Nope... That would be somesite.com and anothersite.com. Basically, anothersite.com would share data with somesite.com. In other words, somesite.com would need to use data provided by anothersite.com to function properly. Nothing crazy about the data in question, just an id string.
A shared cookie would just be perfect, but it's not safe security-wise, and a bit painful to implement, is it?