What does a snapshot promise its reader?
Stable snapshots let observers read a particular version. Treating information as values explains why that version can be passed on without changing its meaning.
Read on through a shared source
Can today’s record explain yesterday’s decision? →Keep the value a decision actually used so that later changes do not erase its explanation.Why does shared mutable state tangle a program? →One talk separates identity from its successive values. The other shows how state couples parts of a system through time. Read them together to identify what a caller must know about earlier operations.What did the record say at the time? →Access patterns determine how to organize a store. Retaining historical facts determines which past questions it will ever be able to answer.
Compare the passages
key characteristic of a value is that it's immutablevalues are immutable right and values are semantically transparent