SAP provides various interface technology from its first release which based on RFC and later evolved to become BAPI which follow the object encapsulation principle and follow the interface contractual design pattern. For asynchronous communication pattern often IDoc is used because it is integrated into the application as SD, MM, FI, etc. These technology based on the proprietary RFC which based on the CPIC protocol implemented in the C-Kernel of the underlying SAP basis stack.
With the emerging of the internet technology, the standard HTTP protocol was introduced to the abap kernel stack and thus new programing model like ABAP-Proxy was created to support open communication with the internet and using a lightweight protocol for better performance.
This technology is used by SKYVVA component sitting inside the abap stack of the SAP ERP 6.0, S/4HANA and SAP Business All-in-One. For integrating to the SAP Business One the HANA Service Layer is used to connect with the available API. These are the technology which is used to build a smooth and seamless integration to the on-premise SAP application suite.
On the other side thinking for the future SAP has launched the last few year’s different cloud-based products such as Ariba, SuccessFactors, Hybris, etc. and released new SAP business suite version such as S/4HANA Cloud, SAP Business One Cloud, and SAP BusinessByDesign which support the cloud deployment option.