Goods Receipt
Ariba allows posting of negative quantity in GR, however, if you are using webmethods, then the export file do not have the necessary parameters to post a '102 movement in backend SAP.
A 'mix' of positive and Negative quantity of GR i.e. GR and reject, if entered on Ariba, the GR is posted in Ariba, however, thre is no document created in backend.