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?