Positions and versions

Every read happens at a position and a version:

• the position (tick) is where in the story or game the read stands. A record is visible from its position on, so “what did Ana know in chapter 6” reads tick 6;
• the version (asOfVersion) is how much of the ledger is considered. Every commit gets a new version, so a read can ignore what was written later, even about earlier positions: “what did we know about chapter 6 before last week’s revision”.

Both default to the latest. A read never sees anything later on either.

A project can declare additional time axes (axis.define), such as reading order next to story order. An event may sit at a position on each axis; a read picks its axis (at: { axis: "reading", tick: 12 }). A record whose event has no position on that axis is visible to nobody there.