You can put the name as an identifier. An identifier is something unique, a name will not be unique or it shouldn't.

Why do you want to put the name as a user identifier? What you should do is, to create a reference between the user table and another table you should create an FK of type UserIdentifier, that will create the reference between tables, after that when you want to create a record that has the User FK you need to insert also the UserIdentifier to make the relationship and to identify the User.

Ps: The name should be text, not User Identifier generally speaking. But If you want to save in an attribute/variable some id, it should be the user identifier of data type User Identifier.

https://www.outsystems.com/training/courses/123/modeling-data/

https://www.outsystems.com/training/courses/126/aggregates-101/

But answering your question, the data type will be the same, but an id and a name are different things when you think about that, an ID is supposed to be unique, and a name is not unique. But still, you can still say the name, but the nomenclature is not right.

EDIT:

You will have a roles identifier instead of a user identifier that will say which role the user on the entity has in case you have also the user identifier in the table... But you already have a table for that on System where you can filter by user identifier and it will give you the roles that the user has.

Regards,

Márcio