As mentioned previously, one of the most important goals of the SAP S/4HANA Cloud extensibility model is for extensions to be future proof. One important way that is accomplished is for extensions to only use a carefully curated list of artifacts and objects specifically released for cloud development. These are known as public released interfaces, which SAP guarantees will remain stable as mentioned in Unit 3 Lesson 2, Exploring the ABAP Cloud Development Model. These interfaces consist of artifacts such as local and remote APIs, along with extension points and are available at both the local ABAP Cloud platform layer as well as the SAP S/4HANA Cloud layer.
Local APIs that originate from the SAP S/4HANA Cloud layer (shown as "public extension point" & "public local API" in the figure) are available for developers to use from the SAP S/4HANA Cloud, ABAP environment in implementing key user or developer extensions. SAP BTP, ABAP environment, on the other hand, does not have access to these local APIs and must use remote APIs (shown as "public remote API" in the figure ) instead when designing and building side-by-side extensions. This distinction is driven by the need for APIs that should be platform-based versus APIs that are more product oriented.