Represent mandatory/recommended/optional relationships between items

Question

I've got a tree structure where the relationship between the parent and the child can be marked as either mandatory, recommended, or optional. This structure can be up to 3 levels deep. For example:

Parent 1
    Child 1-1 (Optional)
        Child 1-1-1 (Mandatory)
            (Course 1
            and
            Course 3)
            or 
            Course 5
        Child 1-1-2 (Recommended)
        Child 1-1-3 (Optional)
    Child 1-2 (Mandatory)
        Child 1-2-1 (Recommended)
        Child 1-2-2 (Recommended)
Parent 2
    Child 2-1 (Recommended)
        Child 2-1-1 (Optional)

I've got the display of the tree relationship down, but now I need to display the data in a table, similar to this:

Parent 1  Child 1-1  Child 1-1-1  Course 1
Parent 1  Child 1-1  Child 1-1-1  Course 3
Parent 1  Child 1-1  Child 1-1-1  Course 5
Parent 1  Child 1-1  Child 1-1-1
Parent 1  Child 1-1  Child 1-1-2
Parent 1  Child 1-1  Child 1-1-3
Parent 1  Child 1-2  Child 1-2-1
Parent 1  Child 1-2  Child 1-2-2
Parent 2  Child 2-1  Child 2-1-1

However I need some way to make it clear what the type of relationship is (mandatory/recommended/optional) in the table.

I was thinking icons might be the best way, because I can add them to the radio buttons where the relationship type is selected so it's consistent, but I'm not sure what kind of icons would be best.

We use Font Awesome extensively, so any examples from that project would be great.

Also, since I'm here, there's a potential fourth level, where the relationship is and/or ([this item and this one] or [that one]). They will also need to be displayed in the table, so suggestions for representing and/or relationships are appreciated as well.

Answer 1

I guess we'll all have to chip in with our ideas, but I fail to see anyone giving a 'right' answer to this.

The problem is that it is hard to associate icons with these words, without requiring users to know what the icons actually stand for (if such is the case I'd go for the last option).

You may wish to consider traffic light colours:

• Red for Mandatory
• Orange for Recommended
• Green for optional

If it's icons, you can choose something like this:

• Exclamation for Mandatory
• Star for recommended (like the star ratings on Amazon)
• Circle for optional (reassembling both the letter 'O', and a check box you may or not wish to tick

Or if the users are more of 'creative' types, I would consider the 'Take the umbrella' set:

• Bolt for Mandatory
• Cloud for Recommended
• Sun for optional

Answer 2

For simplifying and making your visual encoding system more consistent you can use the set:

Answer 3

In a table format, it might be difficult to display this (depending on the underlying implementation). However, what about icons overlaying lightweight/grayed arrows pointing to the children?

Mandatory: a lock icon Recommended: a check icon

Something like:

Parent 1 --[shrug]-> Child 1-1 --[lock]-> Child 1-1-1
Parent 2 --[check]-> Child 2-1

However, representing this in a table instead of a tree view is the red flag here: it's a tree! With a tree, I would have arrows curving down and to the right pointing from parents to children. There are a lot of things you can do with that kind of layout.