In Epicollect5 there are two distinct types of uniqueness:
Form: uniqueness is across all the entries of a form
Hierarchy: uniqueness is across all the child entries of a form (the parent entry is considered)
If your project has got a single form only, the uniqueness is always set to form. This means if you set a question like "What is your name" as unique, you cannot have the same name more than once.
If you have multiple forms, for each child form you have the option to decide if you want the answer to the question unique form wide or hierarchy wide. On a project featuring UNIVERSITY as the parent form, and DEPARTMENT as the child form, let's imagine you enter "Imperial College" as a UNIVERSITY entry and then you add DEPARTMENT entries to it, like Biology, History, Media etc.
If you would like to avoid having the same department entered more than once for a single UNIVERSITY entry, you might set the uniqueness on the DEPARTMENT name. If you set DEPARTMENT name to be unique as form though, you could enter "Biology" only once, regardless of the UNIVERSITY being Imperial College or another one, like Stanford. This would not work as "Biology" is a common department across universities in the world.
The solution is to set the uniqueness as hierarchy, to have the parent entry considered. This way the "Biology" DEPARTMENT can be entered only once but for each UNIVERSITY entry.
To set the uniqueness for a question, select the question and go to the "Advanced" tab:
The first option is the form uniqueness, the second option is the hierarchy uniqueness as described.
The uniqueness constraint is available for the following question types: