What is the most widely used SOA enabled application? If you work with enterprise software, like I do, names of large German software vendor or the one here locally from Redwood City or up in the North of bay area may start popping in your head. But I would say think a little bit more. Consider this, the application being talked about is used by millions of users, across operating systems, hardware platforms with so much ease that even the metaphorical grandmas can use it. The application is blogging engines like WordPress, MovableType or Blogger. All these engines have evolved in a service oriented framework without consciously keeping the SOA approach in mind. A typical engine offers the following services

RSS – RSS was the first service offered by blogging engines and was also picked up later by websites. It was a really simple idea whose time had come. It allowed content of one site to be used in other sites. All one has to do was to publish small xml file with some excerpts of the new content and links to it. These xml files or RSS feeds as they are called are later picked by various RSS readers or clients FeedDemon, NewsGator, Bloglines etc. One can also include RSS feeds of other blogs in other sites.

XMLRPC – While RSS allows the reading interface of a blog XMLRPC is publishing interface of a blog. Using this service you publish posts to a blog in particular category. There are various innovative blogging clients available that allow publishing from desktop (w:blogger, ecto) or browsers. I even hear that those lovely unix folks have developed a plugin for emacs so that they can publish from their favorite editor. Latest news is the Word 2007 supports this natively i.e. now anybody in the organization with Microsoft Office can publish to a blog directly.

Trackback and PING – These are the alert services offered by these engine. If one author has written about writings of another author they can alert the author’s blog about it. One can also ping publicly available service that something new has been published. Again this gave rise to Technorati, Pingomatic etc.

Publish by Email – While XMLRPC is the most widely used interface to publish content for blogs. There is another interface which allows to publish by sending the email. Now one can blog by sending email from crackberries. Don’t you love it.