Okyline Annex F Quick Reference - Virtual Fields

Version: 1.7.0 Date: May 2026 Status: Draft

Companion to the Okyline Core Language Quick Reference. Covers virtual fields ($field) - computed properties usable as triggers in conditional directives. Requires Annex C ($compute).

F - Virtual Fields (`$field`)

Virtual fields inject computed properties into an object during validation, as if they were present in the JSON data - but they are derived from existing fields, not supplied by the producer. Typical use: compute a tier, a classification, or a flag, then use it as a trigger in conditional directives ($appliedIf, $requiredIf, etc.). They require $compute (Annex C).

F.1 Syntax

{
  "$oky": {
    "order": {
      "$field discountTier": "%CalculateTier",
      "total": 1500.00,
      "$appliedIf discountTier('GOLD')": {
        "loyaltyBonus|@": 50.00
      }
    }
  },
  "$compute": {
    "CalculateTier": "total >= 1000 ? 'GOLD' : 'STANDARD'"
  }
}

↳ discountTier is computed, exists only during validation, used as condition trigger

Syntax: "$field <name>": "%<ComputeName>"

F.2 Rules

Value MUST be a %Name reference to $compute (no inline expressions)
Name must not collide with data fields or $appliedIf payload fields
Must not be used in $requiredIf/$forbiddenIf field lists (they are not data fields)
Must not be used in IfExist directives (existence doesn’t apply to computed values)
Declared at object level only, not inside $appliedIf payloads
Forward references → schema error

F.3 Chaining

Virtual fields evaluate sequentially in declaration order. Each can reference previously declared ones:

"$field subtotal": "%ComputeSubtotal",
"$field tax": "%ComputeTax",
"$field total": "%ComputeTotal"

"ComputeSubtotal": "price * quantity",
"ComputeTax": "subtotal * 0.2",
"ComputeTotal": "subtotal + tax"

↳ tax uses subtotal, total uses both. Order matters.

Evaluation order: Parse → Virtual fields (in order) → Conditional directives → Field constraints

F.4 Usage in Conditionals

Directive	Example
`$requiredIf`	`"$requiredIf tier('PREMIUM')": ["supportEmail"]`
`$requiredIfNot`	`"$requiredIfNot active(true)": ["reason"]`
`$forbiddenIf`	`"$forbiddenIf category('RESTRICTED')": ["publicUrl"]`
`$forbiddenIfNot`	`"$forbiddenIfNot enabled(true)": ["legacyMode"]`
`$appliedIf`	`"$appliedIf type('SPECIAL')": { ... }`
`$appliedIf` (switch)	`"$appliedIf tier": { "('GOLD')": {...}, "('SILVER')": {...} }`

Null test: "$requiredIf computedField(null)": ["fallback"]

F.5 Scope

Local only - visible within declaring object, not in nested objects or array elements
No inheritance - not carried through $ref inclusion (must redeclare)
No conflict - same name can be used in parent and child objects independently

F.6 `$compute` vs `$field`

	`$compute`	`$field`
Declared at	Root level	Object level
Value	Expression string	`%ComputeName` reference
Purpose	Reusable expressions	Derived values for conditions
Used via	`(%Name)` in field constraints	Name in condition triggers
Scope	Global	Local to declaring object

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