Defs & Rules

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Defs and Rules enable conditional behavior and validation in forms and bundles.

• Defs define typed computed values that can be referenced in field/annex conditions (visible, required)
• Rules define form-level validation constraints evaluated at fill time

DefsSection

A mapping of named typed expressions keyed by camelCase identifier.

Each entry specifies a type and value. For scalar types the value is a string expression; for composite types (money, address, etc.) the value is an object with component expressions, in the same shape as the matching field value. A bbox value has southWest and northEast corners, each with lat and lon expressions.

The keys fields and parties are reserved for the context roots, and item and parent for list row references. A def with one of these keys fails validation.

RulesSection

A mapping of form-level validation rules keyed by camelCase identifier. Rules are evaluated at fill time.

CondExpr

A conditional expression used in include, required, and visible fields.

type CondExpr = boolean | string

When a string is provided, it can reference:

• Named defs from the defs section
• Field values using fields.<fieldName> (composite parts as fields.<fieldName>.<part>, e.g. fields.rent.amount)
• Inside a list item, the current row as item and, in a nested list, the enclosing row as parent (e.g. item.kind == 'other')
• Comparison operators (==, !=, >, <, >=, <=)
• Logical operators (and, or, not)
• Membership operators (in, not in)

Validation rules (rules) may also reference field values unprefixed (e.g. creditScore). See Logic for the full expression language.

Examples

$schema: https://schema.paradoc.dev/2026-10-02.json
kind: form
name: loan-application
defs:
  isEmployed:
    type: boolean
    value: "fields.employmentStatus == 'employed'"
  needsCoSigner:
    type: boolean
    value: "fields.creditScore < 650"
  showIncomeFields:
    type: boolean
    value: "isEmployed"

rules:
  creditScoreRange:
    expr: "creditScore >= 300 and creditScore <= 850"
    message: "Credit score must be between 300 and 850"
  incomeRequired:
    expr: "not isEmployed or monthlyIncome.amount > 0"
    message: "Monthly income is required for employed applicants"
    severity: error

fields:
  employmentStatus:
    type: enum
    label: Employment Status
    enum: [{ value: "employed" }, { value: "self-employed" }, { value: "unemployed" }, { value: "retired" }]

  creditScore:
    type: number
    label: Credit Score
    min: 300
    max: 850

  employer:
    type: text
    label: Employer Name
    visible: showIncomeFields
    required: showIncomeFields

  monthlyIncome:
    type: money
    label: Monthly Income
    visible: showIncomeFields
    required: showIncomeFields

  coSignerName:
    type: person
    label: Co-Signer
    visible: needsCoSigner
    required: needsCoSigner

Related

• Form - Interactive form artifact
• Bundle - Container artifact with conditional inclusion
• FormField - Field definitions with conditional properties
• FormAnnex - Attachment slots with conditional visibility and requirements