Labels

Labels let you name rules and reference them from other rules, enabling composable policies.

If you want a reusable numeric calculation rather than a reusable boolean rule, see Computed Values.

Very Important Labels cannot have spaces in them.

Defining Labels

Add a label before the article. The label ends with a period:

AgeCheck. A **Person** passes the age check
if __age__ of **Person** is greater than or equal to 18.

Labels can use dot notation for hierarchical naming:

theory.check. A **Person** passes the theory test
if __theory_score__ of **Person** is greater than or equal to 43.

practical.check. A **Person** passes the practical test
if __practical_score__ of **Person** is greater than or equal to 40.

Referencing Labels with §

Use § (or $) to reference a labeled rule from another rule:

A **Person** passes the full test
if §theory.check passes
and §practical.check passes.

The § reference evaluates the referenced rule and uses its result as a condition.

Label Predicates

When referencing a label, you can use a predicate to describe the expected outcome:

Predicate	Example
passes	§ageCheck passes
succeeds	§theory.check succeeds
clears	§backgroundCheck clears
qualifies	§eligibility qualifies
meets requirements	§minimumAge meets requirements
satisfies	§criteria satisfies
is valid	§emailCheck is valid
is approved	§review is approved
has passed	§exam has passed
is authorized	§access is authorized
is certified	§training is certified
is permitted	§action is permitted
is satisfied	§condition is satisfied

Negated References

You can check that a labeled rule fails by using a negated predicate:

A **User** is denied if §eligibilityCheck fails.

This evaluates the referenced rule and inverts the result — if eligibilityCheck returns false, the negated reference returns true.

Negated Predicate	Example
fails	§check fails
does not pass	§check does not pass
does not succeed	§check does not succeed
does not clear	§check does not clear
does not qualify	§check does not qualify
does not satisfy	§check does not satisfy
does not meet requirements	§check does not meet requirements
is not valid	§check is not valid
is not approved	§check is not approved
has not passed	§check has not passed
is not authorized	§check is not authorized
is not certified	§check is not certified
is not permitted	§check is not permitted
is not satisfied	§check is not satisfied

You can combine not with a negated predicate for a double negation (which equals the positive check):

not §check fails

This is equivalent to §check passes.

Value References

Alongside the boolean reference (§label / $label), a labeled rule can also expose a numeric value that other rules read with @label.

Exposing a value with @@(...)

Inside a labeled rule’s body, wrap an arithmetic expression in @@(...) to mark its result as the rule’s exposed value. @@(...) occupies one side of a comparison — it contributes to the rule’s truth condition and publishes its value at the same time.

bob. A **policy** is good
if @@(9 minus 7) is equal to 2.

Here bob’s condition is 2 is equal to 2 (true), and bob’s exposed value is 2.

Reading a value with @label

From another rule, @label resolves to the exposed value and can be used anywhere a number is valid — comparisons, arithmetic, or inside math functions.

@label is a value-only reference: it does not count as “using” the labeled rule for connectivity. The labeled rule must still be reached by either a boolean label reference (§label / $label) or a selector-and-outcome reference (the **policy** is good), otherwise the parser reports multiple global rules.

Using $label:

Interactive Example

Reset

Policy Rule

A **policy** is valid
if 3 is greater than @bob
and $bob is valid.

bob. A **policy** is good
if @@(9 minus 7) is equal to 2.

A **policy** is valid if 3 is greater than @bob and $bob is valid. bob. A **policy** is good if @@(9 minus 7) is equal to 2.

Test Data (JSON)

{
  "policy": {}
}

{ "policy": {} }

Run

Using a selector-and-outcome reference:

Interactive Example

Reset

Policy Rule

A **policy** is valid
if @bob is greater than 3
and the **policy** is good.

bob. A **policy** is good
if @@(9 - 5) is greater than 2.

A **policy** is valid if @bob is greater than 3 and the **policy** is good. bob. A **policy** is good if @@(9 - 5) is greater than 2.

Test Data (JSON)

{
  "policy": {}
}

{ "policy": {} }

Run

@label participates in arithmetic:

@bob + 1 is equal to 3

And composes with math functions:

floor of (@bob / 2) is equal to 1

Using property references inside @@

The expression inside @@(...) can reference the data object just like any other arithmetic expression:

Interactive Example

Reset

Policy Rule

A **Order** is pricey
if @discount is greater than 10
and $discount is valid.

discount. A **Order** is discounted
if @@(__base__ of **Order** * 0.2) is greater than 0.

A **Order** is pricey if @discount is greater than 10 and $discount is valid. discount. A **Order** is discounted if @@(__base__ of **Order** * 0.2) is greater than 0.

Test Data (JSON)

{
  "Order": { "base": 100 }
}

{ "Order": { "base": 100 } }

Run

Errors

If a rule uses @label but the referenced rule has no @@(...) in its body, evaluation fails with:

Computed value '@label' not found in arithmetic expression

Full Example

Interactive Example

Reset

Policy Rule

AgeCheck. A **user** passes the age check
if __age__ of **user** is greater than or equal to 18.

StatusCheck. A **user** passes the status check
if __status__ of **user** is equal to "active".

A **user** is eligible
if §AgeCheck passes
and $StatusCheck passes.

AgeCheck. A **user** passes the age check if __age__ of **user** is greater than or equal to 18. StatusCheck. A **user** passes the status check if __status__ of **user** is equal to "active". A **user** is eligible if §AgeCheck passes and $StatusCheck passes.

Test Data (JSON)

{
  "user": {
      "age": 25,
      "status": "active"
  }
}

{ "user": { "age": 25, "status": "active" } }

Run

Try changing status to "suspended" — the age check will pass but the status check will fail, causing the overall rule to fail.

Rule References (without labels)

You can also reference rules by their outcome, without using labels:

A **user** passes the age check
if __age__ of **user** is greater than or equal to 18.

A **user** is eligible
if the **user** passes the age check.

This form matches the rule by its selector and outcome text.