US Core Data for Interoperability implementation

Hello Everyone , Good Day ! I have a question regarding the implementation of USCDI (US Core Data for Interoperability).

Why USCDI was introduced? What is the disadvantage of previous process ( communication between systems using concept like HL7) ? What is the impact of implementing this concept in existing systems ? Do we have to change logics for processing the messages? Will it effect the existing work flow of all the healthcare application?