Is there any document for generic object service?

[Kim, Go Joong]

Hi! Experts,
 
There are some good functions in the generic object service like as
creating attachments, display related workflows etc.
At this time, I wonder there are some documents to explain it in detail.
For example, when I create a attachment, where is the local file saved?
Is there any function module to find related attachments for a document?
 
If somebody experienced it, I would like to know.
 
Best regards,
Gojoong Kim (Steve)