announced two new features for some of its most popular APIs: partial response and partial update. This, according to Google, is part of the company's efforts to make the web faster. Instead of having to pull a full feed of data from Google Calendar, which usually included lots of extra information you don't really need, developers can now request a partial response that only includes relevant data. Developers can also use the new partial update feature to edit this data and send it back to the server without having to touch any of the unneeded data.Google just
As Google points out, these two new features in its APIs should allow developers to reduce the network, memory, and CPU resources needed to work with Google APIs. In Google's example, a full calendar feed contained 160 kB of data, while a partial feed only contained 8 kB - a 95% reduction (these links point to your own calendar, so your mileage may vary). These performance enhancements should be especially noticeable on mobile devices.
Partial response and partial update are now available for the YouTube Data API, the Calendar Data API and the Picasa Web Albums Data API. The Sidewiki Data API currently only supports partial response.
You can find a more detailed description of these new features here.