SCRA Schema¶

Semantic Specification for the Smart City Reference Architecture (SCRA)

SCRA Schema provides the semantic specification for the Smart City Reference Architecture (SCRA).

It defines the canonical semantic foundation for interoperable smart cities, mobility systems, digital twins, and AI-ready information exchange.

Rather than defining implementation-specific APIs or software platforms, SCRA Schema establishes common semantic concepts, vocabularies, and relationships that enable heterogeneous systems to exchange information through shared meaning.

The specification is designed to align with linked data principles and international standards, including NGSI-LD, RDF, JSON-LD, GTFS, GTFS-Realtime, and Transmodel.

Scope¶

SCRA Schema defines canonical semantic concepts, vocabularies, and semantic relationships for interoperable smart-city information exchange.

The specification focuses on semantic interoperability and does not define implementation-specific solutions.

Specifically, SCRA Schema does not define:

Communication protocols
APIs
Software implementations
Broker architectures
Deployment models
Internal system designs

Those concerns are intentionally delegated to implementation-specific architectures and standards.

This separation allows the semantic foundation to remain stable while supporting multiple implementation technologies, including NGSI-LD, JSON-LD, RDF, Model Context Protocol (MCP), and future interoperability frameworks.

Purpose¶

SCRA Schema provides the semantic foundation of SCRA.

Its objectives are:

Define canonical semantic models
Provide machine-readable semantic models and vocabularies
Support AI interoperability
Enable cross-domain semantic consistency
Promote long-term interoperability

Vision¶

Modern cities operate through many independent information systems.

Although these systems frequently describe the same real-world entities, they often use incompatible data structures and proprietary interfaces.

SCRA establishes a common semantic layer that allows information to be shared, integrated, and interpreted consistently across domains.

The long-term vision is an open semantic ecosystem supporting public agencies, private operators, digital twins, mobility services, and AI applications.

Documentation Structure¶

The documentation is organised into several complementary sections.

Specifications¶

Normative specification documents describing the architecture and semantic framework.

Architecture Decision Records (ADR)¶

Design decisions explaining why particular semantic approaches were adopted.

Semantic Models¶

Canonical definitions of entities, properties, and relationships.

JSON-LD Contexts¶

Machine-readable linked-data vocabularies.

Examples¶

Reference examples demonstrating practical semantic modelling.

Current Status¶

SCRA Schema is under active development.

The current work focuses on semantic models for public transport, real-time mobility information, and AI interoperability.

Future work will extend the semantic framework to additional smart-city domains.

Repository¶

The source repository is available on GitHub.

https://github.com/shwatch/scra-schema