Consider a syntax to allow authors to create a new item at the end of an array and/or reference the last item in an array. (Both are probably needed for a complete solution). This would be useful when the array length is not known (or may change). For example, mixins the add array elements but might not know the index to use (because it depends on where/how the mixin is applied).

Perhaps redefining the omitted index to mean the last item in the array would make this more feasible. Then you could do something like:

• name[+].given = "John"
• name.family = "Doe"
• name[+].given = "Jean"
• name.family = "Does"