Siebel Data Map - If IO field empty then don't do update

Hello,

I have integration workflow where I do data map from External IO to Internal IO and after that I do Contact update.

There is one field in External IO which is not always received and if I don't have value for this field then I should not do update for Contact field with Internal IO.

I know it is possible to do this in two ways:

1) Have 2 Integration component map with source expressions. First is used if I have the field and second map is used if I don't have the field.

2) In WF check If I have the field then use it for as input argument for Data Map. If I don't have the field in message then search up the Contact and take field value from contact and send it as input argument in WF.