Column domains and the "(Standalone)" suffix

Hi everybody!

I’m new using Visual Paradigm (currently reviewing the Community Edition). Maybe this is a silly question but I cannot find a clue neither in the documentation product (help, manual) nor online (forums, web). So, this is my doubt:

“Columns domains” are defined through the “column specification” form. Once defined they can be used to quickly set type, ranges and another features to any column. I noticed the suffix “(Standalone)” is appended to these definitions (the domain being used is copied without this suffix). Why this distinction?

Thanks in advanced.