A couple of quick tests...
1. I linked a note to an element's note field and the following changes appeared in the note's record in t_object: PDATA1 --> "Element Note", PDATA2 --> the element's ID, PDATA4 --> "Yes".
2. I linked a note to an element's attribute and the following changes appeared: PDATA1 --> "Attribute", PDATA2 --> the attribute's ID, PDATA3 --> the attribute's name, PDATA4 --> "Yes".
I would assume the other types behave similarly, but investigation would be needed.
HTH,
Neil