Rule Syntax & JSON Schemas

Helix rules are defined as standard JSON documents containing 4 top-level attributes: name, version, expression, and inputSchema.

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JSON Rule Structure

{
  "name": "DiscountEligibilityRule",
  "version": "1.2.0",
  "expression": "cartTotal >= 100.0 && (isMember == true || couponsApplied > 0)",
  "inputSchema": {
    "cartTotal": "double",
    "isMember": "boolean",
    "couponsApplied": "int"
  }
}

Attribute Specifications

Field	Type	Description
name	String	Unique identifier for the rule. Used for caching and ClassLoader mapping.
version	String	Semantic version string (major.minor.patch). Enables versioned caching and hot reloads.
expression	String	Infix boolean expression evaluated at runtime against the input context.
inputSchema	Object	Map of variable names to their expected primitive or object Java types.

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Supported Data Types

Schema Type Name	JVM Java Type	Default Value	Example Literals
"int"	int / java.lang.Integer	0	42, -10, 1000
"long"	long / java.lang.Long	0L	5000000000L
"double"	double / java.lang.Double	0.0	3.14159, 100.0
"boolean"	boolean / java.lang.Boolean	false	true, false
"String"	java.lang.String	null	"US", "ACTIVE", "GOLD"

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Supported Operators

Relational Operators

• Greater than: >, >=
• Less than: <, <=
• Equality: ==, !=

Logical Operators

• Logical AND: &&
• Logical OR: ||
• Logical NOT: !
• Parentheses for grouping: ( )

Arithmetic Operators

• Addition & Subtraction: +, -
• Multiplication & Division: *, /
• Modulo: %

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Context Evaluation Data Format

When evaluating a rule, provide matching key-value pairs matching the inputSchema:

examples/rules/context.json

{
  "cartTotal": 125.50,
  "isMember": true,
  "couponsApplied": 1
}