Web2.0 started with del.icio.us, the social bookmarking service. It was followed by Flickr, the social Photo sharing service. Both services, eventually acquired by Yahoo!, started a large revolution. The new concepts that del.icio.us introduced were:
– Social: Since the bookmarked in del.icio.us are shared, whenever you add a bookmark to your del.icio.us page, you see under it who else bookmarked this URL, & what other related bookmarks he has. This in effect upgrades the individual process of bookmarking into a social practice, in which a community of people explores the web together & share their findings.
– Web-based: The 1st thing del.icio.us did was to move the local desktop activity of bookmarking, & provide as a Web-based application. This in itself brings much value, because it decouples people’s data & apps from specific hardware they have, at specific locations.
– SOA: The bookmarks a person has, in a certain category, are exposed to the Web in standard way, so that you can integrate them in other Web sites, such as your blog. The same with your Flickr photos. This is a major shift compared to Web1.0: sites do not try to do everything, but instead use services from other sites. See Thomas Friedman’s book for this simple rule: if you need some service, don’t do it yourself, but just use the provider that does it best. Take for example NetVibes, that provides you a powerful portal, that simply brings services from other Web sites.
– Tagging: a revolutionary innovation del.icio.us introduced (at least as a Web de-facto standard) let’s you provide labels to each bookmark, called Tags, that are used to group & search your bookmarks. The revolutionary part is this: tags provide semantic meaning, that semantically links different items. What’s so revolutionary: now you can view all items, from all Web2.0 sites, that relate to a certain semantic concept, together, e.g., search ICQ in Technorati (btw, del.icio.us was conceived at a forum of Technorarti’s founder Joi Itto).
– Folksonomy: del.icio.us users create their own conceptual hierarchy (taxonomy), instead of use the dictated hierarchy created by the service. The hierarchy is based on tags, which create a graph like conceptual network (2 tags that describe the same concept have a link between them). The aggregated classification work of del.icio.us users, is called: Folksonomy, & is said to be better than the Web1.0 directories.
– RSS: the content syndication standard is used in every page & item in del.icio.us, & allows you to get feeds of whatever interests you. This has huge power. For example, on my NetVibes homepage, I see a feed of bookmarks made by del.icio.us users on the subject of AI. In effect this creates a community of Web crawlers searching the Web for me, on the subject that interests me.
– REST: You can get to the data you want in del.icio.us & similar Web2.0 services by just writing the URL pointing to the item you want, instead of searching it or following a menu. How do you know the URL? The use of the simple Representational State Transfer architecture enables that.
– Simplicity: del.icio.us founder & developer, Joshua Shachter, built it for himself & for his friends. He insists, until this day, to make it dead simple. This is probably a characteristic of Web2.0 web sites, that strives to keep things simple.
– Microformats – a group that defines Web2.0 de-facto standards