My client has the requirement to connect to Ariba. I know softwareAG has an Ariba OnRamp adapter. I read through the release notes and documentation. In the documentation, webMethods has the capability to handle the cXML OrderRequest with attachments, but missing in the documentation is the handling of attachments on the cXML InvoiceDetailRequest.
My requirement is to attach file images to the InvoiceDetailRequest. Does this capability exist in the adapter?
Thanks for your help 
Cannot answer your question directly, but problems many years ago with an old version of the Ariba OnRamp caused me to ditch it and write similar functionality in Flow.
If what you are doing is delivering an InvoiceDetailRequest cXML document to Ariba, you could always write a custom delivery TN service. (I’m assuming you’re using TN). Just use the Wm MIME services (pub.mime:*) to built a multipart MIME message and submit that to Ariba.
From the Ariba user guide:
Attachment Transmission
The cXML protocol supports attachment of external files through MIME. For
example, buyers often need to clarify purchase orders with supporting memos,
drawings, or faxes. Procurement applications can attach files of any type to
OrderRequest documents by using MIME. The XML document contains only
references to external MIME parts sent within one multipart MIME envelope.
When sending an OrderRequest that references external files, the referenced files can
either reside on a server accessible by the supplier, or they can be transmitted along
with the cXML document. This second option requires the use of a multipart MIME
envelope. One cXML requirement for this envelope (over the basics described in
RFC 2046 “Multipurpose Internet Mail Extensions Part Two: Media Types”) is the
inclusion of Content-ID headers with each attached file.
The following example shows the required skeleton of a cXML document with an
attached JPEG image (without the HTTP headers shown above):
POST /cXML HTTP/1.0
Content-type: multipart/mixed; boundary=something unique
--something unique
Content-type: text/xml; charset="UTF-8"
<?xml version="1.0" encoding="UTF-8"?>
…
--something unique
Content-type: image/jpeg
Content-ID: <uniqueCID@cxml.org>
…
--something unique--