A note is a data diagram element that contains comments or textual information but is not part of modeling language notation. You can add a note to a data diagram to provide comments, observations, or explanations about a particular diagram element. If appropriate, you can also attach a single note to multiple diagram elements. A note is displayed as a rectangle with a folded upper-right corner, and a note attachment is displayed as a dashed line that connects the note to the diagram element.
To add a note: