RSS also means that the web browser is not the only means one of the key lessons of the web 2.0 era k this: Hers addvalue. But only a of viewing a web page. While some RSs aggregators, such as small percentage of users will go to the trouble of adding vala yourapplicaton Bloglines, are web-based, others are desktop clients, and still via explicit means. Therefore, web 2.0 companies set induskve defauts for thers allow users of portable devices to subscribe to aggregating user dat and budding velue as a side-erect of ordnary use oft constantly updated content. appicaton. As noted above, they buld systems that get better the more people RSS is now being used to ot just notices of new blog entries, but also all kinds g quotes, weather data, and photo availability. This use is Napster, part of its fundamental architecture. actually a return to one of its roots: RSs was bon in 1997 out of the confluence of Dave Winers"Really Simple This architectural insight may also be more central to the success of open Syndication"technology, used to push out blog updates, and software than the more frequently ated appeal to volunteerism. The architecture Netscape's"Rich Site Summary", which allowed users of the internet, and the World wide Web, as wel as of open create custom Netscape home pages with regularly updated projects like Linux, Apache, and perL is such pursuing theirown data flows. Netscape lost interest, and the technology was sh"interest buld mle cive value asan by product Each of carried forward by blogging pioneer Userland, Winers projects has a small defined extension mechanisms, and an approach company. In the current crop of applications, we see, though, that lets amy well-behaved component be added by anyone, growing the outer the heritage of both parents layers of what Larry Wall, the creator of Perl refers to as"the oter words, these tednoboges demonstrat network effects, simply through th But RSS is only part of what makes a weblog different from that they have been designed an ordinary web page. Tom Coates remarks on the gnificance of the permalink demonstrates, by consistent effort It may seem like a trivial piece of functionality now, but it was as the Assodates program), it is passible to overby such an architectureon a effectively the device that turned weblogs from system that would not normally seem to possess ease-of-publishing phenomenon into a conversational mess of overlapping communities. For the first time it became relatively easy to gesture directly at a highly specific ost on someone else's site and talk about it. Discussion emerged. Chat emerged. And- as a result-friendships emerged or became more entrenched. The permalink was the first-and most successful -attempt to build In many ways, the combination of Rss and permalinks adds many of the features of NNTP, the Network News Protocol of the Usenet onto Http, the web protocol The blogospherecan be thought of as a new peer-to-peer equivalent to Usenet and bulletin-boards, the conversational watering holes of the early internet. Not only can people subscribe to each others' sites, and easily link to individual comments on a page, but also via a mechanism known as trackbacks, they can see when anyone else links to their pages, and can respond, either with reciprocal links, or by adding comments Interestingly, two-way links were the goal of early hypertext systems like Xanadu. Hypertext purists have celebrated trackbacks as a step towards two way links. But note that trackbacks are not properly two-way--rather, they are really(potentially) symmetrical one-way links that create the effect of two way links The difference may seem subtle, but in practice it is enormous. Social networking systems like Friendster, Orkut and LinkedIn, which require acknowledgment by the recipient in order to establish a connection, lack the same scalability as the web. As noted by Caterina Fake, co-founder of the Flickr photo sharing service, attention isRSS also means that the web browser is not the only means of viewing a web page. While some RSS aggregators, such as Bloglines, are web-based, others are desktop clients, and still others allow users of portable devices to subscribe to constantly updated content. RSS is now being used to push not just notices of new blog entries, but also all kinds of data updates, including stock quotes, weather data, and photo availability. This use is actually a return to one of its roots: RSS was born in 1997 out of the confluence of Dave Winer's "Really Simple Syndication" technology, used to push out blog updates, and Netscape's "Rich Site Summary", which allowed users to create custom Netscape home pages with regularly updated data flows. Netscape lost interest, and the technology was carried forward by blogging pioneer Userland, Winer's company. In the current crop of applications, we see, though, the heritage of both parents. But RSS is only part of what makes a weblog different from an ordinary web page. Tom Coates remarks on the significance of the permalink: It may seem like a trivial piece of functionality now, but it was effectively the device that turned weblogs from an ease-of-publishing phenomenon into a conversational mess of overlapping communities. For the first time it became relatively easy to gesture directly at a highly specific post on someone else's site and talk about it. Discussion emerged. Chat emerged. And - as a result - friendships emerged or became more entrenched. The permalink was the first - and most successful - attempt to build bridges between weblogs. In many ways, the combination of RSS and permalinks adds many of the features of NNTP, the Network News Protocol of the Usenet, onto HTTP, the web protocol. The "blogosphere" can be thought of as a new, peer-to-peer equivalent to Usenet and bulletin-boards, the conversational watering holes of the early internet. Not only can people subscribe to each others' sites, and easily link to individual comments on a page, but also, via a mechanism known as trackbacks, they can see when anyone else links to their pages, and can respond, either with reciprocal links, or by adding comments. Interestingly, two-way links were the goal of early hypertext systems like Xanadu. Hypertext purists have celebrated trackbacks as a step towards two way links. But note that trackbacks are not properly two-way--rather, they are really (potentially) symmetrical one-way links that create the effect of two way links. The difference may seem subtle, but in practice it is enormous. Social networking systems like Friendster, Orkut, and LinkedIn, which require acknowledgment by the recipient in order to establish a connection, lack the same scalability as the web. As noted by Caterina Fake, co-founder of the Flickr photo sharing service, attention is One of the key lessons of the Web 2.0 era is this: Users add value. But only a small percentage of users will go to the trouble of adding value to your application via explicit means. Therefore, Web 2.0 companies set inclusive defaults for aggregating user data and building value as a side-effect of ordinary use of the application. As noted above, they build systems that get better the more people use them. Mitch Kapor once noted that "architecture is politics." Participation is intrinsic to Napster, part of its fundamental architecture. This architectural insight may also be more central to the success of open source software than the more frequently cited appeal to volunteerism. The architecture of the internet, and the World Wide Web, as well as of open source software projects like Linux, Apache, and Perl, is such that users pursuing their own "selfish" interests build collective value as an automatic byproduct. Each of these projects has a small core, well-defined extension mechanisms, and an approach that lets any well-behaved component be added by anyone, growing the outer layers of what Larry Wall, the creator of Perl, refers to as "the onion." In other words, these technologies demonstrate network effects, simply through the way that they have been designed. These projects can be seen to have a natural architecture of participation. But as Amazon demonstrates, by consistent effort (as well as economic incentives such as the Associates program), it is possible to overlay such an architecture on a system that would not normally seem to possess it