Field categories
Requests can select categories such as momentary, peak, status, computed, identity, and historical data. Ask only for categories and field names the application needs; unconstrained historical reads can be expensive.Communication patterns
Request/response lifecycle
- Send field/category, node, time-range, and optional token filters.
- Receive an acknowledgement with request identity.
- Process zero or more field fragments.
- Stop only when the response marks completion or an error occurs.
- Cancel the request when the result is no longer needed.
Quality and units
Preserve quality flags and timestamp with the value. Convert units through published unit definitions rather than hard-coded display conversions. Never compare readings from incompatible units or silently discard uncertainty/status fields.Subscription hygiene
- Use meaningful thresholds and minimum intervals.
- Renew/monitor subscriptions as required by the device.
- Unsubscribe when the consumer goes away.
- Deduplicate events by request/subscription identity and field timestamp.
- Apply backpressure or aggregation before forwarding high-rate telemetry.