What is OpenSocial? Simply put, OpenSocial defines a common Application Programming Interface (API) for social applications across multiple social networking websites. In essence, you use the OpenSocial API to build hosted XML applications/documents written in HTML and JavaScript. The API lets your applications access the network’s friends and update feeds.

OpenSocial applications can be written in any HTML or text editor, or using the Google Gadgets framework. In fact, creating an OpenSocial application is a lot like creating a Google gadget.

The nice thing about the OpenSocial API is that you no longer have to develop separate applications for each social network. The API is cross-network compatible, so the apps you develop for one network should easily port to other OpenSocial networks.

There are actually four different APIs within the general OpenSocial API:

OpenSocial was developed by Google, Yahoo!, MySpace, and other popular social networks. The OpenSocial API was released on November 1, 2007, and already hundreds of OpenSocial applications are available.

OpenSocial Applications

What types of OpenSocial applications are available? Companies currently offering OpenSocial applications include the following:

• Flixster (www.flixter.com); movie reviews and ratings, shown in Figure 45.1.

• FotoFlexer (www.fotoflexer.com); online photo editor.

• iLike (www.ilike.com); music discovery and playlist sharing.

• Last.fm My Favorite Music (www.last.fm); music playlists.

• NewsGator (www.newsgator.com); RSS feed reader.

• RockYou (www.rockyou.com); photo sharing and slideshows, shown in Figure 45.2.

• Slide (www.slide.com); photo slideshows.

• TooStep BizX (www.toostep.com); virtual business card exchange.

• VirtualTourist (www.virtualtourist.com); travel guides and maps.

Figure 45.1. The Flixter application on MySpace.

Figure 45.2. The RockYou slideshow on MySpace.

If you want to develop your own OpenSocial applications, the place to start is the Google Code OpenSocial gateway (code.google.com/apis/opensocial), shown in Figure 45.3. From here, you can read the OpenSocial documentation, download the OpenSocial API, converse with other developers on the OpenSocial blog, and start developing your own OpenSocial apps.

Figure 45.3. The Google Code OpenSocial gateway.

As noted previously, OpenSocial applications are built on the Google gadget model. This means that you can develop your social apps with little or no serving costs, using the Google Gadget Editor. Naturally, you first have to register and obtain your API key/value, which then goes in all your app code. This is all explained on the Google Code site.

Before you start developing your application, you have to pick one of the compatible social networks as your code/testing base. This will be the main network for your application; this base code can then be ported to other OpenSocial sites.

At its core, a social application is an XML gadget file. The code is actually quite straightforward, as you can see in this simple example:

There are six main sections to the OpenSocial application code, as detailed in Table 45.1.

Table 45.1 OpenSocial Gadget Code

You can use any text editor or HTML editor to create this code. Alternatively, you can develop the code using the Google Gadget Editor. To run, the code must be uploaded to a website host; again, you can use the Google Gadget Editor for this.

You’ll also need an account at the social network site for which you’re writing. You can then use that site’s developer’s sandbox. Within the sandbox, you’ll need to supply the URL where the application is stored; you’re then prompted to authorize the application to access your profile, friends, activity stream, and the like. This installs the application on your page on that social networking site.