Okyline Schema Language v1.1.0

Okyline is a declarative language for describing and validating JSON structures using inline constraints on field names. Schemas are valid JSON documents with real example values.

Okyline skill version : 1.6.1

⚠️ Before any schema generation

MANDATORY: Read the reference files BEFORE producing an Okyline schema:

1. references/syntax-reference.md — complete syntax of constraints
2. references/internal-references.md — $defs and $ref
3. references/conditional-directives.md — if conditional logic
4. references/expression-language.md — if $compute is necessary

Never generate a schema based solely on this SKILL.md file. The examples here are a summary, not an exhaustive reference.

$ref: minimal usage

DO NOT use $defs/$ref unless:

1. Recursion (mandatory)
2. Explicit user request

Default → everything inline in $oky.

Core Syntax

"fieldName | constraints | label": exampleValue

• fieldName: JSON field name
• constraints: Validation rules (space-separated)
• label: Optional human-readable description
• exampleValue: Determines the inferred type

If a label is present without constraints, use | |:

❌ "acheteur|Client" → "Client" parsed as constraint! ✅ "acheteur| |Client" → "Client" is the label

Minimal Schema Structure

{
  "$oky": {
    "name|@ {2,50}|User name": "Alice",
    "email|@ ~$Email~": "alice@example.com",
    "age|(18..120)": 30
  }
}

Essential Constraints

Symbol	Meaning	Example
@	Required field	"name|@": "Alice"
?	Nullable (can be null)	"middle|?": "John"
{min,max}	String length	"code|{5,10}": "ABC123"
(min..max)	Numeric range	"age|(18..65)": 30
('a','b')	Enum values	"status|('ACTIVE','INACTIVE')": "ACTIVE"
~pattern~	Regex or format	"email|~$Email~": "a@b.com"
[min,max]	Array size	"tags|[1,5]": ["eco"]
[*]	Array (no size constraint)	"items|[*]": [1, 2]
->	Element validation constraint	"tags|[*] -> {2,10}": ["eco"]
!	Unique elements	"codes|[*]!": ["A","B"]
#	Key field (for object uniqueness)	"id|#": 123
$ref	Reference to definition (type indicator, not a validation constraint)	"address|$ref": "&Address"

Contraintes numériques ouvertes

Quand une seule borne est nécessaire, utiliser les opérateurs de comparaison :

Syntaxe	Signification	Exemple
(>0)	Strictement positif	"quantity|(>0)": 5
(>=0)	Positif ou zéro	"price|(>=0)": 29.99
(<100)	Strictement < 100	"percentage|(<100)": 50
(<=100)	≤ 100	"score|(<=100)": 85

❌ Ne jamais inventer de syntaxe avec borne manquante : (0..), (..100) ✅ Utiliser les comparaisons : (>=0), (<=100)

❌ Ne jamais inventer borne manquante : (0..99999999), (-99999999..100) ✅ Utiliser les comparaisons : (>=0), (<=100)

⚠️ INVALID SYNTAX — Okyline does NOT support open ranges:

• ❌ (0..), (..100), (1..*), (0..*)
• These will cause validation errors

Taille de collection illimitée

Utiliser * pour indiquer "pas de limite" :

Syntaxe	Signification
[*]	Tableau sans contrainte de taille
[1,*]	Au moins 1 élément, pas de maximum
[~pattern~:*]	Map avec clés validées, nombre d'entrées illimité

❌ Ne jamais omettre une borne : [1,], [~pattern~:] ✅ Utiliser * explicitement : [1,*], [~pattern~:*]

Built-in Formats

Use with ~$FormatName~: $Date, $DateTime, $Time, $Email, $Uri, $Uuid, $Ipv4, $Ipv6, $Hostname

Type Inference Rules

• Type is inferred from example value (no explicit declarations)
• 42 → Integer, 3.14 → Number, "text" → String, true → Boolean
• Arrays must have at least one element for type inference
• null cannot be used as example — no type can be inferred. Use ? for nullable fields with a real example value:

❌ "middleName|?": null ✅ "middleName|?{1,50}": "Marie"

❌ "discount|?(0..100)": null ✅ "discount|?(0..100)": 15

Decimal Values Ending in .00

JSON serializers drop trailing zeros: 78.00 becomes 78. To preserve decimal precision in examples, wrap in quotes:

❌ "amount": 78.00 → Serialized as 78, type inferred as Integer ✅ "amount": "78.00" → Preserved, type inferred as Number

This only affects decimals with zero fractional parts (.00, .0). Regular decimals (45.5) and integers (10) are unaffected.

Reusable Definitions — $defs and $ref

Okyline supports internal references to promote reuse and consistency.

$defs — Definition Repository

$defs is placed at root level (alongside $oky) and contains reusable schema fragments:

{
  "$oky": {
    "person": {
      "address | $ref": "&Address",
      "contact | $ref @": "&Email"
    }
  },
  "$defs": {
    "Address": {
      "street|@ {2,100}": "12 rue du Saule",
      "city|@ {2,100}": "Lyon"
    },
    "Email|~$Email~ {5,100}": "user@example.com"
  }
}

Definitions can be objects or scalars (with constraints in the key).

Reference Syntax — &Name

References use & prefix: &Address, &Email, &Person

Property-Level Reference — field | $ref

A field uses another schema as its type:

"address | $ref @": "&Address"        // Required address
"backup | $ref ?": "&Address"         // Optional, nullable
"emails | $ref [1,5]": ["&Email"]     // Array of 1-5 emails

Structural constraints (@, ?, [min,max], !) are defined locally at each usage. Value constraints ({min,max}, (min..max), ~pattern~) are inherited from the definition.

Important: $ref vs -> for arrays

$ref and -> serve different purposes:

• $ref = type indicator (what the elements ARE) — comes BEFORE ->
• -> = validation constraints (rules elements must satisfy) — comes AFTER $ref

For arrays of referenced types, $ref is placed with the array constraint, never after ->:

// Correct syntax
"items|[*] $ref": ["&Item"]                    // Array of Item references
"items|[1,10] $ref": ["&Item"]                 // Array of 1-10 Item references  
"items|[*] $ref -> {2,50}": ["&Item"]          // With additional element constraint

// Wrong syntax - $ref must never be after ->
❌ "items|[*] -> $ref": ["&Item"]

Object-Level Reference — Inheritance

Include all fields from a base schema:

{
  "$oky": {
    "Article": {
      "$ref": "&Auditable",
      "title|@ {1,200}": "Mon article"
    }
  },
  "$defs": {
    "Auditable": {
      "createdAt|@ ~$DateTime~": "2025-01-01T00:00:00Z",
      "updatedAt|@ ~$DateTime~": "2025-01-01T00:00:00Z"
    }
  }
}

Multiple inheritance: "$ref": ["&Auditable", "&Deletable"]

Modifying Inherited Fields

Directive	Usage	Description
$remove	"$remove": ["field1", "field2"]	Exclude inherited fields
$override	"field | $override ...": value	Replace inherited definition
$keep	"$keep": ["&A.field"]	Resolve collision in multiple inheritance

$compute Context Rules

Expressions in $compute must be attached to a field using |(%ComputeName) syntax. The expression is evaluated in the context of the parent object of the annotated field.

❌ Unattached compute (never evaluated):

"$compute": { "Valid": "total == sum(items, price)" }

✅ Attached to a field:

"total|(%Valid)": 100.0

❌ Wrong context - using absolute paths in array element validation:

"lignes|[*]": [{ "montantHT|(%Check)": 500 }],
"$compute": { "Check": "lignes[*].montantHT == lignes[*].quantite * lignes[*].prix" }

✅ Correct - references are relative to parent (the current array element):

"$oky":{
   "lignes|[*]": [{ "quantite": 5, "prix": 100, "montantHT|(%Check)": 500 }]
},
"$compute": { "Check": "montantHT == quantite * prix" }

Schema Design Workflow

1. Start with {"$oky": { ... }}
2. Identify reusable structures → define in $defs
3. Write example JSON with realistic values
4. Add @ to required fields
5. Add constraints progressively: length, range, format, enums
6. Use $ref for reusable types
7. Add conditional logic if needed ($appliedIf, $requiredIf)
8. Add computed validations if needed ($compute)

Reference Files

For detailed syntax and features, consult these references:

• Constraint syntax & patterns: See references/syntax-reference.md
• Conditional directives: See references/conditional-directives.md
• Expression language ($compute): See references/expression-language.md
• Internal references ($defs, $ref): See references/internal-references.md

Quick Patterns

// Required email
"email|@ ~$Email~": "user@example.com"

// Required string 2-50 chars
"name|@ {2,50}": "Alice"

// Optional number range
"discount|(0..100)": 15

// Enum from nomenclature
"status|@ ($STATUS)": "ACTIVE"

// Array of unique strings, 1-10 items, each 2-20 chars
"tags|@ [1,10] -> {2,20}!": ["eco", "bio"]

// Required but nullable
"middleName|@ ?{1,50}": "Marie"

// Map with pattern keys
"translations|[~^[a-z]{2}$~:10]": {"en": "Hello", "fr": "Bonjour"}

// Reference to definition (required)
"address | $ref @": "&Address"

// Array of referenced type ($ref before ->, never after)
"items | $ref @ [1,100]": ["&OrderItem"]

// Array of referenced type with element constraint
"codes | $ref [1,10] -> {2,20}": ["&Code"]

// Object inheritance
"$ref": "&Auditable"

// Multiple inheritance
"$ref": ["&Auditable", "&Deletable"]

Document Metadata (Optional) - Must be generated in this order

{
  "$okylineVersion": "1.1.0",
  "$version": "1.0.0",
  "$id": "my-schema",
  "$title": "My Schema",
  "$description": "Schema description",
  "$additionalProperties": false,
  "$oky": {
    ...
  },
  "$defs": { ... },
  "$format": { "Code": "^[A-Z]{3}-\\d{4}$" },
  "$compute": { "Total": "price * quantity" },
  "$nomenclature": { "STATUS": "ACTIVE,INACTIVE" }
}


**`$id` format**: Only letters, digits, underscores and dots allowed. Pattern: `^[a-zA-Z][a-zA-Z0-9_]*(\.[a-zA-Z][a-zA-Z0-9_]*)*$`
 ❌ `"personne-vehicules"` (hyphen not allowed)
 ✅ `"personne.vehicules"` or `"personne_vehicules"`

Common Mistakes to Avoid

• Missing $oky wrapper
• Empty arrays (need at least one element)
• Confusing [1,10] (array size) with -> {1,10} (element constraint)
• Forgetting to escape backslashes in regex (\d → \\d)
• Defining $compute expressions without attaching them to fields with |(%Name)
• Using absolute paths in $compute instead of relative references to parent context
• Using $ref without the & prefix (correct: "&Address", wrong: "Address")
• Object-level $ref targeting a scalar definition (must target object schema)
• Redefining an inherited field without using $override
• Creating circular object-level references (A includes B includes A)
• Placing $defs inside $oky (must be at root level)
• Using empty brackets [] for arrays — use [*] or omit size constraint entirely
• Applying element constraints (enum, length, range) directly to array field instead of using ->: ❌ "permis|@ ('A','B','C')[]": ["B"] ✅ "permis|@ -> ('A','B','C')": ["B"] ✅ "permis|@ [1,5] -> ('A','B','C')": ["B"]
  • Using hyphens in $id — only letters, digits, underscores and dots are allowed
• Applying element constraints (enum, length, range) directly to array field instead of using ->: ❌ "permis|@ ('A','B','C')[]": ["B"] ✅ "permis|@ -> ('A','B','C')": ["B"] ✅ "permis|@ [1,5] -> ('A','B','C')": ["B"]
• Placing $ref after -> for arrays of references ($ref is a type indicator, not a validation constraint): ❌ "children|[*] -> $ref": ["&Node"] ✅ "children|[*] $ref": ["&Node"] ✅ "children|[1,10] $ref -> {2,50}": ["&Node"]
• Using open-ended range syntax (0..) or (..100) — these don't exist! ❌ "price|(0..)": 29.99 ✅ "price|(>=0)": 29.99
• Using multiple value constraint blocks (...) on the same field: ❌ "montantTTC|@ (>=0) (%LigneTTC)": 4320 ✅ "montantTTC|@ (%LigneTTC)": 4320
• Using null as an example value, even with ? Okyline needs a valid example to infer the type.: ❌ "name|? ": null ✅ "name|? ": "Charles"
• Using decimal number example terminant par .00 sans " ". ❌ "amount|? ": 800.00 ✅ "amount|? ": "800.00"

When a field uses $compute, ALL value constraints must be inside the compute expression:

  "$compute": {
    "LigneTTC": "montantTTC >= 0 && montantTTC == montantNetHT + montantTVA"
  }

⚠️ Erreurs silencieuses (pas d'erreur syntaxe, mais problème à la validation)

• Décimales en .00 → "150.00" (sinon inféré comme Integer)
• Exemple null → impossible d'inférer le type
• Tableau vide [] → impossible d'inférer le type des éléments
• "champ|Label" → "Label" interprété comme contrainte (utiliser "champ| |Label")