The Enterprise Architecture Vision statement should be created while doing high level analysis of of the project scope. The vision statement should clearly define the architecture and what the project will be addressing. This includes the as-is and to-be state of the technology environment as it aligns with business goals to create value to the enterprise. The vision document should clearly demonstrate to the business sponsors what will be accomplished in this phase of the Enterprise Architecture Program.
The architecture vision is in Phase A of the TOGAF framework.