Register your OCI endpoint URL (HOOK_URL) with the buyer's SAP procurement system; the system will POST to this URL with fields including USERNAME, PASSWORD, HOOK_URL, and ~OkCode.
Validate the credentials and start a session; redirect the buyer's browser into your storefront with a pre-authenticated session cookie or token in the URL.
When the buyer clicks Check Out, build an HTML form with one row per cart line using OCI field names: VENDOR, VENDORMAT, DESCRIPTION, QUANTITY, UNIT, PRICE, CURRENCY, LEADTIME, LONGTEXT_n:132, and NEWITEM-* indexed fields.
Auto-submit the form via JavaScript to the HOOK_URL parameter captured at login; include the ~OkCode=ADDI field to signal the cart transfer to the procurement system.
The procurement system displays the transferred items in the shopping cart; any validation errors are surfaced back to the user by the procurement UI without a callback to your endpoint.
Test round-trips with SAP Ariba's OCI test harness or a mock HOOK_URL endpoint that logs all posted form fields.
Known gotchas
OCI field names are case-sensitive and must use the exact uppercase names defined in the SAP OCI spec — a typo (e.g., 'Vendor' instead of 'VENDOR') will silently drop the field in older SAP systems.
Price must be a plain decimal without currency symbols; currency is passed separately in the CURRENCY field using ISO 4217 codes.
OCI does not have a built-in mechanism for order callbacks — after the buyer places the order in SAP it is transmitted to the supplier as an EDI 850 or cXML OrderRequest via a separate integration channel.
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