Creating Learning Instance

Hi all,

Has any one tried to create a single learning instance that can read invoices with totally different formats… like invoices from different vendors…. did you use the predefined one or used defined

If yes what are the main challenges… 

When i tried using predefined ..the first issue was that there are certain fields that exist in one format and not the other E.g: Line number… Just wondering how we can make a field as optional in the learning instance...so that it can read when available and ignore when not available…?