LwM2M - BinaryAppDataContainer ambiguity/error

[davidahoward]

Lightweight M2M – Binary App Data Container
Approved Version 1.0.1 – 21 Feb 2019
OMA-TS-LWM2M_BinaryAppDataContainer-V1_0_1-20190221-A
https://www.openmobilealliance.org/release/LwM2M_APPDATA/

There are several differences between the definition of Object 19 Resource 0 and the diagrams in the document.
/19 is defined a multiple object instances, AND multiple resource instances.

So the format of the URI is /<Object ID>/<Instance ID>/<Resource ID>/<Instance ID>, but the figures show it without the resource instance designation e.g. /19/X/0 rather than /19/X/0/Y, where X is the object instance and Y is the resource instance.

This has led to implementation interoperability problems between various clients and servers.

From: OMA-TS-LWM2M_BinaryAppDataContainer-V1_0_1-20190221-A

5.2 LwM2M Client Reports Application Data

Figure 2: LwM2M Client Reports Application Data
1 Observe /19/X/0 token=12xxx
4 Notify /19/X/0 token=12xxx content

##this needs to be clarified. Is the server trying to observe all resource instances? Is the client trying to notify multiple instances?
##If not, this should be /19/X/0/Y

Step 1: The LwM2M Server sends the Observe request to LwM2M Client by instant X of Object 19. The instant number is specified in section 6.

##this needs to be clarified. Is the server trying to observe all resource instances?

5.3 LwM2M Server Sends Application Data

Figure 3: LwM2M Server Sends the Application Data
2 Write /19/X/0 token=13XXX

##this needs to be clarified. Is the server trying to send multiple instances?
##if not, this should be /19/X/0/Y

6. LwM2M Object: Application Data Container
ID Name Operations Instances
0 Data RW Multiple

Additionally, the lwm2m-registry also defines the object and resource as multiple instances https://github.com/OpenMobileAlliance/lwm2m-registry/blob/prod/19.xml

[davidahoward]

The specific problem I am seeing is that the server does a read, or observe to object /19/X/0 (which is defined as a multi instance resource) and the client Notify response is in single instance format, and the server says it is expecting multi instance.

[davidahoward]

The figures are technically correct - but i know people have interpreted them incorrectly --- so clarification around multiple instance resources is what I am looking for. The figures would also be correct (and less open to interpretation) if the explicitly indicated the resource instance e.g. /19/X/0/Y. Where X is the object instance, and Y is the resource instance.

[hannestschofenig]

Mojan suggested to reference the CORE specification for the observation case. For the write case Mojan suggests a clarification and to double-check the CORE spec. Maybe also add information about what the example is trying to show.