To Retrieve the attachmentWrapper from the Collection by ID
You can also retrieve the attachmentWrapper by ID. Each attachment has a unique identifier. All attachments sent by Ariba SN have a unique ID and are set in the cXML OrderRequest. They are located in the element cXML/Request/OrderRequest/OrderRequestHeader/Comments/Attachment/URL as the string "cid: < unique attachment id >".
Use the service pub.ariba.supplier.attachment:getIDFromComment to extract the attachment ID from the Comments/Attachment record entry corresponding to the attachment you are interested in.
Invoke pub.ariba.supplier.attachment.collection:getWrapperFromCollection with the id field set to the extracted value.