards. The tasks may be threads, processes or data flows. The scheduling activity is carried out by a mechanism called a scheduler. Schedulers are often designed so as to keep all computer resources busy (as in load balancing), allow multiple users to share system resources effectively, or to achieve a target quality-of-service. Scheduling is fundamental to computation itself, and an intrinsic part of the execution model of a computer system; the concept of scheduling makes it possible to have computer multitasking with a single central processing unit (CPU). Goals A scheduler may aim at one or more goals, for example: * maximizing ''throughput'' (the total amount of work completed per time unit); * minimizing '' wait time'' (time from work becoming ready until the first point it begins execution); * minimizing '' latency'' or '' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Persistence (computer Science)
In computer science, persistence refers to the characteristic of State (computer science), state of a system that outlives (persists for longer than) the Process (computing), process that created it. This is achieved in practice by storing the state as data in computer data storage. Programs have to transfer data to and from storage devices and have to provide mappings from the native Programming language, programming-language Data structure, data structures to the storage device data structures. Picture editing programs or Word processor, word processors, for example, achieve State (computer science), state persistence by saving their documents to computer file, files. Orthogonal or transparent persistence Persistence is said to be "Orthogonality#Computer science, orthogonal" or "transparent" when it is implemented as an intrinsic property of the execution environment of a program. An orthogonal persistence environment does not require any specific actions by programs running i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Database Transaction
A database transaction symbolizes a unit of work, performed within a database management system (or similar system) against a database, that is treated in a coherent and reliable way independent of other transactions. A transaction generally represents any change in a database. Transactions in a database environment have two main purposes: # To provide reliable units of work that allow correct recovery from failures and keep a database consistent even in cases of system failure. For example: when execution prematurely and unexpectedly stops (completely or partially) in which case many operations upon a database remain uncompleted, with unclear status. # To provide isolation between programs accessing a database concurrently. If this isolation is not provided, the programs' outcomes are possibly erroneous. In a database management system, a transaction is a single unit of logic or work, sometimes made up of multiple operations. Any logical calculation done in a consistent mode in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
