Table of Contents Introduction: Why OPC UA Became the "Standard Language" of the Industrial Internet Era Background and Development History of OPC UA 2.1 The Birth of OPC Classic 2.2 The Proposal and Vision of OPC UA 2.3 International Standardization and Ecosystem Development Overall Architecture of OPC UA 3.1 Future-Oriented Cross-Platform Architecture 3.2 Communication Stack Structure 3.3 Information Model and Data Organization Core Technical Features of OPC UA 4.1 Security