Data element on structure for interface

Hi all,

I'm working on the development of one interface from a non-sap system to SAP where on a first step SAP will capture a flat file into one structure "ZZZ" but I'm doubting about how to create this structure.

At first I was thinking on identifying a suitable component type/data element for each field (f.i. WAERS for currency field ZZZ-WAERS) but meanwhile I have noticed that for a similar interface the corresponding XXX structure was created using as data elements CHAR* type, where the * was the field length.

Which criteria would you choose in my case? and what will it depend on?

Thanks in advance.

Abdali