OGC SensorThings API Schema Validator

Abstract

This tool provides automated validation of entities stored in OGC SensorThings API implementations against organization-specific JSON Schema definitions. The OGC SensorThings API is an open geospatial standard for interconnecting Internet of Things (IoT) devices, data, and applications over the Web, providing a unified framework for managing sensor data and observations.

As SensorThings API implementations grow in scale and complexity, ensuring data quality and compliance with organizational requirements becomes critical. This validation tool addresses the need for systematic quality assurance by enabling configurable, schema-driven validation of entity properties beyond the base OGC specification requirements.

Standards & Specifications

This implementation is designed to work with:

OGC SensorThings API Part 1: Sensing (Version 1.1) - The core specification defining the data model and REST API for IoT sensor observations (OGC Document 18-088)
JSON Schema Draft 2020-12 - The validation schema language used to define entity constraints

Compatible Implementations

This tool has been tested with:

FROST-Server - The Fraunhofer IOSB reference implementation of the OGC SensorThings API, widely used in production environments
Any OGC SensorThings API 1.0/1.1 compliant server implementation

Overview

SensorThings API Data Model

The OGC SensorThings API defines a standard data model consisting of eight core entity types that capture the "who, what, when, where, and how" of sensor observations:

Thing - The object of interest (e.g., a weather station, vehicle, building)
Location - The geographic location of a Thing
HistoricalLocation - Historical location information
Datastream - A collection of observations grouped by sensor and observed property
Sensor - The instrument or procedure that produced the observations
ObservedProperty - The phenomenon being measured (e.g., temperature, humidity)
Observation - The actual measurement or result
FeatureOfInterest - The feature that is the subject of an observation

This validator enables organizations to enforce custom validation rules on any of these entity types through JSON Schema definitions.

Features

Standards-Based Validation: Implements JSON Schema Draft 2020-12 for validation rule definition
Comprehensive Coverage: Supports all OGC SensorThings API entity types
Flexible Validation Scope: Validate individual entities, entity types, or entire datasets
Multiple Output Formats: Console, JSON, and CSV reporting for different use cases
Continuous Monitoring: Scheduled validation runs for ongoing data quality assurance
Nested Property Support: Full validation of nested object structures and custom properties
Custom Extensions: Organization-specific error messages and severity levels
Configurable Architecture: YAML-based configuration with entity-specific settings
Production Ready: Docker images, Docker Compose, and CI/CD workflows
Authentication Support: Multiple authentication methods including Basic Auth, Bearer tokens, and Keycloak OIDC

Quick Start

🎯 Quick Demo (5 Minutes)

Want to see the validator in action right away? Try the fully automated demo:

# Clone the repository
git clone https://github.com/janbeckert/ogc-sta-schema-validator.git
cd ogc-sta-schema-validator

# Run the demo (requires Docker and Docker Compose)
./demo.sh

This will:

Start a complete FROST-Server environment
Provision sample entities (both valid and invalid)
Run validation and show results with intentional errors
Demonstrate the validator catching real data quality issues

Or use Docker Compose directly:

docker compose up --build

The demo shows validation catching common errors like missing required fields, invalid data types, out of range values, and malformed dates.

Option 1: Docker (Recommended for Quick Testing)

The easiest way to get started is using Docker:

# Pull the latest image from GitHub Container Registry
docker pull ghcr.io/janbeckert/ogc-sta-schema-validator:latest

# Or build locally
docker build -t ogc-sta-schema-validator .

# Run a simple test (show help)
docker run --rm ogc-sta-schema-validator

# Test connection to a FROST-Server
docker run --rm \
  -e VALIDATOR_SERVER__URL=http://your-server:8080/FROST-Server/v1.1 \
  ogc-sta-schema-validator \
  test-connection

# Validate with your own config and schemas
docker run --rm \
  -v $(pwd)/config:/app/config:ro \
  -v $(pwd)/schemas:/app/schemas:ro \
  -v $(pwd)/output:/app/output \
  ogc-sta-schema-validator \
  validate --entity-type Things --output-file /app/output/report.json

Option 2: Local Installation

This project uses uv for dependency management.

# Install uv if you haven't already
curl -LsSf https://astral.sh/uv/install.sh | sh

# Clone and setup the project
cd ogc-sta-schema-validator

# Install dependencies
uv sync

# Activate the virtual environment
source .venv/bin/activate  # On Unix/macOS
# or
.venv\Scripts\activate     # On Windows

Configuration

Copy the example configuration file:

cp config/config.example.yaml config/config.yaml

Edit config/config.yaml with your server details:

server:
  url: "http://your-frost-server:8080/FROST-Server/v1.1"

Configure authentication if required (see config file for examples)
Set up your validation schemas:

# Option 1: Copy example schemas
cp examples/schemas/*.json schemas/

# Option 2: Create custom schemas in schemas/ directory

Basic Usage

# Test connection to your FROST-Server
uv run ogc-sta-validate test-connection

# List available entity types
uv run ogc-sta-validate list-entities

# Validate all Things
uv run ogc-sta-validate validate --entity-type Things

# Validate a specific Thing
uv run ogc-sta-validate validate --entity-type Things --entity-id 123

# Validate with custom schema
uv run ogc-sta-validate validate --entity-type Things --schema schemas/thing_schema.json

# Generate JSON report
uv run ogc-sta-validate validate --entity-type Things --output-format json --output-file report.json

# Validate all entity types
uv run ogc-sta-validate validate-all

# Run continuous validation (every 30 minutes)
uv run ogc-sta-validate continuous --interval 1800

Configuration

The tool supports multiple configuration sources with the following precedence (highest to lowest):

CLI arguments (highest priority)
Environment variables
YAML configuration file
Default values (lowest priority)

This flexible approach allows you to:

Store sensitive credentials in environment variables
Override configuration temporarily via CLI arguments
Maintain base configuration in YAML files
Use different configurations across environments (dev/staging/prod)

Method 1: YAML Configuration File

The primary configuration method uses YAML files. This is covered in the Quick Start section above.

# config/config.yaml
server:
  url: "http://localhost:8080/FROST-Server/v1.1"
  timeout: 30
  auth:
    method: "basic"
    username: "user"
    password: "pass"

validation:
  batch_size: 100
  stop_on_error: false

See config/config.example.yaml for a complete configuration template with all available options.

Method 2: Environment Variables

Environment variables can override YAML configuration values. This is especially useful for:

Sensitive data: Store credentials securely outside of config files
CI/CD pipelines: Configure differently across environments
Docker deployments: Use Docker environment variables

Naming Convention

Environment variables use the prefix VALIDATOR_ and double underscores (__) for nested values:

# Format: VALIDATOR_<SECTION>__<KEY>
VALIDATOR_SERVER__URL=http://example.com/v1.1
VALIDATOR_SERVER__TIMEOUT=60
VALIDATOR_VALIDATION__BATCH_SIZE=200

Quick Setup

# Copy the example environment file
cp .env.example .env

Example Environment Variables

# Server configuration
export VALIDATOR_SERVER__URL="http://example.com/FROST-Server/v1.1"
export VALIDATOR_SERVER__TIMEOUT=60

# Authentication (recommended for sensitive credentials)
export VALIDATOR_SERVER__AUTH__METHOD="basic"
export VALIDATOR_SERVER__AUTH__USERNAME="myuser"
export VALIDATOR_SERVER__AUTH__PASSWORD="mypassword"

# Validation settings
export VALIDATOR_VALIDATION__BATCH_SIZE=200
export VALIDATOR_OUTPUT__FORMAT="json"

# Now run the tool - environment variables will be used
uv run ogc-sta-validate test-connection

See .env.example for all available environment variables.

Method 3: CLI Arguments

CLI arguments provide the highest precedence.

Common CLI Options

# Override server URL
uv run ogc-sta-validate --server-url http://example.com/v1.1 test-connection

# Override timeout
uv run ogc-sta-validate --timeout 60 test-connection

# Override batch size
uv run ogc-sta-validate --batch-size 200 validate --entity-type Things

# Combine multiple overrides
uv run ogc-sta-validate \
  --server-url http://example.com/v1.1 \
  --timeout 60 \
  --batch-size 200 \
  validate --entity-type Things

Command-Specific Options

Each command also has specific options:

# Validate command options
uv run ogc-sta-validate validate \
  --entity-type Things \
  --limit 100 \
  --output-format json \
  --output-file report.json \
  --filter "properties/status eq 'active'"

# Continuous validation options
uv run ogc-sta-validate continuous \
  --interval 3600 \
  --entity-types Things \
  --entity-types Sensors \
  --max-entities 500

Getting Help

View all available CLI options:

# Main help
uv run ogc-sta-validate --help

# Command-specific help
uv run ogc-sta-validate validate --help
uv run ogc-sta-validate continuous --help

Validation Methodology

Approach

This tool implements a schema-driven validation approach that operates independently of the OGC SensorThings API server's internal validation. While the SensorThings API specification defines mandatory properties and data types, organizations often have additional requirements such as:

Custom property schemas for domain-specific metadata
Enumerated value constraints for controlled vocabularies
Pattern matching for identifiers following organizational conventions
Range validation for sensor measurements
Date/time format requirements beyond ISO 8601

The validation engine retrieves entities via the SensorThings API's standardized REST interface and applies JSON Schema rules without modifying the source data, making it suitable for both development and production environments.

Validation Process

Entity Retrieval: Fetches entities from the SensorThings API server using HTTP GET requests with optional OData filtering
Schema Loading: Loads JSON Schema definitions from the local filesystem, matched by entity type
Rule Application: Applies JSON Schema validation rules using the jsonschema library
Error Aggregation: Collects validation errors with property paths and rule type information
Report Generation: Produces detailed reports in multiple formats (console, JSON, CSV)

Architecture

The validator implements a modular architecture with separation of concerns:

┌─────────────────┐
│  CLI Interface  │  Command-line interface (Click framework)
│   (cli.py)      │
└────────┬────────┘
         │
         ├──┬──────────────────────────────────────────────────┐
         │  │                                                  │
┌────────▼──────────┐  ┌──────────────┐  ┌──────────────────┐  │
│   API Client      │  │Schema Loader │  │ Validator Engine │  │
│(api_client.py)    │  │(loader.py)   │  │ (validator.py)   │  │
│                   │  │              │  │                  │  │
│ - HTTP requests   │  │- JSON Schema │  │ - Rule engine    │  │
│ - Pagination      │  │  discovery   │  │ - Error handling │  │
│ - Auth strategies │  │- Validation  │  │ - Type checking  │  │
│ - OData filters   │  │              │  │                  │  │
└────────┬──────────┘  └──────┬───────┘  └────────┬─────────┘  │
         │                    │                   │            │
         │                    │                   │            │
         └────────────────────┴───────────────────┴────────────┤
                                                               │
                            ┌──────────────────────────────────▼┐
                            │      Validation Runner            │
                            │         (runner.py)               │
                            │                                   │
                            │ - Orchestration & batch processing│
                            │ - Multi-format report generation  │
                            │ - Error/warning categorization    │
                            └───────────────────────────────────┘

JSON Schema Format

Validation schemas use standard JSON Schema Draft 2020-12. This example demonstrates common validation features:

{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://schemas.sensorthings.org/things.json",
  "title": "Things Schema",
  "type": "object",
  "required": ["name", "description"],
  "properties": {
    "name": {
      "type": "string",
      "minLength": 1,
      "maxLength": 100,
      "description": "Thing name is mandatory",
      "x-errorMessage": "Thing must have a non-empty name (1-100 characters)"
    },
    "description": {
      "type": "string",
      "minLength": 1
    },
    "properties": {
      "type": "object",
      "required": ["thingId"],
      "properties": {
        "thingId": {
          "type": "string",
          "minLength": 1
        },
        "status": {
          "enum": ["active", "inactive", "maintenance"],
          "description": "Status must be one of the allowed values"
        },
        "code": {
          "type": "string",
          "pattern": "^[A-Z]{2}[0-9]{4}$",
          "description": "Building code format: two uppercase letters + four digits"
        },
        "temperature": {
          "type": "number",
          "minimum": -50,
          "maximum": 100
        },
        "timestamp": {
          "type": "string",
          "format": "date-time"
        },
        "coordinates": {
          "type": "array",
          "minItems": 2,
          "maxItems": 3,
          "description": "Coordinates [longitude, latitude, altitude?]"
        },
        "tags": {
          "type": "array",
          "minItems": 1,
          "maxItems": 10
        }
      }
    }
  }
}

See JSON Schema specification for complete documentation.

Custom Extensions

This validator supports custom JSON Schema extension fields (prefixed with x- per JSON Schema conventions) to enhance validation functionality:

Schema-Level Extensions

x-version (string, optional): Schema version identifier for tracking and documentation

{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "x-version": "2.0.0",
  "x-entityType": "Things",
  "title": "Things Schema"
}

x-entityType (string, optional): Specifies the SensorThings API entity type this schema validates

{
  "x-entityType": "Things"
}

Used for entity type identification when the schema filename doesn't match the entity type.

Property-Level Extensions

x-errorMessage (string, optional): Custom error message shown when validation fails

{
  "type": "string",
  "pattern": "^de\\.sn\\.stlp\\..+",
  "x-errorMessage": "ID must start with Leipzig prefix (de.sn.stlp.)"
}

x-severity (string, optional): Validation severity level - either "error" or "warning"

{
  "type": "string",
  "pattern": "^[A-Z]{2}[0-9]{4}$",
  "x-errorMessage": "Recommended format: XX9999",
  "x-severity": "warning"
}

error (default): Validation failure causes entity to be marked as invalid
warning: Validation failure is reported but entity remains valid

Complete Example

{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://schemas.sensorthings.org/things.json",
  "x-version": "2.0.0",
  "x-entityType": "Things",
  "title": "Things Schema",
  "type": "object",
  "required": ["name"],
  "properties": {
    "name": {
      "type": "string",
      "minLength": 1,
      "x-errorMessage": "Thing must have a non-empty name"
    },
    "properties": {
      "type": "object",
      "properties": {
        "thingId": {
          "type": "string",
          "pattern": "^de\\.sn\\.stlp\\..+",
          "x-errorMessage": "Thing ID must use Leipzig prefix",
          "x-severity": "error"
        },
        "installationDate": {
          "type": "string",
          "format": "date-time",
          "x-errorMessage": "Installation date should be in ISO 8601 format",
          "x-severity": "warning"
        }
      }
    }
  }
}

CLI Commands

test-connection

Test connection to the SensorThings API server.

validate

Validate entities of a specific type.

Options:

--entity-type, -t: Entity type to validate (required)
--entity-id, -i: Specific entity ID to validate
--schema, -s: Schema file to use
--limit, -l: Maximum number of entities to validate
--filter, -f: OData filter expression
--output-format: Output format (console, json, csv)
--output-file, -o: Output file path
--include-valid: Include valid entities in output

validate-all

Validate all entity types.

Options:

--entity-types, -t: Specific entity types to validate
--limit-per-type, -l: Maximum entities per type
--output-format: Output format
--output-file, -o: Output file path
--include-valid: Include valid entities in output

continuous

Run continuous validation.

Options:

--interval, -i: Validation interval in seconds
--entity-types, -t: Entity types to validate
--max-entities, -m: Maximum entities per run

validate-schema

Validate schema files.

Options:

--schema-file, -s: Specific schema file to validate

list-entities

List available entity types and their counts.

Development

Setup Development Environment

# Install with development dependencies
uv sync --dev

# Run tests
uv run pytest

# Format code and fix imports (replaces black + isort)
uv run ruff format .

# Lint code (replaces flake8)
uv run ruff check .

# Lint and auto-fix issues
uv run ruff check --fix .

Adding Dependencies

# Add a new dependency
uv add requests

# Add a development dependency
uv add --dev pytest

# Update dependencies
uv sync

Example Validation Schemas

The repository includes example validation schemas in examples/schemas/ demonstrating validation patterns for common SensorThings API entity types:

examples/schemas/thing_schema.json - Validation schema for Thing entities with custom property constraints
examples/schemas/sensor_schema.json - Validation schema for Sensor entities with metadata requirements
examples/schemas/observation_schema.json - Validation schema for Observation entities with result value constraints
examples/schemas/datastream_schema.json - Validation schema for Datastream entities with unit of measurement validation

Copy these to your schemas/ directory and customize them for your organization:

cp examples/schemas/*.json schemas/

See examples/schemas/README.md for customization guidance.

Output Formats

Console Output

Human-readable text format with validation summary and error details.

JSON Output

Structured JSON format suitable for programmatic processing:

{
  "summary": {
    "total_entities": 100,
    "valid_entities": 95,
    "invalid_entities": 5,
    "total_errors": 8,
    "total_warnings": 2
  },
  "results": [
    {
      "entityId": "123",
      "entityType": "Things",
      "isValid": false,
      "errors": [
        {
          "property_path": "properties.building",
          "message": "Required field is missing",
          "validator": "required"
        }
      ]
    }
  ]
}

CSV Output

Tabular format suitable for spreadsheet analysis with columns:

EntityType, EntityId, IsValid, ErrorCount, WarningCount, PropertyPath, ErrorType, Message, Severity

Troubleshooting

Connection Issues

Verify the SensorThings API server URL conforms to the specification (e.g., ends with /v1.0 or /v1.1)
Check network connectivity and firewall rules
Ensure authentication credentials are correct for your server's authentication method

Schema Issues

Use validate-schema command to check JSON Schema validity against Draft 2020-12
Verify JSON syntax and required meta-properties ($schema, type, etc.)
Ensure custom extensions (x-errorMessage, x-severity) follow the expected format

Performance

Adjust batch_size based on entity complexity and network latency (typical range: 50-500)
Use OData $filter expressions to limit validation scope to relevant entities

License

See LICENSE file for details.

Contributing

Contributions are welcome! Please feel free to submit a Pull Request. For major changes, please open an issue first to discuss what you would like to change.

Name		Name	Last commit message	Last commit date
Latest commit History 2 Commits
.github/workflows		.github/workflows
config		config
examples		examples
src		src
tests		tests
.dockerignore		.dockerignore
.env.example		.env.example
.gitignore		.gitignore
CHANGELOG.md		CHANGELOG.md
Dockerfile		Dockerfile
LICENSE		LICENSE
README.md		README.md
demo.sh		demo.sh
docker-compose.yml		docker-compose.yml
pyproject.toml		pyproject.toml
requirements.txt		requirements.txt
uv.lock		uv.lock

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OGC SensorThings API Schema Validator

Abstract

Standards & Specifications

Compatible Implementations

Overview

SensorThings API Data Model

Features

Quick Start

🎯 Quick Demo (5 Minutes)

Option 1: Docker (Recommended for Quick Testing)

Option 2: Local Installation

Configuration

Basic Usage

Configuration

Method 1: YAML Configuration File

Method 2: Environment Variables

Naming Convention

Quick Setup

Example Environment Variables

Method 3: CLI Arguments

Common CLI Options

Command-Specific Options

Getting Help

Validation Methodology

Approach

Validation Process

Architecture

JSON Schema Format

Custom Extensions

Schema-Level Extensions

Property-Level Extensions

Complete Example

CLI Commands

test-connection

validate

validate-all

continuous

validate-schema

list-entities

Development

Setup Development Environment

Adding Dependencies

Example Validation Schemas

Output Formats

Console Output

JSON Output

CSV Output

Troubleshooting

Connection Issues

Schema Issues

Performance

License

Contributing

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