How should we treat attributes of type `Reference`?

For some PMD files we have a different attribute type, labelled REFERENCE

Example:

  PARM REFERENCE Plant  PSRPlant

From what I've seen so far, it can be either a PARM or a VECTOR, doesn't have a dimension and isn't indexed by another attribute. Also, it points to an element from a different collection inside the study.

When we parse a PMD file, we create PSR.Attribute objects, that have the following structure:

PSRClassesInterface.jl/src/PMD/PMD.jl

Lines 17 to 24 in a6c571b

    
           struct Attribute 
        
               name::String 
        
               is_vector::Bool 
        
               type::DataType 
        
               dim::Int 
        
               index::String 
        
               # interval::String 
        
           end

From a discussion yesterday, we discovered that in other packages, this attributes stores a string that, when parsed, can lead to the element in the study.

However, we could consider some other options for PSRI, as we store the reference_id for each element in a hash table. So storing the reference_id would be more efficient.

Another alternative would be to store a tuple with the collection name and the element's index in the collection

	struct Attribute
	name::String
	is_vector::Bool
	type::DataType
	dim::Int
	index::String
	# interval::String
	end