Re: [6tsch] minutes discussion models draft 1 October

"Romascanu, Dan (Dan)" <> Thu, 03 October 2013 08:40 UTC

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From: "Romascanu, Dan (Dan)" <>
To: "Pascal Thubert (pthubert)" <>, "" <>, Qin Wang <>
Thread-Topic: [6tsch] minutes discussion models draft 1 October
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Subject: Re: [6tsch] minutes discussion models draft 1 October
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Hi Pascal,

I *think* that it makes sense, but I would like to see text in a terminology section of the document defining the terms and providing references where relevant in order to make sure.



From: Pascal Thubert (pthubert) []
Sent: Wednesday, October 02, 2013 5:13 PM
To: Romascanu, Dan (Dan);; Qin Wang
Cc: Thomas Watteyne; 6TSCH
Subject: RE: [6tsch] minutes discussion models draft 1 October

Hello Dan;

I understand that we want to stick to RFC 3444 for Data and Information models. The limit to overcome is probably our understanding and practice of that specification.

In addition to the static representation, we have a need to discuss the dynamic view of the 6TiSCH operation and we are looking for appropriate terms.

At ISA100.11a this abstraction is often referred to as a "communication paradigm". Examples there are client-server, publish-subscribe and source-sink, which is a MP to MP distribution for alarms and alerts. We could reuse that terminology, with, in our case, the additions of classes for end-to-end (app layer), hop-by-hop (network layer) and one hop (Link layer) interactions.

It seems from the discussion that the applied model for a "communication paradigm" could be called an "interaction model".

For this particular draft, I'd then expect something like a Yang data model that can be trivially translated in CBOR for consumption by constrained devices.

Additionally, we would propose a layer 5 interaction model to transport that data. That interaction model would probably implement the client-server and eventually the source-sink paradigms with CoAP methods. But that would be an example not a limitation, since there can be other ways to transport that data, and other ways for format the bits and bytes.

Does that make sense?


From:<> [] On Behalf Of Romascanu, Dan (Dan)
Sent: mercredi 2 octobre 2013 13:07
To:<>; Qin Wang
Cc: Thomas Watteyne; 6TSCH
Subject: Re: [6tsch] minutes discussion models draft 1 October


I made this observation in the call yesterday. It would be good to use the terminology as defined in RFC 3444 in what concerns information models and data models. Information models define objects and the relation between them in a generic manner and are protocol neutral. Data models are less abstract, include implementation- and protocol-specific details, and are usually associated to data modeling languages. Using other terms, or worse - the same terms in a different manner - is confusing.

I suggest to add to the document a section of terminology which either points to RFC 3444, or describes the differences from what is described in 3444 and also explains other terms like 'interaction model'.



From:<> [] On Behalf Of Xavier Vilajosana Guillen
Sent: Tuesday, October 01, 2013 10:01 PM
To: Qin Wang
Cc: Thomas Watteyne; 6TSCH
Subject: Re: [6tsch] minutes discussion models draft 1 October

Hi Qin,

I agree with you .. URI is to indentify the resource, i.e how do we access a particular service offered by the management layer, I agree that this should have CoAP name on it if this is bound to URI. then the data model( the content of what we sent on the payload) this should be generic right?
so I see it in two separete things.
1-interaction model using CoAP
2-content/data model generic..


On Tue, Oct 1, 2013 at 11:56 AM, Qin Wang <<>> wrote:
Xavi and all,

When we talk about data model (DM), there are likely several points of view. For example:
(1) DM is a set of messages, their format, and the behavior caused by the messages.
(2) Besides (1), also includes the interface with specific protocol, e.g. URI in CoAP.

>From the point (1) of view, I agree Xavi. But, because URI is involved, so, it becomes CoAP Data Model.

So, can we separate the common part of DM, i.e. point (1) from protocol specific part of DM, i.e. something like URI?

What do you think?


On Wed, Oct 2, 2013 at 2:42 AM, Xavier Vilajosana Guillen <<>> wrote:
HI all,
I have a question raising from the minutes (sorry I could not connect today).
If title of the draft is "6TiSCH CoAP data Model" this means that in the future we will have "6TiSCH foo data Model". Is that the direction we want? Data Model is the way to represent message content (i.e what goes in the payload and is used by 6top commands). Why is this specific to CoAP?
Another aspect is interaction models, i.e message flows which in that case they are related to the capabilities of the transport mechanism.
just thoughts..  Sorry if I really go back to something you already discussed and it is really clear.

On Tue, Oct 1, 2013 at 11:22 AM, Thomas Watteyne <<>> wrote:

You will find the minutes of the discussion about the models draft from this morning at (also copy-pasted below).



Minutes Webex 1 October 2013, 6TiSCH group, models draft team

Note: timestamps in PDT.

Taking notes (using Etherpad)
1.    Thomas Watteyne
2.    Raghuram Sudhaakar
Present (alphabetically)
1.    Alaeddine Weslati
2.    Dan Romascanu
3.    Diego Dujovne
4.    Pascal Thubert
5.    Pouria Zand
6.    Qin Wang
7.    R. Nabati
8.    Raghuram Sudhaakar
9.    Thomas Watteyne
*         Present pre-draft ToC [Raghuram/Pouria]
*         Discuss ToC
*         Define contents of each section
*         [08.05] meeting starts.
*         Raghuram shares pre-draft through Webex
*         goals for today: define ToC, define contents of each section, pick title
*         Scope is to include data and interaction model for CoAP. At a later stage, extract information model as separate draft.
*         "6TiSCH data model" or "6TiSCH CoAP data model"?
*         [Thomas] personal opinion: have CoAP in title
*         [Qin] why interaction model on top of information model?
*         [Raghuram] we want to define message flows between PCE and nodes. Data model is exact definition of payload. We had rough consensus on using name-value pairs. Interaction model for CoAP or RSVP in future drafts. Interaction model provides abstract model of interaction between entities.
*         [Qin] RFC3444, interaction flows should be part of the data model? We should not conflict with RFC3444.
*         [Thomas] We may want to split the interaction from this (data model) draft.
*         [Qin] Data definition and coding is common part. For me, experience with different definitions. Don't want another terminology.
*         [Dan] Not extremely familiar with 6TiSCH but experience with data and information model. In the IETF, we have clear definitions about data and information model. RFC3444 accepted and used as reference. There are differences, i.e. interaction model. We need to stick with RFC3444 as close as possible.
*         [Raghuram] Goal of interaction model is try to extract information model at a later stage. CoAP is one of the transports we are using today, but we can use other protocol at a later stage. We can name it differently later "interaction method".
*         [Dan] If we are inventing a new name, it does not matter too much. We are looking at mapping different transports.
*         [Raghuram] Goal of interaction model is to extract the information model.
*         [Raghuram] Change to ToC: remove interaction?
*         [Thomas] Could be replaced by example scenarios.
*         [Pascal] We have identified interaction at L2, L3 and L5. We need to have discussion about the models.
*         [Raghuram] Conclusion: in ToC, new section 3.4 with "example interactions". Message formats would be moved up to 3.3, name-value pairs proposed.
*         [Thomas] Rough consensus?
*         [Qin] what's the different between management and informational resources?
*         [Raghuram] management resources are R/W, informational resources are R (e.g. DAGrank).
*         [Thomas] We could walk through ToC?
*         [Raghuram]
*         3.1 naming convention for URI schemes. For example, root resource "6t". Includes naming convention for resources under root resource.
*         3.2 resource of 6top we want to expose, i.e. management and informational resource.
*         3.2.4 user installed resources, e.g. subscribe for particular implementation.
*         [Raghuram] Should we have extensible resources?
*         [Thomas] Yes.
*         [Qin] What the functional description of a resource? Related to not only management but also informational resources. Should we put every description attached to every resource? Looking at the content, I can imagine a resource list, with a description for each one. Suggestion is to put description just following the resource list.
*         [Raghuram] Fine with that.
*         [Pouria] Other change "functional description of resources" will fold into 3.2.1 and 3.2.2.
*         [Raghuram] Resource is just the URI, linked to particular 6top variable. Methods would fall under description of resource.
*         [Qin] Description of the MIB?
*         [Raghuram] End-user should be able to get a specific parameters. Returned as name-value pairs. If an entity wants the entire MIB, we will have a separate resource.
*         [Thomas] Mapping of 6top commands included?
*         [Raghuram] Yes. Mapping of table of 6top commands presented in previous calls.
*         [Pouria] In resource management, information that can be written by PCE, or commands to be executed.
*         [Raghuram] Everything that change the TSCH schedule falls under the management resource.
*         [Raghuram] Section 4 will be moved up. A message format will be attached to each URI.
*         [Thomas] Map the attributes from minimal draft and the commands from 6top draft.
*         [Raghuram] That is the plan.
*         [Thomas] What are extensions?
*         [Raghuram] We don't want to define the URI for every attribute, we want to enable people to install a new resource with a definition.
*         [Raghuram] In that context, what are profiles?
*         [Thomas] Profile is overarching modification to basic behavior: e.g. adding resources or adding method to existing resource.
*         [Qin] Understanding about profile: resource is fixed, behavior of resource can be configurable.
*         [Pascal] +1 it's very important we are able to do add to basic behavior.
*         [Diego] How can we describe a trigger, e.g. number of measurements to average over.
*         [Thomas] Do we have a solution?
*         [Raghuram] Yes, complex triggers are defined using well-known formats. RFC already defines how to encode several thresholds. Output would be sent on CoAP response or observe notification. One generic method for any kind of trigger.
*         [Raghuram] In profiles, modify or add behavior. Add is easy. Profiles as a way to define extra sets of complex triggers. Discovery. What we could express as profiles are extra complex triggers.
*         [Thomas] What are the next steps?
*         [Raghuram] Updated version of draft by next week to discuss progress. Invite contributors.
*         [Thomas] Name of draft?
*         [Raghuram] What about "6TiSCH CoAP data model".
*         [Thomas] We need to know editor to create repository.
*         [Raghuram] AOB?

No other business raised.

*         [09.05] meeting ends.

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