OCA Technical Specification

Overlays Capture Architecture (OCA) is a technical specification for creating and managing digital schemas with layered metadata. It provides a framework for capturing, validating, transforming, and presenting data while maintaining semantic integrity across different systems and contexts.

The architecture consists of a stable Capture Base that defines core data structures, combined with task-specific Overlays that add contextual information and functionality. This separation allows for flexible schema evolution while preserving data meaning and relationships.

Key differentiating features include:

• Cryptographically-linked layers that ensure data integrity
• Language-independent base structure with localized overlays
• Support for multiple presentation formats without changing the base schema
• Built-in privacy controls through attribute flagging
• Extensible overlay system for adding new functionality

The specification is maintained by the Decentralised Semantics Working Group at the Human Colossus Foundation.

Purpose and Scope:

• Define a standardized approach for creating interoperable data schemas
• Enable semantic preservation across different systems and contexts
• Support data validation, transformation, and presentation requirements
• Facilitate privacy-preserving data exchange

Key Technical Specifications:

1. Capture Base:

   • Defines core data structure and attributes
   • Supports seven data types: Text, Numeric, Reference, Boolean, Binary, DateTime, Array
   • Includes flagging for sensitive attributes

2. Overlays:

   • Semantic Overlays: Add meaning and context
   • Input Overlays: Define data capture rules
   • Transformation Overlays: Handle data conversion
   • Presentation Overlays: Control display formatting

Implementation Requirements:

• Must implement SAID (Self-Addressing IDentifier) for object references
• Must support JSON as minimum serialization format
• Must include required overlays in bundles:
  • Character encoding
  • Format
  • Capture base

Security Considerations:

• Cryptographic linking between layers
• Built-in PII/QII flagging capabilities
• Support for attribute-level encryption
• Sensitive data handling controls

Interoperability Features:

• Language-independent base structure
• Support for multiple character encodings
• Standardized unit conversion
• Cross-schema mapping capabilities

Current Adoption Status:

• Specification version: v1.0.1
• Maintained through open governance model
• Active development and community contribution