On Mon, Aug 23, 2021 at 5:17 AM Balázs Lengyel <[email protected]> wrote:
> Hello Rob, > > I think this won’t fly. > > In sections 1.2 and 2 we state: > > *“**Instance data files MAY contain partial data sets.”* > > Which is important for many use-cases. This means you cannot say that a > default value will or must be included, as they might be omitted because they > are not part of the partial data set. > > In a way it is difficult to separate between leaves that are missing because > > - They are not part of the partial data-set > > - They are omitted because they have the default value and one of the > trim or explicit options is used > > If this becomes important the report-all options shall be used. > > > > I thought we already agreed there cannot be a default or there is no way to represent "no defaults added". Note that "report-all" is not useful if basic-mode=explicit, since a leaf reporting the YANG default could be set by the client. Only report-all-tagged will clearly identify defaults in this case. Also note that if basic-mode=report-all then there will be no defaults ever reported. This mode means the server does not consider any node to be a default and always returns every node (if with-defaults used or not). > This is the reason I used the SHOULD word. > > Regards Balazs > > Andy > > > *From:* Rob Wilton (rwilton) <[email protected]> > *Sent:* 2021. augusztus 23., hétfő 12:27 > *To:* Balázs Lengyel <[email protected]>; Andy Bierman < > [email protected]>; NetMod WG <[email protected]> > *Subject:* RE: [netmod] yang-instance-file include-defaults leaf > > > > Hi Balazs, Andy, Netmod, > > > > Sorry for the delayed response. I would still like to strength the > description of the defaults. E.g., RFC 6243 uses MUSTs rather than SHOULDs. > > > > Hence, I have generated some proposed alternative descriptions, that are > somewhat stricter, but also more generically focussed only on the default > values. > > > > With these definitions, I think that we could define the > “include-defaults” default value to be “explicit”, since if the leaf if not > included, then I think that this effectively what the meaning would be > anyway. > > > > > > In particular, I would propose changing the descriptions as follows: > > > > leaf includes-defaults { > > type enumeration { > > enum report-all { > > value 1; > > description > > "All data nodes SHOULD be included independent of > > any default values."; > > } > > enum trim { > > value 2; > > description > > "Data nodes that have a default defined and where > > the actual value is the default value SHOULD > > NOT be included."; > > } > > enum explicit { > > value 3; > > description > > "Data nodes that have a default defined and where > > the actual value is the default value SHOULD NOT be > > included. However, if the actual value was set by > > a NETCONF client or other management application > > by the way of an explicit management operation the > > data node SHOULD be included."; > > } > > } > > > > Proposed: > > > > leaf includes-defaults { > > type enumeration { > > enum report-all { > > value 1; > > description > > "The instance data set includes all data nodes, > > including those that contain the schema default.”; > > } > > enum trim { > > value 2; > > description > > "The instance data set excludes all data nodes > > that contain the schema default."; > > } > > enum explicit { > > value 3; > > description > > "The instance data set may include some data nodes > > that match the schema default and may exclude some > > data nodes that match the schema default.”; > > } > > } > > description > > "This leaf provides an indication of how default data > > is presented within an instance data set, modelled on > > RFC 6243. > > > > Interpretation of the use of defaults depends on the > > context of what the instance data set represents. > > > > E.g., if the instance data set represents configuration, > > Then include-defaults aligns to the meaning of the > > default-handling basic modes in RFC 6243. If the > > instance data set represents operational data from the > > operational state datastore [RFC 8342], then > > include-defaults aligns to the definition of that > > datastore in RFC 8342.”; > > > > Would text along these lines work? > > > > Thanks, > > Rob > > > > > > *From:* Balázs Lengyel <[email protected]> > *Sent:* 28 July 2021 23:08 > *To:* Rob Wilton (rwilton) <[email protected]>; Andy Bierman < > [email protected]> > *Cc:* NetMod WG <[email protected]> > *Subject:* RE: [netmod] yang-instance-file include-defaults leaf > > > > Hello Rob, > > Removing the “default trim;” will address Andy’s comment. > > > > Your *in-use-values* is very specific to one of the use-cases: > reading/documenting operational values. It is not useful for the other > use-cases. I think the “documenting operational datastore” use-case could > be handled by indicating the *includes-defaults=report-all*. Case (i) > would contain the value case (ii) will not. > > Regards Balazs > > > > *From:* Rob Wilton (rwilton) <[email protected]> > *Sent:* 2021. július 27., kedd 17:38 > *To:* Andy Bierman <[email protected]>; Balázs Lengyel < > [email protected]> > *Cc:* NetMod WG <[email protected]> > *Subject:* RE: [netmod] yang-instance-file include-defaults leaf > > > > Hi Andy, Balazs, > > > > So, the reason that I want a flag to indicate whether default values are > in use is because of this definition of operational in RFC 8342: > > > > Requests to retrieve nodes from <operational> always return the value > > in use if the node exists, regardless of any default value specified > > in the YANG module. If no value is returned for a given node, then > > this implies that the node is not used by the device. > > > > It was written this way because otherwise a consumer of operational data > cannot differentiate between: > > (i) This value is not present because it matches the > default value specified in the YANG module, and > > (ii) This value is not present because the server has failed > to return it for some reason (e.g., perhaps the daemon that would have > provided this value is down or not available, or perhaps it is a bug, or > perhaps it is not implemented and is a missing deviation). > > > > So, I think that in some cases, the absence of a data node does not > necessarily mean that the default value is in effect, and I wanted the > instance-data document to be able to contain and correctly report this data. > > > > I think that this behaviour could be captured by a single leaf. Another > way of articulating this would be: > > > > leaf in-use-values { > > type boolean; > > default false; > > description > > “Only if set to true, the absence of a value in the > > instance data for a given data node implies that the > > node is not used rather than implicitly taking the > > default value specified by any corresponding > > ‘default’ statement specified in the YANG schema.”; > > } > > > > With this, I’m not sure whether we need the “includes-default” leaf > currently specified in the draft, but if we do, then I would think that > leaf should be entirely optional, i.e., without the default “trim”. > > > > Regards, > Rob > > > > > > *From:* Andy Bierman <[email protected]> > *Sent:* 10 July 2021 17:41 > *To:* Rob Wilton (rwilton) <[email protected]> > *Cc:* NetMod WG <[email protected]>; Balázs Lengyel < > [email protected]> > *Subject:* Re: [netmod] yang-instance-file include-defaults leaf > > > > > > > > On Fri, Jul 9, 2021 at 5:23 AM Rob Wilton (rwilton) <[email protected]> > wrote: > > Andy, > > > > Yes, when I suggested this, I was thinking that a boolean flag might be > sufficient. My point being that automatically filtering out default values > isn’t always the right thing to do. > > > > > > > > The solution is simple. > > Get rid of the inappropriate "default trim" statement. > > > > If the leaf is present then it identifies the basic-mode that was used to > include defaults. > > If not then the information is either not known, not applicable, or > defaults were not added. > > > > The "default" statement is a bug because there is no default basic-mode. > > All of the basic-modes are in use in deployments and no camp has ever > > been able to convince the others that theirs is right. > > > > > > Andy > > > > E.g., something along these lines: > > > > leaf exclude-defaults { > > type boolean; > > default true; > > description > > “Can be used to reduce the size of the content data file. > > > > When unset or set to true, data nodes that have a default defined and > > where the actual value is the default value are excluded from the > content > > data. > > > > When set to false, data nodes with default value are not filtered, > and > > may appear in the content data.” > > } > > > > Would this satisfy your concern? > > > > Regards, > Rob > > > > > > *From:* netmod <[email protected]> *On Behalf Of *Andy Bierman > *Sent:* 08 July 2021 18:16 > *To:* NetMod WG <[email protected]> > *Subject:* [netmod] yang-instance-file include-defaults leaf > > > > Hi, > > > > The module has this object: > > > > leaf includes-defaults { > > type enumeration { > > enum report-all { > > value 1; > > description > > "All data nodes SHOULD be included independent of > > any default values."; > > } > > enum trim { > > value 2; > > description > > "Data nodes that have a default defined and where > > the actual value is the default value SHOULD > > NOT be included."; > > } > > enum explicit { > > value 3; > > description > > "Data nodes that have a default defined and where > > the actual value is the default value SHOULD NOT be > > included. However, if the actual value was set by > > a NETCONF client or other management application > > by the way of an explicit management operation the > > data node SHOULD be included."; > > } > > } > > default trim; > > > > The draft is extremely server-centric, like most IETF standards, but this > > leaf is too server-centric to ignore. > > > > Consider the possibility that the source of the file is NOT a NETCONF > server. > > This data may not be known so the default of "trim" may not be correct. > > > > IMO this leaf is noise because any tool that knows the schema will also > > know the YANG defaults. The solution is incomplete anyway because > > the presence of a leaf that has a YANG default is not enough. > > The "report-all-tagged" mode must be used to identify defaults. > > IMO this leaf should be removed, but at least add an enum called "unknown". > > > > > > Andy > > > > > >
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