What is YAML? – Simply explained

1. What Does YAML Mean?

YAML stands for “YAML Ain’t Markup Language” (originally “Yet Another Markup Language”). It is a data serialization language specifically designed for human readability.

Core Features:

• Indentation-based structure instead of brackets or tags
• Support for comments (#)
• Language-independent and cross-platform
• Superset of JSON – every JSON file is valid YAML

Technical Details:

• File extensions: .yml or .yaml
• Developed: 2001
• Current specification: YAML 1.2

2. How Does YAML Syntax Work?

YAML uses indentation for structuring. No brackets, semicolons, or closing tags required – making it particularly clear.

Basic Elements:

Scalar Values: Simple values like strings, numbers, or booleans are written directly as key-value pairs.

Lists: Lists are introduced with a hyphen (-) and allow listing multiple values.

Nested Structures: Complex hierarchical data structures can be represented through indentation – ideal for production lines, machine configurations, or system parameters.

yaml

# Scalar values
name: "Production plant Hamburg"
active: true
temperature: 42.5

# Lists
machines:
  - Lathe
  - Milling machine
  - Welding robot

# Nested structures
production_line:
  location: Hamburg
  capacity: 1000
  machines:
    - id: M001
    type: CNC milling machine
    status: active
    - id: M002
    type: Lathe
    status: maintenance

Important Syntax Rules:

• Indentation with 2 spaces (no tabs!)
• Lists begin with -
• Comments with #
• Key and value separated by :

3. YAML in Industry 4.0 & Best Practices

In modern production environments, YAML is indispensable for automation and orchestration of IT/OT systems.

Main Applications:

Container Orchestration with Kubernetes: Definition of deployments, services, and configurations for containerized MES systems, production control, and IoT applications in smart factories.

Docker Compose for Edge Computing: Multi-container applications for edge data processing, local databases, and integration of OPC Router in container environments.

CI/CD Pipelines: Automated build, test, and deployment processes for production software, enabling rapid updates without production interruption.

Infrastructure as Code (IaC): Management of IT infrastructure as code for cloud resources, edge devices, and hybrid production environments.

Typical Use Cases:

• Configuration of microservices and container applications
• Automated deployment processes
• API specifications (OpenAPI/Swagger)
• Configuration management with Ansible
• Logging and monitoring setups

Best Practices:

Consistent Indentation: Always use 2 spaces per level, never tabs. Inconsistent indentation leads to parsing errors.

Comments for Documentation: Use # for comments to document configurations and increase maintainability.

Use Validation: Utilize YAML linters like yamllint, schema validation with JSON Schema, and integrate automatic checks into your CI/CD pipeline.

Mind Security: Always use safe-loading functions (e.g., yaml.safe_load() in Python). Never use unsafe yaml.load(). Validate and sanitize all inputs.

Reuse with Anchors: YAML supports anchors (&) and aliases (*) for reusing configuration blocks, reducing redundancy and improving maintainability.

4. YAML vs. JSON vs. XML: The Comparison

When to Use Which Format?

Use YAML for:

• Configuration files edited by humans
• DevOps tools (Kubernetes, Ansible, Docker Compose)
• Infrastructure as Code
• CI/CD pipeline definitions

Use JSON for:

• REST APIs and web services
• Data exchange between systems
• Browser-based applications

Use XML for:

• Legacy systems and enterprise software
• SOAP web services
• When XML schemas are required

5. OPC Router and YAML-Based Systems

The OPC Router enables seamless integration of YAML-configured systems into your Industry 4.0 infrastructure.

Integration of Containerized Applications:

• Connection of Kubernetes clusters to OPC UA servers
• Docker container communication with production systems
• Microservices integration into existing MES landscapes

Cloud-Native Scenarios:

• Hybrid cloud architectures (on-premise + cloud)
• Edge-to-cloud data pipelines
• DevOps workflows for OT environments

Configuration Management:

• Central management of system configurations
• Version control for production parameters
• Automated configuration distribution

6. Frequently Asked Questions About YAML

7. Conclusion: YAML as the Standard for Modern Configuration

YAML has established itself as the de facto standard for configuration files in cloud-native and DevOps environments. The human-readable syntax reduces errors, accelerates development, and makes configurations maintainable.

In Industry 4.0, YAML enables orchestration of complex container landscapes, automated deployments, and Infrastructure as Code – prerequisites for agile, scalable production environments.

The OPC Router makes these modern technologies accessible to industrial companies, without programming effort and with seamless integration into existing OT/IT systems.

8. Technical Terms Explained

Container Orchestration: Automated management, scaling, and networking of container applications.

Infrastructure as Code (IaC): Management of IT infrastructure through machine-readable configuration files instead of manual processes.

CI/CD: Continuous Integration/Continuous Deployment – automated build, test, and deployment processes.

Kubernetes: Open-source platform for orchestrating containerized applications.

Docker Compose: Tool for defining and running multi-container Docker applications.

DevOps: Combination of software development (Dev) and IT operations (Ops) for faster, more reliable releases.

Safe-Loading: Secure parsing of YAML files without code execution.

Anchor & Alias: YAML feature for reusing configuration blocks.