Values, references, and expressions

A value expression produces a literal value, referenced value, or derived value.

Literals

JSON strings, numbers, booleans, arrays, objects, and null can be literal values.

A string beginning with @ starts a compact reference. Add a second @ to author a literal string that begins with @.

{
  "literal_email": "@@operator",
  "resolved_literal": "@operator"
}

The resolved value of "@@operator" is the literal string "@operator".

Compact references

Use @entity.member for an object, location, task, or bound collection member.

"@shipment.temperature"

A compact reference contains exactly one dot. Nested property paths are not supported.

Use @now for the current logical time. Do not add a member to @now.

Entity members

Object and location references can read built-in fields or direct properties. Task references can read supported task fields.

Task fields include start, end, duration, actor_id, status, actual_end, and progress when available.

Arithmetic

Arithmetic expressions contain one operator key.

{ "+": ["@stock.quantity", 5] }

Supported operators are +, -, *, /, min, and max. Operands must resolve to finite numbers.

Count collection members

Use count_members to count members that match an optional predicate.

{
  "count_members": {
    "collection": "available_workers",
    "as": "worker",
    "where": { "==": ["@worker.state", "available"] }
  }
}

Select a collection member

Use select_member when an expression must return one deterministic member ID.

{
  "select_member": {
    "collection": "available_workers",
    "as": "worker",
    "policy": "lowest",
    "by": "@worker.queue_length",
    "tie_break": "stable_id"
  }
}

Policies are first_by_id, lowest, and highest. The last two require by.

Declare tie_break: "stable_id" when equal ranking values are possible.

Expression locations

Canonical expression consumers include task guards, performer selection, reservations, collections, timing references, and work-definition templates.

Changes and Generator operations also evaluate expressions after source compilation. A consumer can impose a narrower type or reference requirement.

Compatibility references

Structured references remain accepted for compatibility. Do not use them for new authoring.

See compatibility-only fields and syntax for their exact forms.