Re: New Device Services & SDK Requirements document (v5)


espy
 

On 03/06/2018 06:17 AM, Drasko DRASKOVIC wrote:
Hi Tony,
in your doc I can see that query commands sometime return strings:
{"AnalogValue_40":"183.92999267578125"}
Yes, that's correct.

This is simple, and of course make sense, just that ints, floats and
bools are all represented by strings and I guess that make messages
longer. It's not an issue now, but in the future, we might think about
constrained and battery-powered devices which send messages over
LPWAN, potentially aggregate several sensor readings and then send
them all at once (this is typical mode of operation).
IETF is trying to define semantics for sensor network JSON and CBOR
mesages through SenML standard:
https://tools.ietf.org/html/draft-ietf-core-senml-13
SenML is describing the type of the value, and can shorten the
aggregated messages. I think it is worth looking at.
Thanks for the suggestion! It looks like this is still a draft, so we should keep any eye on it as it progresses.

Some observations:

- the readings embed the device name, making it possible to combine readings from different devices in the same result array. EdgeX currently adds the device name to the event, which contains readings.

- the format allows custom attributes to be defined, which would allow us to add EdgeX specific attributes

- I don't think there's a big difference in size between our current messages and the JSON SenML format, in fact the latter messages might even be a bit larger than our current messages. That said, on constrained devices using CBOR would be an advantage.

Implementing this would require pretty invasive re-work across all of our services, so this is something we should put on our post-California architecture list.

Regards,
/tony



Best regards,
Drasko DRASKOVIC
Mainflux Author and Technical Advisor
www.mainflux.com | Industrial IoT Cloud
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Engineering Division | Paris, France
LinkedIn: https://www.linkedin.com/in/draskodraskovic
Twitter: @draskodraskovic
On Tue, Mar 6, 2018 at 2:01 AM, espy <espy@...> wrote:
Attached please find the latest Device Services & SDK Requirements document
(v5) for the California release of EdgeX Foundry.

Thanks for those of you that provided feedback on the previous version!

The following areas of the document have been clarified or updated:

* Query commands:
- mention that readings are triggered whenever a successful query command
is processed
- clarify which Query GET handlers are required

* Data transformation - new section

* Actuation commands - clarified how command arguments are passed

* operatingState - clarified how device operatingStates are handled

* Security - new section

* Appendix A - Settings: minor cleanup

There still is some remaining work to flesh out the logging, scheduling, and
metadata updates sections.

Please review and send my comments my way.

Regards,
/tony

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