Note sure what the use of this API is exactly but here's the press release.
<quote>
The Blogger data API allows client applications to view and update Blogger content in the form of Google data API ("GData") feeds. Your client application can use GData to create new blog posts, edit or delete existing posts, and query for posts that match particular criteria.
</quote>

Link:
http://buzz.blogger.com/2006/08/blogger-api-update.html

Why is google going the atom way ?? what about RSS spec's ??

" there's a Feed class, which corresponds to the <atom:feed> element; it has methods for creating an entry, getting and setting the values of various sub-elements, and so on. There's also an Entry class, which corresponds to the <atom:entry> element. Not every element defined in the Google data APIs has its own class"