Hi Matias,
In almost all cases the below mentioned things are considered as master data for Ariba sourcing and contracting where it is connected to the backend to ECC, and there is no material master in ariba like ECC(material basic data soted in MARA table) while creating event in sourcing system will ask you to enter discription of line item and there is no dropdown option to select other materials in ariba but if you check the attached screenshot you can identify the dropdown for commodity code
Users
Commodity Codes
Currency Conversion Rates
Units of Measure
Suppliers
Payment Terms
INCO Terms
Purchasing Units
Hope this helps you
Thanks
Kiran