DSXchange

There is any Software Development Kit (SDK) available as part of Ascential, using which a developer can create his/her own plugins and connections
Whether there are plugins for SAP BW (Business Warehouse)

The document that describes the APIs for communicating with the RTI services is supplied when the RTI Services are purchased. It is called Real Time Integration Services User Guide (DS_RTI_User.pdf), and is accompanied by a technical bulletin called Text Over JMS Binding (RTI_TOJMS.pdf).

I put these first since you posted on the RTI forum.

However, your question appears to ask about other matters. Answers to those are as follows.

The manual for writing plug-in stages is called Plug-In Writer's Guide and is available for asking from Ascential. This is not a task taken on lightly; you need to be a competent C programmer to create the stage type and a competent C++ programmer to create a GUI for it. Plus have the requisite compilers, of course!

There is a plug in stage for SAP BW, it is separately purchasable (mainly to recoup the licensing fees that Ascential must pay to SAP for certification of the stage type). Ask your vendor for the "SAP Load PACK" (PACK stands for "packaged application connectivity kit").