`$E{<name>}` is replaced by something the environment knows rather than the data: who is composing the document, on which device, at which moment, and what the session is connected to. An environment value is the one to use where a document has to state its own provenance — the date it was composed, the person who composed it, the database it came from — without that having to be asked of the user or fetched with a query. The name is written with the area in front of it, as in `$E{environment:...}`. Which names are available follows the product and the platform connected to, and the list is offered while the expression is being written, so it does not have to be known by heart. Like the other markers, an environment value used in a query is passed as a statement parameter rather than pasted into the text of the statement.