This principle is described by Chris Date in his book View Updating and Relational Theory - Solving the View Update Problem
The Principle of Interchangeability states that there must be no arbitrary and unnecessary distinctions between base tables and views; in other words, views should—as far as possible—“look and feel” just like base tables so far as users are concerned.
Views are subject to integrity constraints, just like base tables (We usually think of integrity constraints as applying to base tables specifically, but The Principle of Interchangeability shows this position isn’t really tenable).
In particular, views have keys and they can have foreign keys.
We must be able to update views — because if not, then that fact in itself would constitute the clearest possible violation of The Principle of Interchangeability.