Web 2.0
From Wikipedia, the free encyclopedia.
Web 2.0 is a term often applied to a perceived ongoing transition of the [URL=http://en.wikipedia.org/wiki/World_Wide_Web]World Wide Web[/URL] from a collection of [URL=http://en.wikipedia.org/wiki/Website]websites[/URL] to a full-fledged [URL=http://en.wikipedia.org/wiki/Platform_%28computing%29]computing platform[/URL] serving [URL=http://en.wikipedia.org/wiki/Web_application]web applications[/URL] to [URL=http://en.wikipedia.org/wiki/End_user]end users[/URL]. The proponents of this thinking expect that ultimately Web 2.0 services will replace [URL=http://en.wikipedia.org/wiki/Desktop_computer]desktop computing[/URL] applications for many purposes.

Contents
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[URL=http://en.wikipedia.org/wiki/Web_2.0#Overview]1 Overview[/URL]
[URL=http://en.wikipedia.org/wiki/Web_2.0#Origin_of_the_term]1.1 Origin of the term[/URL]
[URL=http://en.wikipedia.org/wiki/Web_2.0#Comparison_with_Semantic_Web]1.2 Comparison with Semantic Web[/URL]
[URL=http://en.wikipedia.org/wiki/Web_2.0#Technology]2 Technology[/URL]
[URL=http://en.wikipedia.org/wiki/Web_2.0#Content_syndication]2.1 Content syndication[/URL]
[URL=http://en.wikipedia.org/wiki/Web_2.0#Web_services]2.2 Web services[/URL]
[URL=http://en.wikipedia.org/wiki/Web_2.0#Server_software]2.3 Server software[/URL]
[URL=http://en.wikipedia.org/wiki/Web_2.0#Social_impact]3 Social impact[/URL]
[URL=http://en.wikipedia.org/wiki/Web_2.0#Business_impact]4 Business impact[/URL]
[URL=http://en.wikipedia.org/wiki/Web_2.0#External_links]5 External links[/URL]
[URL=http://en.wikipedia.org/wiki/Web_2.0#Examples]5.1 Examples[/URL]

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Overview
The original conception of the web (in this context, labelled Web 1.0) comprised static [URL=http://en.wikipedia.org/wiki/HTML]HTML[/URL] pages that were updated rarely, if at all. The success of the [URL=http://en.wikipedia.org/wiki/Dot-com]dot-com[/URL] era depended on a more dynamic web (sometimes labeled Web 1.5) where [URL=http://en.wikipedia.org/wiki/Content_management_system]content management systems[/URL] served dynamic [URL=http://en.wikipedia.org/wiki/HTML]HTML[/URL] web pages created on the fly from an ever-changing [URL=http://en.wikipedia.org/wiki/Content]content[/URL] [URL=http://en.wikipedia.org/wiki/Database]database[/URL]. In both senses, so-called eyeballing was considered intrinsic to the web experience, thus making page hits and visual aesthetics important factors.

Proponents of the Web 2.0 approach believe that web usage is increasingly oriented toward interaction and rudimentary [URL=http://en.wikipedia.org/wiki/Social_network]social networks[/URL], which can serve content that exploits [URL=http://en.wikipedia.org/wiki/Network_effect]network effects[/URL] with or without creating a visual, interactive web page. In one view, Web 2.0 sites act more as [URL=http://en.wikipedia.org/wiki/Point_of_presence]points of presence[/URL], or [URL=http://en.wikipedia.org/wiki/User_%28computing%29]user[/URL]-dependent [URL=http://en.wikipedia.org/wiki/Web_portal]web portals[/URL], than as traditional [URL=http://en.wikipedia.org/wiki/Website]websites[/URL].

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Origin of the term
The term was coined by Dale Dougherty of [URL=http://en.wikipedia.org/wiki/O%27Reilly_Media]O'Reilly Media[/URL] brainstorming with Craig Cline of MediaLive to develop ideas for a conference that they could jointly host. Dougherty suggested that the web was in a [URL=http://en.wikipedia.org/wiki/Renaissance]renaissance[/URL], with changing rules and evolving [URL=http://en.wikipedia.org/wiki/Business_model]business models[/URL]. Dougherty gave examples — "[URL=http://en.wikipedia.org/wiki/DoubleClick]DoubleClick[/URL] was Web 1.0; [URL=http://en.wikipedia.org/wiki/AdSense]Google AdSense[/URL] is Web 2.0. [URL=http://en.wikipedia.org/wiki/Ofoto]Ofoto[/URL] is Web 1.0; [URL=http://en.wikipedia.org/wiki/Flickr]Flickr[/URL] is Web 2.0." — rather than definitions, and recruited [URL=http://en.wikipedia.org/wiki/John_Battelle]John Battelle[/URL] for a business perspective, and O'Reilly Media, Battelle, and MediaLive launched the first Web 2.0 Conference in October 2004. The second annual conference will be held in October 2005.

In their conference opening talk, O'Reilly and Battelle summarized key principles they believe characterize web 2.0 applications: The web as platform; data as the "Intel Inside"; network effects driven by an "[URL=http://en.wikipedia.org/wiki/Architecture_of_participation]architecture of participation[/URL]"; innovation in assembly of systems and sites composed by pulling together features from distributed, independent developers; lightweight business models enabled by content and service syndication; the end of the software adoption cycle ("the perpetual beta"); software above the level of a single device; leveraging the power of "the [URL=http://en.wikipedia.org/wiki/Long_Tail]Long Tail[/URL]."

The use of a software-style [URL=http://en.wikipedia.org/wiki/Version#Numerical]version number[/URL] is a way of implying that the web as a whole is being rewritten and re-released as a new product with significant enhancements.

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Comparison with Semantic Web
An earlier usage of the phrase Web 2.0 was a synonym for [URL=http://en.wikipedia.org/wiki/Semantic_Web]Semantic Web[/URL]. The two concepts are similar and complementary. The combination of [URL=http://en.wikipedia.org/wiki/Social_network]social networking[/URL] systems such as [URL=http://en.wikipedia.org/wiki/FOAF]FOAF[/URL] and [URL=http://en.wikipedia.org/wiki/XFN]XFN[/URL] with the development of tag-based [URL=http://en.wikipedia.org/wiki/Folksonomy]folksonomies[/URL] and delivered through [URL=http://en.wikipedia.org/wiki/Blog]blogs[/URL] and [URL=http://en.wikipedia.org/wiki/Wiki]wikis[/URL] creates a natural basis for a semantic environment.

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Technology
The technology infrastructure of Web 2.0 is complex and evolving, but includes server software, content syndication, messaging protocols, standards-based browsers, and various client applications. (Non-standard browser plug-ins and enhancements are generally eschewed.) These differing but complementary approaches provide Web 2.0 with information storage, creation, and dissemination capabilities that go beyond what was formerly expected of websites.

A website could be said to be built using Web 2.0 technologies if it featured a number of the following techniques:

Technical:

CSS, semantically valid XHTML markup, and [URL=http://en.wikipedia.org/wiki/Microformats]Microformats[/URL]
Unobtrusive Rich Application techniques (such as [URL=http://en.wikipedia.org/wiki/Ajax_%28programming%29]Ajax[/URL])
Syndication of data in RSS/ATOM
Aggregation of RSS/ATOM data
Clean and meaningful [URL=http://en.wikipedia.org/wiki/URL]URLs[/URL]
Support posting to a weblog
RESTian (preferred) or XML Webservice APIs
Some social networking aspects (share your data with friends, etc)
General:

The site should not act as a "walled garden" - it should be easy to get data in and out of the system.
Users should own their own data on the site
Purely web based - most successful web 2.0 sites can be used almost entirely through the browser
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Content syndication
The first and most important evolution towards Web 2.0 involves the syndication of website content, using standardized protocols which permit end-users to make use of a site's data in another context, ranging from another website, to a browser plug-in, or a separate desktop application. Protocols which permit syndication include [URL=http://en.wikipedia.org/wiki/RSS_%28protocol%29]RSS[/URL], [URL=http://en.wikipedia.org/wiki/Resource_Description_Framework]RDF[/URL] (as in RSS 1.1), and [URL=http://en.wikipedia.org/wiki/Atom_%28standard%29]Atom[/URL], all of which are flavors of [URL=http://en.wikipedia.org/wiki/XML]XML[/URL]. Specialized protocols such as [URL=http://en.wikipedia.org/wiki/FOAF]FOAF[/URL] and [URL=http://en.wikipedia.org/wiki/XHTML_Friends_Network]XFN[/URL] (both for [URL=http://en.wikipedia.org/wiki/Social_network]social networking[/URL]) extend functionality of sites or permit end-users to interact without centralized websites. See [URL=http://microformats.org/]microformats[/URL] for more specialized data formats.

Due to the recent development of these trends, many of these protocols are [URL=http://en.wikipedia.org/wiki/De_facto]de facto[/URL] rather than formal standards.

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Web services
Two-way messaging protocols are one of the key elements of the Web 2.0 infrastructure. The two major types are the [URL=http://en.wikipedia.org/wiki/Representational_State_Transfer]RESTful[/URL] and [URL=http://en.wikipedia.org/wiki/Simple_Object_Access_Protocol]SOAP[/URL] methods. REST (Representational State Transfer) indicates a type of web service invocation where the client transfers the state of all transactions. SOAP (Simple Object Access Protocol) and similar lightweight methods depend on the server to retain state information. In both cases, the service is invoked through an [URL=http://en.wikipedia.org/wiki/Application_Program_Interface]Application Program Interface[/URL] (API). Often this API is customized to the website's specific needs, but standard web services APIs (for example, posting to a [URL=http://en.wikipedia.org/wiki/Blog]blog[/URL]) are also widely used. Generally the common language of web services is [URL=http://en.wikipedia.org/wiki/XML]XML[/URL] (Extensible Markup Language), but this is not guaranteed, and proprietary variations abound.

Recently, a hybrid form known as [URL=http://en.wikipedia.org/wiki/Ajax_%28programming%29]Ajax[/URL] has evolved to improve the user experience in browser-based web applications. This may be used in proprietary forms (as in [URL=http://maps.google.com/]Google Maps[/URL]) or in open form utilizing a web services API, a syndication feed, or even screen scraping.

Broadly speaking, syndication is a type of web service, but this usage is becoming less common.

See also [URL=http://en.wikipedia.org/wiki/WSDL]WSDL[/URL] (Web Services Description Language) and [URL=http://en.wikipedia.org/wiki/List_of_Web_service_specifications]List of Web service specifications[/URL] (aka WS-*).

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Server software
Web 2.0 functionality builds on the existing [URL=http://en.wikipedia.org/wiki/Web_server]web server[/URL] architecture, but puts much greater emphasis on back-end software. Syndication differs only nominally from dynamic content management publishing methods, but web services typically require much more robust [URL=http://en.wikipedia.org/wiki/Database]database[/URL] and [URL=http://en.wikipedia.org/wiki/Workflow]workflow[/URL] support, and become very similar to the traditional intranet functionality of an [URL=http://en.wikipedia.org/wiki/Application_server]application server[/URL]. Vendor approaches to date fall under either a [URL=http://en.wikipedia.org/wiki/Universal_server]universal server[/URL] approach, which bundles most of the necessary functionality in a single server platform, or a web server [URL=http://en.wikipedia.org/wiki/Plug-in]plug-in[/URL] approach, which uses standard publishing tools enhanced with API interfaces and other tools. Regardless of the approach chosen, the evolutionary path toward Web 2.0 is not expected to be significantly altered by these choices.

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Social impact
The syndication and messaging capabilities found in Web 2.0 suggest the potential to create a more tightly-woven social fabric among disparate online communities. While terms have been invented to treat these communities collectively, including [URL=http://en.wikipedia.org/wiki/Blogosphere]blogosphere[/URL] for the world of [URL=http://en.wikipedia.org/wiki/Weblogs]weblogs[/URL], [URL=http://en.wikipedia.org/wiki/Syndisphere]syndisphere[/URL] for content [URL=http://en.wikipedia.org/wiki/Syndication]syndication[/URL] feeds, and wikisphere for [URL=http://en.wikipedia.org/wiki/Wiki]wikis[/URL], other observers consider the wording and the implied value to be excessive.

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Business impact
The potential for exponential business growth as a result of the effects of Web 2.0 comes down to the difference between human-instigated value consumption and computer-instigated value consumption.

It is entirely possible for identification and consumption of value to occur without human intervention as a result of Web 2.0. Organizations will increasingly syndicate their value propositions using syndication formats such as RSS/Atom/RDF. In addition to value syndication. Web Service endpoint publishing will simplify the process of consuming the syndicated value.

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External links
[URL=http://www.web2con.com/]Web 2.0 Conference[/URL]
[URL=http://ifindkarma.typepad.com/relax/2004/10/web_20.html]Relax, Everything Is Deeply Intertwingled: Web 2.0[/URL]
[URL=http://www.kottke.org/04/10/design-for-web-20]Design for Web 2.0[/URL]
[URL=http://www.readwriteweb.com/archives/002645.php]Web 2.0 Definition and Tagging[/URL]
[URL=http://jeremy.zawodny.com/blog/archives/cat_web2.html]Jeremy Zawodny's blog: Web2 Archives[/URL]
[URL=http://www.openlinksw.com/blog/search.vspx?blogid=127&q=web+2.0&type=text&output=html]Kingsley Idehen's blog: Web2 articles[/URL]
[URL=http://groups.yahoo.com/group/van2]Vancouver Web 2.0 Forum (Van2)[/URL]
[URL=http://thinklocal.blogspot.com/2005/06/businesspersons-guide-to-web-past.html]The Businessperson's Guide to the Web: Past, Present & Future[/URL]
[URL=http://phaidon.philo.at/martin/archives/000298.html]A Cumulative Web 2.0 definition[/URL]
[URL=http://www.tbray.org/ongoing/When/200x/2005/08/04/Web-2.0]Tim Bray's comments on Web 2.0[/URL]
[URL=http://radar.oreilly.com/archives/2005/08/not_20.html]Tim O'Reilly's response to Tim Bray[/URL]
[URL=http://groups-beta.google.com/group/web2]Web 2.0 Forum[/URL]
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Examples
These companies, recognized as major "Web 1.0" successes, offer some combination of syndicated content and web services:

[URL=http://www.amazon.com/gp/browse.html/102-9325021-3580115?%5Fencoding=UTF8&node=3435361]Amazon.com Web Services[/URL]
[URL=http://www.google.com/apis/]Google Web APIs[/URL]
[URL=http://developer.yahoo.net/]Yahoo! Search Web Services[/URL]
These companies are widely thought of as Web 2.0 examples:

[URL=http://en.wikipedia.org/wiki/Flickr]Flickr[/URL]
[URL=http://del.icio.us/]del.icio.us[/URL], the shared bookmarking service that popularized [URL=http://en.wikipedia.org/wiki/Tagging]Tagging[/URL]
[URL=http://maps.google.com/]Google Maps[/URL], and more specifically, sites like [URL=http://www.housingmaps.com/]housingmaps.com[/URL] that are enabled by Google Maps

Blog——博客/网志：Blog的全名应该是Web log，后来缩写为Blog。Blog是一个易于使用的网站，您可以在其中迅速发布想法、与他人交流以及从事其他活动。所有这一切都是免费的。

RSS——站点摘要：RSS是站点用来和其他站点之间共享内容的一种简易方式（也叫聚合内容）的技术。最初源自浏览器“新闻频道”的技术，现在通常被用于新闻和其他按顺序排列的网站，例如Blog。

WIKI——百科全书：Wiki--一种多人协作的写作工具。Wiki站点可以有多人（甚至任何访问者）维护，每个人都可以发表自己的意见，或者对共同的主题进行扩展或者探讨。

Wiki指一种超文本系统。这种超文本系统支持面向社群的协作式写作，同时也包括一组支持这种写作的辅助工具。

网摘：“网摘”又名“网页书签”，起源于一家叫做Del.icio.us的美国网站自2003年开始提供的一项叫做“社会化书签”（Social Bookmarks）的网络服务，网友们称之为“美味书签”（Delicious在英文中的意思就是“美味的；有趣的”）。

SNS——社会网络：Social Network Sofwaret，社会性网络软件，依据六度理论，以认识朋友的朋友为基础，扩展自己的人脉。

P2P——对等联网：P2P是peer-to-peer的缩写，peer在英语里有“（地位、能力等）同等者”、“同事”和“伙伴”等意义。这样一来，P2P也就可以理解为“伙伴对伙伴”、“点对点”的意思，或称为对等联网。目前人们认为其在加强网络上人的交流、文件交换、分布计算等方面大有前途。

IM——即时通讯：即时通讯（Instant Messenger，简称IM）软件可以说是目前我国上网用户使用率最高的软件。聊天一直是网民们上网的主要活动之一，网上聊天的主要工具已经从初期的聊天室、论坛变为以MSN、QQ为代表的即时通讯软件。

RSS为Really Simple Syndication（简易供稿）的缩写，是某一站点用来和其它站点之间共享内容的一种简易方式，也叫聚合内容。网络用户可以在客户端借助于支持RSS的新闻聚合工具软件（例如SharpReader NewzCrawler、FeedDemon RSSReader），在不打开网站内容页面的情况下阅读支持RSS输出的网站内容。可见，网站提供RSS输出，有利于让用户发现网站内容的更新。在高速高质高效成为主流呼声的互联网时代，RSS无疑推动了网上信息的传播，提出了另一种看世界的方式。

RSS，原意是把网站内容如标题、链接、部分内文甚至全文转换为可延伸标示语言(XML：eXtensible Markup Language)的格式，以向其它网站供稿，使用者可以用一般的浏览器观看，也可以用特殊的“阅读器”软件来阅读。

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