Module validation 

Comprehensive Attribute Validation System

This module provides validation for XML attributes including:

• Required attribute validation
• Format validation (URIs, dates, enums, etc.)
• Custom attribute policy enforcement
• DDEX-specific validation rules
• Cross-attribute validation
• Namespace-aware validation

Structs

AttributeValidator

Comprehensive attribute validator

ElementValidationConfig

Element-specific validation configuration

NamespacePolicy

Namespace-specific validation policy

ValidationPolicy

Validation policy for controlling attribute validation behavior

ValidationResult

Validation result containing errors and warnings

Enums

AttributeValidationError

Comprehensive validation errors for attributes

DependencyCondition

Dependency condition for cross-attribute validation

ValidationRule

Attribute validation rule definition