Re: [WoT-IG]: Comments on proposed charter for WoT WG

> On 2 Apr 2016, at 20:33, Kovatsch, Matthias <matthias.kovatsch@siemens.com> wrote:
> 
> To identify individual data points, there is always a combination of data element addressing ("paths") and hierarchy within this element ("arrays", objects). This not only differs from protocol to protocol, but often also from application to application. Using URIs together with something Schema-like to describe (hierarchical) payloads, we can easily describe and handle this in WoT. The protocol binding then maps this accordingly to the specifics of protocol and serialization. Where exactly the addressing information goes (protocol address or payload) depends on the protocol.
> 
> Defining URIs for every thinkable protocol is impossible, hence any definition of a new URI scheme is out of scope. Furthermore, this work needs to be done within the IETF, preferably by or with representatives of the body responsible for the protocol (Bluetooth SIG, OASIS, IETF WGs, ...). In the WoT WG, we should only define the mechanisms around URIs (to access data elements of things, which is in addition to the URI usage in RDF) and flexible protocol mappings to enable extensions now (in parallel to the W3C WG) and in the future. If we need something now, there is nothing stopping the individuals of the WG taking care of this work in the corresponding body.
> 
> I don't think we need a test for resourcefulness---anything can be a resource by definition anyway... I think the problem with the statement is that it considers that URIs for resourceful/RESTful protocols already exist. The point is, we do not define any new URI schemes in the WoT WG. We just support every protocol that has one, now or in the future.
> 
> Whoever is in favor of a particular protocol should implement it for the Plugfest and try to interoperate. They can also draft new URI schemes for that, which will be useful input for an I-D. This is the only way to figure out the details of the mappings and which adjustments to the WoT mechanisms might be needed to make it all work together. Keeping this at a fuzzy theoretical level will get us nowhere...
> 
> Is the idea getting clearer?
> Do you agree with that?


The point about having an out of scope section is mainly to assist companies with their IPR review of the potential patent licensing commitments in respect to the W3C Recommendations produced by a given working group. I would propose we drop this bullet point from the charter as it is proving complex to explain and justify. 

The nearest precedent I could find relates to XPath and XPointer. W3C defined a registry for XPointer Scheme Names, for use in URI fragments, see [1].  The URI specification is owned by the IETF and defines a generic syntax for URI fragments, but the meaning of these fragments is dependent on the resource identified by the URI, e.g. whether it is HTML, XML, etc. There has been some work done on an analog of XPath for JSON, e.g. Stefan Goessner’s JSONPath, see [2]. However, as far as I am aware, there is no official standard for that. RFC690 defines a less powerful approach called JSON Pointer, see [3], which may be good enough for most purposes.

Let’s leave the question of whether it is appropriate to define new URI addressing schemes to the experts for that protocol!


[1] https://www.w3.org/2005/04/xpointer-policy <https://www.w3.org/2005/04/xpointer-policy>
[2] http://goessner.net/articles/JsonPath/ <http://goessner.net/articles/JsonPath/>
[3] https://tools.ietf.org/html/rfc6901 <https://tools.ietf.org/html/rfc6901>
—
   Dave Raggett <dsr@w3.org <mailto:dsr@w3.org>>