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Web 2.0, a phrase coined by O'Reilly Media in 2004•, refers to a supposed second-generation of Internet-based services — such as social networking sites, wikis, communication tools, and folksonomies — that emphasize online collaboration and sharing among users. O'Reilly Media, in collaboration with MediaLive International, used the phrase as a title for a series of conferences and since 2004 it has become a popular (though ill-defined and often criticized) buzzword amongst certain technical and marketing communities. Introduction Alluding to the version-numbers that commonly designate software upgrades, the phrase "Web 2.0" hints at an improved form of the World Wide Web, and some people have used the term for several years. In the opening talk of the first Web 2.0 conference, Tim O'Reilly and John Battelle summarized key principles they believed characterized Web 2.0 applications: Earlier users of the phrase "Web 2.0" employed it as a synonym for "semantic web," and indeed, the two concepts complement each other. The combination of social-networking systems such as FOAF and XFN with the development of tag-based folksonomies, delivered through blogs and wikis, sets up a basis for a semantic environment. Although the technologies and services that make up Web 2.0 lack the effectiveness of an internet in which the machines can understand and extract meaning (as proponents of the Semantic Web envision), Web 2.0 represents a step in its direction. As used by its proponents, the phrase "Web 2.0" refers to one or more of the following: Many find it easiest to define Web 2.0 by associating it with companies or products that embody its principles. Tim O'Reilly gave examples in his description of his "four plus one" levels in the hierarchy of Web 2.0-ness:• Examples of Web 2.0 other than those cited by O'Reilly include digg, Shoutwire, last.fm, and Technorati. • This image shows the age of some buzzwords claimed for Web 2.0 or its dependencies.">bar of Web 2.0 buzz words.'''• This image shows the age of some buzzwords claimed for Web 2.0 or its dependencies. Commentators see many recently-developed concepts and technologies as contributing to Web 2.0, including weblogs, linklogs, wikis, podcasts, RSS feeds and other forms of many-to-many publishing; social software, web APIs, web standards, online web services, and others. Proponents of the Web 2.0 concept say that it differs from early web development (retrospectively labeled Web 1.0) in that it moves away from static websites, the use of search engines, and surfing from one website to the next, towards a more dynamic and interactive World Wide Web. Others argue that later developments have not actually superseded the original and fundamental concepts of the WWW. Skeptics may see the term "Web 2.0" as little more than a buzzword; or they may suggest that it means whatever its proponents want it to mean in order to convince their customers, investors and the media that they have begun building something fundamentally new, rather than continuing to develop and use well-established technologies•. en.png|thumb|400px|On September 30, 2005, Tim O'Reilly wrote a http://www.oreillynet.com/lpt/a/6228 seminal piece neatly summarizing the subject. The mind map|mind-map pictured above (constructed by http://kosmar.de/archives/2005/11/11/the-huge-cloud-lens-bubble-map-web20/ Markus Angermeier on November 11 2005) sums up the memes of Web 2.0, with example sites and services attached. Earlier web applications or "Web 1.0" (so dubbed after the event by proponents of Web 2.0) often consisted of static HTML pages, rarely (if ever) updated. They depended solely on HTML, which a new Internet content-provider could learn fairly easily. The success of the dot-com era depended on a more dynamic Web (sometimes labeled Web 1.5) where content-management systems served dynamic HTML web-pages generated on-the-fly from a content database more amenable than raw HTML-code to change. In both senses, marketeers regarded so-called "eyeballing" as 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 has started increasingly moving towards interaction and towards rudimentary social networks, which can serve content that exploits network effects with or without creating a visual, interactive web page. In one view, Web 2.0 sites act more as points of presence, or user-dependent web portals, than as traditional websites. They have become so internally complex that new Internet users cannot create analogous websites, but remain mere users of web services provided by specialist professional experts. Access to consumer-generated content facilitated by Web 2.0 brings the web closer to Tim Berners-Lee's original concept of the web as a democratic, personal, and DIY medium of communication. Characteristics of Web 2.0 While interested parties continue to debate the definition of a Web 2.0 application, some suggest that a Web 2.0 website may exhibit some basic characteristics. These might include: The concept of web-as-participation-platform captures many of these characteristics. Bart Decrem, founder and former CEO of Flock calls Web 2.0 the "participatory web," and has argued web-as-information-source was Web 1.0. Technology overview The complex and evolving technology infrastructure of Web 2.0 includes server-software, content-syndication, messaging-protocols, standards-based browsers with plugins and extensions, and various client-applications. These differing but complementary approaches provide Web 2.0 with information-storage, creation, and dissemination capabilities that go beyond what the public formerly expected of websites. A Web 2.0 website typically features a number of the following techniques: Web-based communities Some websites that potentially sit under the Web 2.0 umbrella have built new online social networks amongst the general public. Some of the websites run social software where people work together. Other websites reproduce several individuals' RSS feeds on one page. Other ones provide deeplinking between individual websites. The syndication and messaging capabilities of Web 2.0 have fostered, to a greater or lesser degree, a tightly-woven social fabric among individuals. Arguably, the nature of online communities has changed in recent months and years. The meaning of these inferred changes, however, has pundits divided. Basically, ideological lines run thusly: Web 2.0 either empowers the individual and provides an outlet for the "voice of the voiceless"; or it elevates the amateur to the detriment of professionalism, expertise and clarity. Web-based applications and desktops The richer user-experience afforded by Ajax has prompted the development of web-sites that mimic personal computer applications, such as word processing, the spreadsheet, and slide-show presentation. WYSIWYG wiki sites replicate many features of PC authoring applications. Still other sites perform collaboration and project management functions. Java enables sites that provide computation-intensive video capability. Google, Inc. acquired one of the best-known sites of this broad class, Writely, in early 2005. Several browser-based "operating systems" or "online desktops" have also appeared. They essentially function as application platforms, not as operating systems per se. These services mimic the user experience of desktop operating-systems, offering features and applications similar to a PC environment. They have as their distinguishing characteristic the ability to run within any modern browser. Numerous web-based application services appeared during the Dot-com bubble of 1997 - 2001 and then vanished, having failed to gain a critical mass of customers. In 2005 WebEx acquired the best-known of these, Intranets.com, for slightly more than the total it had raised in venture capital after six years of trading. Rich Internet applications Recently, rich-Internet application techniques such as Ajax, Adobe Flash, Flex and OpenLaszlo have evolved that can improve the user-experience in browser-based web applications. Flash/Flex involves a web-page requesting an update for some part of its content, and altering that part in the browser, without refreshing the whole page at the same time. Server-side software The functionality of Web 2.0 rich Internet applications builds on the existing web server architecture, but puts much greater emphasis on back-end software. Syndication differs only nominally from the methods of publishing using dynamic content management, but web services typically require much more robust database and workflow support, and become very similar to the traditional intranet functionality of an application server. Vendor approaches to date fall under either a universal server approach, which bundles most of the necessary functionality in a single server platform, or a web-server plugin approach, which uses standard publishing tools enhanced with API interfaces and other tools.. Client-side software The extra functionality provided by Web 2.0 depends on the ability of users to work with the data stored on servers. This can come about through forms in an HTML page, through a scripting language such as Javascript, or through Flash or Java. These methods all make use of the client computer to reduce the server workload. RSS The first and the most important step (according to one point of view) of 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 plugin, or to a separate desktop application. Protocols which permit syndication include RSS (Really Simple Syndication — also known as web syndication), RDF (as in RSS 1.1), and Atom, all of them flavors of XML. Specialized protocols such as FOAF and XFN (both for social networking) extend functionality of sites or permit end-users to interact without centralized websites. See microformats for more specialized data formats. Due to the recent development of these trends, many of these protocols remain de facto (rather than formal) standards. Web protocols Web communication protocols provide a key element of the Web 2.0 infrastructure. Major protocols include REST and SOAP. In both cases, an API defines access to the service. Often servers use proprietary APIs, but standard web-service APIs (for example, for posting to a blog) have also come into wide use. Most (but not all) communications with web services involve some form of XML (eXtensible Markup Language). See also WSDL (Web Services Description Language) (the standard way of publishing a SOAP API) and the list of Web service specifications for links to many other web service standards, including those many whose names begin 'WS-'. Criticism Given the lack of set standards as to what "Web 2.0" actually means, implies, or requires, the term can mean radically different things to different people. For instance, many people pushing Web 2.0, talk about well-formed, validated HTML; however, not many production sites actually adhere to this standard. Many people will also talk about web sites "degrading gracefully" (designing a website so that its fundamental features remain usable by people who access it with software that does not support every technology employed by the site); however, the addition of Ajax scripting to websites can render the website completely unusable to anyone browsing with JavaScript turned off, or using a slightly older browser. Many have complained that the proliferation of Ajax scripts, in combination with unknowledgeable webmasters, has increased the instances of "tag soup": websites where coders have apparently thrown
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