Screen typography is more than selecting a nicely legible typeface, it’s font sizes, leading, kerning, and perhaps color. Screen typography really takes on a different dimension for software interfaces that have to deal with lots of data. This is similar to what we know from typography in print design.
How do you display an empty value in a field that has not been defined yet? I was puzzling about this thing for some time now and came to the conclusion that two adjacent em dashes are right for information that can be set by a user, but has not been defined yet, whilst “not applicable” (or n/a) would be proper for a use case where you are dealing with mapping values to a table, and the property doesn’t apply to your source.
Have been doing some research today (ranging from 400 page “detail typography” books to the “Chicago Manual of Style”, as well as online “A list apart” et. al.)
I figured I actually have two use cases and needed to get clear about the definition of “does not exist”:
Use case 1: A field that can be set by a user in edit mode, but hasn’t been defined yet, and which is being displayed in read-only mode along with a label. (similar to this example with the spouse: qandasystem.info/english/which-dash-should-be-used-to-indicate-none-no-answer-or-not-applicable-closed/)
Use case 2: A pre-defined list of properties, to which you map values that need to be displayed in read-only mode. However, the pre-defined list of properties contain more properties than the table which is used to map the values (i.e. is missing some of the properties required by the pre-defined list of properties, hence there is no value).
For both use cases the display of “non-existing value” is a requirement, so it is impossible to set the fields along with their labels to invisible.
Unlike for standard text editing, there are no particular guidelines for these cases.
I came to the following conclusion: For use case 1: Display two adjacent em-dashes for missing information (deduced from several typography guidelines, where two adjacent em-dashes are used to show missing parts in a word).
For use case 2: Display “not applicable” or “n/a” to indicate that the mapped values have not all the properties of the pre-defined list of properties.