SAPUI5 & OData
SAPUI5 can exchange data using XML HTTP Request object to call complete datasets from the backend systems. But SAPUI5 controls are optimized to exchange data using the open data OData protocol, also known as 'The SQL of the Web'. SAP has chosen OData as the de facto standard for all SAP solutions. SAP Hana XS Engine will support OData out of the box. SAP NetWeaver Gateway will used as the OData bridge between SAP Business Suite applications and SAPUI5 applications like SAP Fiori.
So if you want to develop SAPUI5 applications, you definitely must know the OData specifications.