A node's expression engine must be one the implementation provides
The rule
Normative: this is the rule
- A node that embeds an expression selects its engine through the reserved
engineparameter, whose permitted values are exactly the engine identifiers the implementation provides. - A workflow naming an engine outside that set is refused when it is saved and again when the parameter is resolved.
- An unrecognised engine identifier that reaches evaluation by some other route fails before any expression is evaluated.
Rule identifiers are permanent and are never renumbered. Each implementation publishes its own standing against these rules; this specification does not.spec 1.0-draft · LANG-2 · changed in spec 1.0