Enterprise architecture (EA) is the process of translating business vision and strategy into effective enterprise change by creating, communicating and improving the key requirements, principles and models that describe the enterprise’s future state and enable its evolution (Wikipedia)
There are several models for representing an Entreprise Architecture. A simple notation for representing Entreprise Architectures is Archimate. The model is simple. It describes 3 views (Business, Applications, Technology) of 3 concepts (Information, Behavior and Structure).
The current architecture (AS-IS) and the future architecture (TO-BE) can be pictured using Archimate.
The objectives of the evolution are captured using a “motivation framework”, for example a goal tree.
You can read more about this methodology here :
http://www.appepaper.com/erra/overview-of-the-ereading-reference-architecture/erra-methodology