Business intent over hardware instructions
Applications request operations such as start_cycle, not relay timing or register writes.
FOUNDATION · EXPLANATORY
Design principles that keep SDL from becoming another proprietary integration layer.
These principles guide specifications, reference software and future project proposals.
Stable asset identity
A machine keeps the same operational identity when its controller or wiring changes.
Capability-based interoperability
Applications discover what an asset supports instead of assuming behavior from its type.
Local-first execution
Real-time validation, safety and physical execution remain available at the site.
Commands are requests; events are facts
Sending a command is not evidence that the requested physical result occurred.
Acceptance, execution and confirmation differ
The architecture distinguishes validation, hardware action and observed machine state.
Idempotency before retry
Duplicate delivery must not cause duplicate paid cycles or repeated physical actions.
Expired commands do not become future actions
Delayed time-sensitive commands are rejected rather than executed after reconnection.
State reflects confidence
Unknown, offline and stale states are never silently treated as idle.
Safety decisions stay near the device
Pump timeouts, interlocks and output limits are enforced locally.
Configuration is versioned operational data
Mappings and safety values are validated, auditable and recoverable.
Specifications define meaning; bindings define transport
Core semantics remain independent of MQTT, HTTP or future transports.
DECISION CHECKLIST
Every future SDL proposal should answer these questions.
- Does it expose business intent or hardware detail?
- What happens when the cloud is unavailable?
- How is physical success confirmed?
- Can a duplicate command cause a repeated action?
- What is the safe failure behavior?
- Can the behavior be simulated and tested?
- Does it preserve compatibility with the shared core?
- Is the feature documented clearly enough for another implementation?