Using negative value in write attributes ?

[sbernard31]

Is it possible to use negative value in write attribute, especially for Greater Than and Less Than ?

The specification LWM2M-v1.2.1@core§Table: 7.3.2.-1 class Attributes says this is not possible :

Attribute Name	CoRE Link param	Attachment	Access Mode	Value Type	Default Value	Applicability
Greater Than	"gt" "=" 1DIGIT ["." 1DIGIT]	ResourceResource Instance	RW	Float	-	Numerical & Readable Resource
Less Than	"lt" "=" 1DIGIT ["." 1DIGIT]	ResourceResource Instance	RW	Float	-	Numerical & Readable Resource

Is it intended or is it a bug ?

[sbernard31]

Note that LWM2M-v1.2.1@core§Table: 7.3.2.-1 class Attributes also says :

The behaviour of Notification class attributes MUST follow [Cond_Attr] unless stated otherwise in this specification.

And [Cond_Attr§ 3.1. Conditional Notification Attributes ] says :

Attribute	Name	Value
Greater Than	c.gt	xs:decimal
Less Than	c.lt	xs:decimal
Change Step	c.st	xs:decimal (>0)

So it seems there is a contradiction between both specification.

[sbernard31]

Note there also a difference with pmin, pmax, epmin and epmax.
In LWM2M they are considered as Integer and in Cond_attr there are decimal.

[mojanm]

As "c.gt" and "c.lt" IETF core conditional attributes that are supposed to be aligned with LWM2M attributes can be less than 0, can assume Table 7.3.2.1 in LwM2M spec needs to be updated to reflect this.

[sbernard31]

@mojanm thx for the answer, this really helps. 🙏
I will be able to update Leshan behavior.

What about pmin, pmax, epmin and epmax ?

Attribute Name	CoRE Link param
Minimum Period	"pmin" "=" 1*DIGIT
Maximum Period	"pmax" "=" 1*DIGIT
Minimum Evaluation Period	"epmin" "=" 1*DIGIT
Maximum Evaluation Period	"epmax" "=" 1*DIGIT

(from LWM2M-v1.2.1@core§Table: 7.3.2.-1 class Attributes)

I guess it should be adapted too? Replacing 1*DIGIT by 1*DIGIT ["." 1*DIGIT] ?

because :

Attribute	Name	Value
Minimum Period (s)	c.pmin	xs:decimal (>0)
Maximum Period (s)	c.pmax	xs:decimal (>0)
Minimum Evaluation Period (s)	c.epmin	xs:decimal (>0)
Maximum Evaluation Period (s)	c.epmax	xs:decimal (>0)

(from [Cond_Attr§ 3.2. Conditional Control Attributes ])