Adjective - Having the quality of at-least-one-of-a-subset-ness

For example: let us say we have two form fields, name and surname. Both need to be filled out to complete and submit the form; we say these two fields are required.

We also have two other fields, email and phone number. At least one of them needs to be filled out to submit the form. We say these two fields are (???).

Does English have a singular adjective which expresses this quality? The only one I can think of is disjunctive because the concept is related to logical disjunction (OR). However, having consulted the Cambridge online dictionary it seems the word has a meaning closer to exclusive logical disjunction (XOR).

Solution 1:

According to Wikipedia:

In logic and mathematics, or is the truth-functional operator of (inclusive) disjunction, also known as alternation; the or of a set of operands is true if and only if one or more of its operands is true. The logical connective that represents this operator is typically written as ∨ or +. A∨B is true if A is true, or if B is true, or if both A and B are true. In logic, or by itself means the inclusive "or", distinguished from an exclusive "or", which is false when both of its arguments are true, while an [inclusive] or is true in that case. [Emphasis added.]

If you have two or more fields, at least one of which must be filled in by the user, you are dealing with logical or mathematical disjunction, i.e., inclusive disjunction, where inclusive is implicit unless stated otherwise. You would be on solid ground in characterizing these fields as disjunctive, but few would understand what you're saying. Better to simply say what is required: that a user complete at least one of the following set of two or more fields.