Conversation so far:
what is the purpose of system vision document
A system vision document is a document that defines the high-level scope and the purpose of the system or project. This helps in reducing the risks of the system.
what components are included in a system vision document
System Vision Documents include the problem description, the anticipated business benefits, and the system capabilities.
when should a vision document be made
The Vision is created early in the Inception phase. It should evolve steadily during the earlier portion of the lifecycle, with changes slowing during Construction.

Question: are the documents similar to business cases
Self-contained rewrite: are system vision documents similar to business cases