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http://zh.wikipedia.org/wiki/%E4%BA%92%E8%81%94%E7%BD%91
The Internet is a worldwide, publicly accessible series of interconnected computer networks that transmit data by packet switching using the standard Internet Protocol (IP). It is a "network of networks" that consists of millions of smaller domestic, academic, business, and government networks, which together carry various information and services, such as electronic mail, online chat, file transfer, and the interlinked web pages and other resources of the World Wide Web (WWW).
History
Creation
The USSR's launch of Sputnik spurred the United States to create the Advanced Research Projects Agency, known as ARPA, in February 1958 to regain a technological lead.[1][2] ARPA created the Information Processing Technology Office (IPTO) to further the research of the Semi Automatic Ground Environment (SAGE) program, which had networked country-wide radar systems together for the first time. J. C. R. Licklider was selected to head the IPTO, and saw universal networking as a potential unifying human revolution.
Licklider moved from the Psycho-Acoustic Laboratory at Harvard University to MIT in 1950, after becoming interested in information technology. At MIT, he served on a committee that established Lincoln Laboratory and worked on the SAGE project. In 1957 he became a Vice President at BBN, where he bought the first production PDP-1 computer and conducted the first public demonstration of time-sharing.
At the IPTO, Licklider recruited Lawrence Roberts to head a project to implement a network, and Roberts based the technology on the work of Paul Baran,[citation needed] who had written an exhaustive study for the U.S. Air Force that recommended packet switching (as opposed to circuit switching) to make a network highly robust and survivable. After much work, the first two nodes of what would become the ARPANET were interconnected between UCLA and SRI International in Menlo Park, California, on October 29, 1969. The ARPANET was one of the "eve" networks of today's Internet. Following on from the demonstration that packet switching worked on the ARPANET, the British Post Office, Telenet, DATAPAC and TRANSPAC collaborated to create the first international packet-switched network service. In the UK, this was referred to as the International Packet Stream Service (IPSS), in 1978. The collection of X.25-based networks grew from Europe and the US to cover Canada, Hong Kong and Australia by 1981. The X.25 packet switching standard was developed in the CCITT (now called ITU-T) around 1976. X.25 was independent of the TCP/IP protocols that arose from the experimental work of DARPA on the ARPANET, Packet Radio Net and Packet Satellite Net during the same time period. Vinton Cerf and Robert Kahn developed the first description of the TCP protocols during 1973 and published a paper on the subject in May 1974. Use of the term "Internet" to describe a single global TCP/IP network originated in December 1974 with the publication of RFC 675, the first full specification of TCP that was written by Vinton Cerf, Yogen Dalal and Carl Sunshine, then at Stanford University. During the next nine years, work proceeded to refine the protocols and to implement them on a wide range of operating systems.
The first TCP/IP-wide area network was made operational by January 1, 1983 when all hosts on the ARPANET were switched over from the older NCP protocols to TCP/IP. In 1985, the United States' National Science Foundation (NSF) commissioned the construction of a university 56 kilobit/second network backbone using computers called "fuzzballs" by their inventor, David L. Mills. The following year, NSF sponsored the development of a higher-speed 1.5 megabit/second backbone that became the NSFNet. A key decision to use the DARPA TCP/IP protocols was made by Dennis Jennings, then in charge of the Supercomputer program at NSF.
The opening of the network to commercial interests began in 1988. The US Federal Networking Council approved the interconnection of the NSFNET to the commercial MCI Mail system in that year and the link was made in the summer of 1989. Other commercial electronic e-mail services were soon connected, including OnTyme, Telemail and Compuserve. In that same year, three commercial Internet Service Providers were created: UUNET, PSINET and CERFNET. Important, separate networks that offered gateways into, then later merged with, the Internet include Usenet and BITNET. Various other commercial and educational networks, such as Telenet, Tymnet, Compuserve and JANET were interconnected with the growing Internet. Telenet (later called Sprintnet) was a large privately funded national computer network with free dial-up access in cities throughout the U.S. that had been in operation since the 1970s. This network was eventually interconnected with the others in the 1980s as the TCP/IP protocol became increasingly popular. The ability of TCP/IP to work over virtually any pre-existing communication networks allowed for a great ease of growth, although the rapid growth of the Internet was due primarily to the availability of commercial routers from companies such as Cisco Systems, Proteon and Juniper, the availability of commercial Ethernet equipment for local-area networking and the widespread implementation of TCP/IP on the UNIX operating system.
Common uses of the Internet
E-mail
For more details on this topic, see E-mail.
The concept of sending electronic text messages between parties in a way analogous to mailing letters or memos predates the creation of the Internet. Even today it can be important to distinguish between Internet and internal e-mail systems. Internet e-mail may travel and be stored unencrypted on many other networks and machines out of both the sender's and the recipient's control. During this time it is quite possible for the content to be read and even tampered with by third parties, if anyone considers it important enough. Purely internal or intranet mail systems, where the information never leaves the corporate or organization's network, are much more secure, although in any organization there will be IT and other personnel whose job may involve monitoring, and occasionally accessing, the e-mail of other employees not addressed to them.
The World Wide Web
Many people use the terms Internet and World Wide Web (or just the Web) interchangeably, but, as discussed above, the two terms are not synonymous.
The World Wide Web is a huge set of interlinked documents, images and other resources, linked by hyperlinks and URLs. These hyperlinks and URLs allow the web servers and other machines that store originals, and cached copies, of these resources to deliver them as required using HTTP (Hypertext Transfer Protocol). HTTP is only one of the communication protocols used on the Internet.
Web services also use HTTP to allow software systems to communicate in order to share and exchange business logic and data.
Software products that can access the resources of the Web are correctly termed user agents. In normal use, web browsers, such as Internet Explorer and Firefox, access web pages and allow users to navigate from one to another via hyperlinks. Web documents may contain almost any combination of computer data including graphics, sounds, text, video, multimedia and interactive content including games, office applications and scientific demonstrations.
Through keyword-driven Internet research using search engines like Yahoo! and Google, millions of people worldwide have easy, instant access to a vast and diverse amount of online information. Compared to encyclopedias and traditional libraries, the World Wide Web has enabled a sudden and extreme decentralization of information and data.
Using the Web, it is also easier than ever before for individuals and organisations to publish ideas and information to an extremely large audience. Anyone can find ways to publish a web page or build a website for very little initial cost. Publishing and maintaining large, professional websites full of attractive, diverse and up-to-date information is still a difficult and expensive proposition, however.
Many individuals and some companies and groups use "web logs" or blogs, which are largely used as easily updatable online diaries. Some commercial organisations encourage staff to fill them with advice on their areas of specialization in the hope that visitors will be impressed by the expert knowledge and free information, and be attracted to the corporation as a result. One example of this practice is Microsoft, whose product developers publish their personal blogs in order to pique the public's interest in their work.
Collections of personal web pages published by large service providers remain popular, and have become increasingly sophisticated. Whereas operations such as Angelfire and GeoCities have existed since the early days of the Web, newer offerings from, for example, Facebook and MySpace currently have large followings. These operations often brand themselves as social network services rather than simply as web page hosts.
Advertising on popular web pages can be lucrative, and e-commerce or the sale of products and services directly via the Web continues to grow.
In the early days, web pages were usually created as sets of complete and isolated HTML text files stored on a web server. More recently, websites are more often created using content management system (CMS) or wiki software with, initially, very little content. Contributors to these systems, who may be paid staff, members of a club or other organisation or members of the public, fill underlying databases with content using editing pages designed for that purpose, while casual visitors view and read this content in its final HTML form. There may or may not be editorial, approval and security systems built into the process of taking newly entered content and making it available to the target visitors.
Social impact
The Internet has made possible entirely new forms of social interaction, activities and organizing, thanks to its basic features such as widespread usability and access.
Social networking websites such as Facebook and MySpace have created a new form of socialization and interaction. Users of these sites are able to add a wide variety of items to their personal pages, to indicate common interests, and to connect with others. It is also possible to find a large circle of existing acquaintances, especially if a site allows users to utilize their real names, and to allow communication among large existing groups of people.
Sites like meetup.com exist to allow wider announcement of groups which may exist mainly for face-to-face meetings, but which may have a variety of minor interactions over their group's site at meetup.org, or other similar sites.
Political organization and censorship
For more details on this topic, see Internet censorship.
In democratic societies, the Internet has achieved new relevance as a political tool. The presidential campaign of Howard Dean in 2004 in the United States became famous for its ability to generate donations via the Internet. Many political groups use the Internet to achieve a whole new method of organizing, in order to carry out Internet activism.
Some governments, such as those of Cuba, Iran, North Korea, Myanmar, the People's Republic of China, and Saudi Arabia, restrict what people in their countries can access on the Internet, especially political and religious content. This is accomplished through software that filters domains and content so that they may not be easily accessed or obtained without elaborate circumvention.
In Norway, Denmark, Finland and Sweden, major Internet service providers have voluntarily (possibly to avoid such an arrangement being turned into law) agreed to restrict access to sites listed by police. While this list of forbidden URLs is only supposed to contain addresses of known child pornography sites, the content of the list is secret.[citation needed]
Many countries, including the United States, have enacted laws making the possession or distribution of certain material, such as child pornography, illegal, but do not use filtering software.
There are many free and commercially available software programs with which a user can choose to block offensive websites on individual computers or networks, such as to limit a child's access to pornography or violence. See Content-control software.
Leisure activities
The Internet has been a major source of leisure since before the World Wide Web, with entertaining social experiments such as MUDs and MOOs being conducted on university servers, and humor-related Usenet groups receiving much of the main traffic. Today, many Internet forums have sections devoted to games and funny videos; short cartoons in the form of Flash movies are also popular. Over 6 million people use blogs or message boards as a means of communication and for the sharing of ideas.
The pornography and gambling industries have both taken full advantage of the World Wide Web, and often provide a significant source of advertising revenue for other websites. Although many governments have attempted to put restrictions on both industries' use of the Internet, this has generally failed to stop their widespread popularity.
One main area of leisure on the Internet is multiplayer gaming. This form of leisure creates communities, bringing people of all ages and origins to enjoy the fast-paced world of multiplayer games. These range from MMORPG to first-person shooters, from role-playing games to online gambling. This has revolutionized the way many people interact and spend their free time on the Internet.
While online gaming has been around since the 1970s, modern modes of online gaming began with services such as GameSpy and MPlayer, to which players of games would typically subscribe. Non-subscribers were limited to certain types of gameplay or certain games.
Many use the Internet to access and download music, movies and other works for their enjoyment and relaxation. As discussed above, there are paid and unpaid sources for all of these, using centralized servers and distributed peer-to-peer technologies. Discretion is needed as some of these sources take more care over the original artists' rights and over copyright laws than others.
Many use the World Wide Web to access news, weather and sports reports, to plan and book holidays and to find out more about their random ideas and casual interests.
People use chat, messaging and e-mail to make and stay in touch with friends worldwide, sometimes in the same way as some previously had pen pals. Social networking websites like MySpace, Facebook and many others like them also put and keep people in contact for their enjoyment.
The Internet has seen a growing number of Web desktops, where users can access their files, folders, and settings via the Internet.
Cyberslacking has become a serious drain on corporate resources; the average UK employee spends 57 minutes a day surfing the Web at work, according to a study by Peninsula Business Services.[9]
Complex architecture
Many computer scientists see the Internet as a "prime example of a large-scale, highly engineered, yet highly complex system".[10] The Internet is extremely heterogeneous. (For instance, data transfer rates and physical characteristics of connections vary widely.) The Internet exhibits "emergent phenomena" that depend on its large-scale organization. For example, data transfer rates exhibit temporal self-similarity. Further adding to the complexity of the Internet is the ability of more than one computer to use the Internet through only one node, thus creating the possibility for a very deep and hierarchal sub-network that can theoretically be extended infinitely (disregarding the programmatic limitations of the IPv4 protocol). However, since principles of this architecture date back to the 1960s, it might not be a solution best suited to modern needs, and thus the possibility of developing alternative structures is currently being looked into.[11]
According to a June 2007 article in Discover magazine, the combined weight of all the electrons moved within the Internet in a day is 0.2 millionths of an ounce.[12] Others have estimated this at nearer 2 ounces (50 grams).[13]
Marketing
The Internet has also become a large market for companies; some of the biggest companies today have grown by taking advantage of the efficient nature of low-cost advertising and commerce through the Internet, also known as e-commerce. It is the fastest way to spread information to a vast number of people simultaneously. The Internet has also subsequently revolutionized shopping—for example; a person can order a CD online and receive it in the mail within a couple of days, or download it directly in some cases. The Internet has also greatly facilitated personalized marketing which allows a company to market a product to a specific person or a specific group of people more so than any other advertising medium.
Examples of personalized marketing include online communities such as MySpace, Friendster, Orkut, Facebook and others which thousands of Internet users join to advertise themselves and make friends online. Many of these users are young teens and adolescents ranging from 13 to 25 years old. In turn, when they advertise themselves they advertise interests and hobbies, which online marketing companies can use as information as to what those users will purchase online, and advertise their own companies' products to those users.
A virtual world is an interactive simulated environment accessed by multiple users through an online interface. Virtual worlds are also called "digital worlds," "simulated worlds" and "MMOG's." There are many different types of virtual worlds, however there are six features all of them have in common:
1. Shared Space: the world allows many users to participate at once.
2. Graphical User Interface: the world depicts space visually, ranging in style from 2D "cartoon" imagery to more immersive 3D environments.
3. Immediacy: interaction takes place in real time.
4. Interactivity: the world allows users to alter, develop, build, or submit customized content.
5. Persistence: the world's existence continues regardless of whether individual users are logged in.
6. Socialization/Community: the world allows and encourages the formation of in-world social groups like teams, guilds, clubs, cliques, housemates, neighborhoods, etc.
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Virtual worlds have been created for many different purposes. The largest and most common type of virtual world is the "MMORPG" which stands for "Massively Multiplayer Online Role Playing Game." But virtual worlds have also been built for purposes other than gaming. The following section summarizes a few ways in which virtual worlds are currently used:
Commercial Gaming
Commercial gaming worlds tend to focus on a singular fictional theme and consistently follow formal conventions such as character-focused avatars, progression through an interactive narrative storyline, and a series of competitive events. Strongly influenced by fantasy, science fiction, and anime genres of literature and film, the majority of sizable virtual worlds in existence today are commercial gaming worlds. Examples include Everquest, Lineage 2, and World of Warcraft. While Virtual Worlds Review includes several top-quality gaming worlds on the review list, we mostly feature worlds that fall outside the traditional gaming mold. Fortunately there are many other great sites that contain comprehensive lists of commercial gaming worlds. Here are a few:
MPOGD.com
Gamespot
Gamespy
Socializing / Online Community Building
In addition to the traditional fantasy RPG worlds, there are many commercial community-focused virtual worlds that emphasize socializing rather than gaming. These worlds offer a more open-ended experience and are strongly influenced by the cultures of text-based chat rooms. Although small-scale, casual games may be incorporated into a social world, participants are not necessarily there to win or play a game, but rather to socialize with others and, in many cases, create and decorate a personal space such as a home, room, or apartment. Social worlds tend to use settings based on idealized versions of reality. Most provide some basic building tools and the ability to host activities and events that revolve around a wide variety of topics.
Education
Some virtual worlds have been created for educational purposes. In most cases, educational worlds are sponsored by academic institutions or nonprofit organizations, although some educational worlds are sponsored by corporations. Educational worlds come in a wide variety of forms, including 3D recreations of museum and gallery spaces, computer programming tutorials, virtual libraries, and meeting spaces for online university courses. Active Worlds Educational Universe is one of the oldest and largest networks of educational worlds. Adobe Atmosphere is also being used to build virtual worlds for educational purposes. A great example of a corporate-sponsored educational world is Mokitown.
Political Expression
Virtual worlds can serve as forums for political expression and debate. While real-world political issues can crop up in gaming, social, and educational worlds, there are a few cases in which completely separate virtual worlds have been built for the purpose of political debate or even experiments in various types of self-governing online communities. A great example of a virtual world with a political focus is AgoraXchange.
Military Training
Virtual world technologies are also being used in some interesting ways by the U.S. military. America's Army is being used as a tool to recruit potential soldiers, while companies like Forterra Systems are working with military groups to develop training simulations.
And this is just the beginning. As these technologies develop further over the next several years, virtual worlds will be used for all types of purposes as more people begin spending more time in them. If you're new to the "world of virtual worlds" we hope that Virtual Worlds Review will serve as a user-friendly, informative place to learn a bit about them. For those who are already familiar with virtual worlds, we hope the site will let you know about other types of worlds you may not have heard of before. In either case, welcome and enjoy the site.
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A virtual world is a computer-based simulated environment intended for its users to inhabit and interact via avatars. These avatars are usually depicted as textual, two-dimensional, or three-dimensional graphical representations, although other forms are possible[1] (auditory[2] and touch sensations for example). Some, but not all, virtual worlds allow for multiple users.
The computer accesses a computer-simulated world and presents perceptual stimuli to the user, who in turn can manipulate elements of the modeled world and thus experiences telepresence to a certain degree.[3] Such modeled worlds may appear similar to the real world or instead depict fantasy worlds. The model world may simulate rules based on the real world or some hybrid fantasy world. Example rules are gravity, topography, locomotion, real-time actions, and communication. Communication between users has ranged from text, graphical icons, visual gesture, sound, and rarely, forms using touch and balance senses.
Massively multiplayer online games commonly depict a world similar to the real world, with real world rules and real-time actions, and communication. Communication is usually textual, with real-time voice communication using VOIP also possible.[clarify]
Virtual worlds are not limited to games but, depending on the degree of immediacy presented, can encompass computer conferencing and text based chatrooms.
History
The concept of virtual worlds predates computers and could be traced in some sense to Pliny.[5] The mechanical-based 1962 Sensorama machine used the senses of vision, sound, balance, smells and touch (via wind) to simulate its world. Among the earliest virtual worlds to be implemented by computers were not games but generic virtual reality simulators, such as Ivan Sutherland's 1968 virtual reality device. This form of virtual reality is characterized by bulky headsets and other types of sensory input simulation. Contemporary virtual worlds, multi-user online virtual environments, emerged mostly independently of this virtual reality technology research, fueled instead by the gaming industry but drawing on similar inspiration.[6] While classic sensory-imitating virtual reality relies on tricking the perceptual system into experiencing an imersive environment, virtual worlds typically rely on mentally and emotionally engaging content which gives rise to an immersive experience.
The first virtual worlds presented on the Internet were communities and chat rooms, some of which evolved into MUDs and MUSHes. MUDs, short for “Multi User Dungeons,” are examples of virtual worlds that consist of virtual space inhabited by representations of data and other users [7]. Early virtual worlds were text-based, offering limited graphical representation, and often using a Command Line Interface.
Maze War (also known as The Maze Game, Maze Wars or simply Maze) was the first networked, 3D multi-user first person shooter game. Maze first brought us the concept of online players as eyeball "avatars" chasing each other around in a maze.” (http://www.digibarn.com/history/04-VCF7-MazeWar/index.html, 29th Feb). According to the website this was in 1974, it was played on Arpanet (the initial internet), however it could only be played on an Imlac, as it was specifically built for this type of computer.
Then in 1978 MUD was released, it however was not 3D, it was text-based and used a TELNET program, by following the link you will be able to play the game, and understand just how far virtual worlds have come since http://www.british-legends.com/. You can understandably argue whether or not this is a “virtual world” and that Maze War was more sophisticated (being 3D), but you must understand that MUD could be played by anyone, Maze War was computer specific. Perhaps in today’s senses it is not a true virtual world, but the idea of a virtual world in those days were different (see Neuromancer link in bibliography for more information).
Some early prototyptes were WorldsAway, a prototype interactive communities featuring a virtual world by CompuServe called Dreamscape, Cityspace, an educational networking and 3D computer graphics project for children, and The Palace, a 2-dimensional community driven virtual world. However, credit for the first online virtual world usually goes to Habitat, developed in 1987 by LucasFilm Games for the Commodore 64 computer, and running on the Quantum Link service (the precursor to America Online).[citation needed]
In 1996, the city of Helsinki, Finland with Helsinki Telephone Company (since Elisa Group) launched what was called the first online virtual 3D depiction intended to map an entire city. The Virtual Helsinki project was eventually renamed Helsinki Arena 2000 project and parts of the city in modern and historical context were rendered in 3D.[citation needed]
[edit] Virtual world concepts
One perception of virtual worlds requires an online persistent world, active and available 24 hours a day and seven days a week, to qualify as a true virtual world.[citation needed] Although this is possible with smaller virtual worlds, especially those that are not actually online, no massively multiplayer game runs all day, every day. All the online games listed above[clarify] include downtime for maintenance that is not included as time passing in the virtual world. While the interaction with other participants is done in real-time, time consistency is not always maintained in online virtual worlds. For example, EverQuest time passes faster than real-time despite using the same calendar and time units to present game time.
As virtual world is a fairly vague and inclusive term, the above can generally be divided along a spectrum ranging from:
massively multiplayer online role-playing games or MMORPGs where the user playing a specific character is a main feature of the game (World Of Warcraft for example).
massively multiplayer online real-life/rogue-like games or MMORLGs, the user can edit and alter their avatar at will, allowing them to play a more dynamic role, or multiple roles.
Some would argue that the MMO versions of RTS and FPS games are also virtual worlds if the world editors allow for open editing of the terrains if the "source file" for the terrain is shared. Emerging concepts include basing the terrain of such games on real satellite photos, such as those available through the Google Maps API or through a simple virtual geocaching of "easter eggs" on WikiMapia or similar mashups, where permitted.
[edit] Boundaries
Virtual worlds are well-known as being fantasy spaces sealed off from the real world, but more careful analysis reveals that the boundaries between the real and virtual worlds is quite porous. Participants constantly arrive and depart from the world, carrying with them their unique set of behavioral assumptions and attitudes that cannot be disentangled from their interactions in the virtual world.[8][clarify] For example, in virtual worlds which bring together players from multiple cultural backgrounds, a participant in a virtual world brings their own cultural preconceptions about those other cultures across the boundary into the world while playing. The term magic circle has been used to describe the imaginary barrier between the virtual world and the real world. The fantasy environment of the virtual world is protected from the intrusion of real life by this magic circle, but practices such as the sale of virtual items and virtual currency for real life currency challenges this separation while reinforcing the notion that objects in the virtual world have real life value. In a 2001 study by Edward Castronova, the value of the currency in the MMORPG Everquest was evaluated based on its exchange rate at USD 0.0107, making this unit of virtual currency of higher value than the Yen or the Lira.
Even though Virtual Worlds are most of the time seen as 3D Games, there are many different kinds of it: forums, blogs, wikis and chatrooms where communities born. Places which have their own world, their own rules, topics, jokes, members, etc... Each person who belongs to these kinds of communities can find like-minded people to talk to, whether this be a passion, the wish to share information about or just to meet new people and experience new things. Some users develop a double personality depending on which world they are interacting with. Depending on whether that person is in the real or virtual world can impact on the way they think and act. It is not all about video games and communities, virtual world also plays a part in the social as it can allow people to speak or share knowledge with each other. Best examples are instant messaging and visio-conferences which allow people to create their own virtual world. It can also be used to help hospitalized children (suffering from painful disease or autism for example) to create a comfortable and safe environment which can help them.
Although Virtual Worlds can be seen as a new way for people to socialize, they are said to be at the heart of a lot of anti-social behaviour. People playing video games online and more precisely, MMORPG are sometimes so addicted to the game that they cannot live without playing it. Such people are called “No Life” or Otaku and spend most of their time in their house not leaving it for days. They are often wrongly treated like insane people and also represented as dangerous when criminal cases imply links with video games. The thing is that video games played online are most of the time designed to be played for a long period of time (and even in the case of World Of Warcraft indefinitely – programmers provide updates and new things to discover regularly). People who abuse this kind of video games end up living most of their live in their bedrooms, do not develop any social life or skills: they communicate with friends mostly via the game or the internet, they create their own life on the internet with a specific name, image and charisma. The example of Second Life is totally unique because players develop communities and businesses in this game. Second Life is a game where the player has to create his/her own character with a human aspect and live a second life in a virtual world. The thing is that some people are so involved in this game (and created their “own self” in this game) that they have a double personality.
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