Web 2.0 refers to websites that allow users to interact and collaborate to contribute content. Examples include social media sites, wikis and blogs. Key features of Web 2.0 sites include search functions, links between information, user authoring and tagging of content, software extensions, and notifications of content changes through RSS feeds. Technologies like Ajax allow asynchronous updating of pages for improved performance.

1. Web 2.0 The term "Web 2.0" is commonly associated with web applications that facilitate interactive information sharing, interoperability, user-centered design, and collaboration on the World Wide Web. A Web 2.0 site allows its users to interact with each other as contributors to the website's content, in contrast to websites where users are limited to the passive viewing of information that is provided to them. Examples of Web 2.0 include web-based communities, hosted services, web applications, social-networking sites, video-sharing sites, wikis, blogs, mashups, and folksonomies.

2. Technology overview Web 2.0 websites typically include some of the following features and techniques. Andrew McAfee used the acronym SLATES to refer to them Search Finding information through keyword search. Links Connects information together into a meaningful information ecosystem using the model of the Web, and provides low-barrier social tools. Authoring The ability to create and update content leads to the collaborative work of many rather than just a few web authors. In wikis, users may extend, undo and redo each other's work. In blogs, posts and the comments of individuals build up over time. Tags Categorization of content by users adding "tags" - short, usually one-word descriptions - to facilitate searching, without dependence on pre-made categories. Collections of tags created by many users within a single system may be referred to as "folksonomies" (i.e., folk taxonomies). Extensions Software that makes the Web an application platform as well as a document server. Signals The use of syndication technology such as RSS to notify users of content changes.

3. How web 2.0 works The client-side/web browser technologies typically used in Web 2.0 development are Asynchronous JavaScript and XML (Ajax), Adobe Flash and the Adobe Flex framework, and JavaScript/Ajax frameworks such as Yahoo! UI Library, Dojo Toolkit, MooTools, and jQuery. Ajax programming uses JavaScript to upload and download new data from the web server without undergoing a full page reload. To permit the user to continue to interact with the page, communications such as data requests going to the server are separated from data coming back to the page (asynchronously). Otherwise, the user would have to routinely wait for the data to come back before they can do anything else on that page, just as a user has to wait for a page to complete the reload. This also increases overall performance of the site, as the sending of requests can complete quicker independent of blocking and queueing required to send data back to the client.

5. TAXONOMY The science of categorization, or classification, of things based on a predetermined system. In reference to Web sites and portals, a site’s taxonomy is the way it organizes its data into categories and subcategories, sometimes displayed in a site map.

6. A folksonomy is a system of classification derived from the practice and method of collaboratively creating and managing tags to annotate and categorize content; this practice is also known as collaborative tagging, social classification, social indexing, and social tagging. Folksonomy, a term coined by Thomas Vander Wal, is a portmanteau of folk and taxonomy. Folksonomies became popular on the Web around 2004 as part of social software applications such as social bookmarking and photograph annotation. Tagging, which is one of the defining characteristics of Web 2.0 services, allows users to collectively classify and find information. Some websites include tag clouds as a way to visualize tags in a folksonomy. An empirical analysis of the complex dynamics of tagging systems, published in 2007, has shown that consensus around stable distributions and shared vocabularies does emerge, even in the absence of a central controlled vocabulary. Folksonomy

7. WYSIWYG WYSIWYG), is an acronym for What You See Is What You Get. The term is used in computing to describe a system in which content displayed during editing appears very similar to the final output, which might be a printed document, web page, slide presentation or even the lighting for a theatrical event.

8. WYSIWYG implies a user interface that allows the user to view something very similar to the end result while the document is being created. In general WYSIWYG implies the ability to directly manipulate the layout of a document without having to type or remember names of layout commands. The actual meaning depends on the user's perspective, e.g. * In Presentation programs, Compound documents and web pages, WYSIWYG means the display precisely represents the appearance of the page displayed to the end-user, but does not necessarily reflect how the page will be printed unless the printer is specifically matched to the editing program, as it was with the Xerox Star and early versions of the Apple Macintosh. * In Word Processing and Desktop Publishing applications, WYSIWYG means the display simulates the appearance and precisely represents the effect of fonts and line breaks on the final pagination using a specific printer configuration, so that a citation on page 1 of a 500-page document can accurately refer to a reference three hundred pages later. * WYSIWYG also describes ways to manipulate 3D models in Stereochemistry, Computer-aided design, 3D computer graphics and is the brand name of Cast Software's lighting design tool used in the theatre industry for pre-visualisation of shows.

9. RSS RSS is Really Simple Indication it is the family of web feed formats used to publish frequently updated works such as blog enteries , news headlines,audios and videos etc.RSS feeds can be read using software called an "RSS reader", "feed reader", or "aggregator", which can be web-based, desktop-based, or mobile-device-based. A standardized XML file format allows the information to be published once and viewed by many different programs.

10. TAG (META DATA) a TAG is a non-hierarchical keyword or term assigned to a piece of information (such as an internet bookmark, digital image, or computer file). This kind of metadata helps describe an item and allows it to be found again by browsing or searching. Tags are generally chosen informally and personally by the item's creator or by its viewer, depending on the system. Tagging was popularized by websites associated with Web 2.0 and is an important feature of many Web 2.0 services. It is now also part of some desktop software.

11. ATOM The name Atom applies to a pair of related standards. The Atom Syndication Format is an XML language used for web feeds, while the Atom Publishing Protocol (AtomPub or APP) is a simple HTTP-based protocol for creating and updating web resources. The Atom format was developed as an alternative to RSS

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