SAP HCI is designed as Integration System-as-a-Services (PAAS) which helps to integrate multiple independent systems/purposes for a company course of action. HCI can do Cloud to Cloud, Cloud to On-premise, On-premise to On-premise and Hybrid model. HCI provides Adapters (Connectivity choices) like: Cleaning soap Adapter, IDoc, HTTP, Mail, SFTP,Ariba, oData. https://s4-hana-cloud-architectur39615.blogrenanda.com/34057134/hana-cloud-integration