- From: Rudolf J Streif <rudolf.streif@ibeeto.com>
- Date: Tue, 20 Aug 2019 14:01:24 -0700
- To: "Winzell, Peter" <peter.winzell@volvocars.com>, "ted@w3.org" <ted@w3.org>, Peter Winzell <peter.winzell@jayway.com>, public-automotive <public-automotive@w3.org>
- Message-ID: <2d9ffd41-1a3a-ef46-8cbd-ac286b19d1d7@ibeeto.com>
Hi Peter, As you say there are a couple of possible locations where the hash can be calculated: * Client: that could be done with a client lib to hide that process from the developer which is desirable * Server: as you say, if the length of the path is more than 3 elements the server calculates the hash * Proxy: all requests are sent to a proxy server that computes the hashes Since I have not deployed ViWi and don't know what the reason for the limitation is I cannot tell what the best method would be (and most likely there's no one-fits-all solution). :rjs On 8/20/19 1:52 PM, Winzell, Peter wrote: > Hi interesting, So that would keep the VSS model and we would have URIs like Vehicle/256Hash(x.y.z.w.u)/vssleaf_i > So, then the server would keep a table of the hashed branch which would generate x.y.z.w.u construct the correct treepath down to the leaf as in this example…and through its internal data table match the branch with the actual vehicle signal and return the response. So, hiding the actual hash compute from the 3party developer we can do with a client API, or we need to add it somehow to the VIWI protocol( if long ass tree branch in request try hash else return some error) ? What are your thoughts there? > > Br > Peter Winzell > > > > > On 8/20/19, 1:26 PM, "Rudolf J Streif" <rudolf.streif@ibeeto.com> wrote: > > Out of curiosity: what is the reason of the tree depth limit to 3 for > ViWi? Is that a technical limitation of some sorts? > > The reason for VSS's essentially unlimited tree structure is > extensibility. The tree can grow horizontally and vertically as needed. > When we created VSS we found this very useful. We purposely tried to > avoid any limitations. > > Another way of possibly overcoming the tree depth limitation and > potentially providing a more automated way of mapping is to use hashes > for the branches of the tree that are omitted. So for Peter's example: > > To replace > > Vehicle.Cabin.Seat.Row4.Pos1.Isbelted > > with a SHA256 > > /Vehicle/103890db1712299c242c7613e0195d56bd99155dab18e1ad1477a152b2ab3337/Isbelted > > Obviously this is not human-readable anymore and since SHA256 is a > one-way function the REST server can only do a comparison to check for > the resource but that comparison is rather quick. A lookup table for > reverse lookup could easily be created with the VSS processors. > > :rjs > > On 8/20/19 9:59 AM, Winzell, Peter wrote: > > Hi Ted, > > So, could this alternate URI be exemplified ? As this would keep the VSS model intact? > > > > Br > > Peter Winzell > > > > > > > > On 8/20/19, 5:22 AM, "Ted Guild" <ted@w3.org> wrote: > > > > Regarding tree depth, one idea is to support alternate URIs so you can > > have paths that correspond to tree branches and for those to either > > transparently proxy or redirect. > > > > We remain extremely focused on vehicle signals, they are of greater > > interest for more participants than the other 'domains' we'll want to > > have in-vehicle services for. We want the protocol to be able to be > > able to accommodate them as well. > > > > On Mon, 2019-08-19 at 15:58 -0700, Peter Winzell wrote: > > > Hi All! > > > Some thoughts for tomorrows’ meeting. Looking at the VIWI submission > > > and the VIWI data model and how to keep VSS intact. > > > For me it seems that the we would try to map the VSS data model > > > against the viwi.service.car definition. > > > > > > In VIWI we have a number of vehicle data objects defined such as > > > car/info. infoObjects where we are able to retrieve the VIN is one > > > such object: > > > > > > /car/info/<vinidentifier> > > > > > > In VSS: > > > Vehicle.VehicleIdentification.VIN > > > > > > In Vss the vin number is defined as the tree branch > > > Vehicle.VehicleIdentification.VIN > > > > > > Vehicle — | > > > —| > > > VehicleIndentification —| > > > VIN > > > —| > > > … > > > … > > > > > > In this case we have two tree structures with the depth 3. This > > > seems to match pretty well ? > > > > > > However, VIWI limits the depth of the tree structure to 3 , which in > > > the following example makes VSS incompatible with the current VIWI > > > data model : > > > > > > In VSS: > > > Vehicle.Cabin.Seat.Row4.Pos1.Isbelted. > > > > > > In this case we would try to match this we would have to define 3 > > > more vehicle data objects: > > > /Vehicle/Cabin/Seat > > > - available seat objects would be returned by a GET > > > request, row would be one such object which links to the > > > /Vehicle/Row/Rowobjects > > > - available row objects returned by a GET request. Which > > > links to positionObjects > > > /Vehicle/Pos/Positionobjects > > > — Isbelted element > > > > > > This would keep the tree limit - in my view this would transform the > > > VSS data model into something not VSS although we have some sort of > > > mapping ?. The other way around is not possible since this would make > > > the current VIWI model incompatible with present in-vehicle > > > implementations if I understand correctly. So I now see us spitting > > > the spec into two separate tracks where we have VISS/VSS and VIWI > > > submitted as the W3C signal specification. I have a feeling that both > > > tracks will suffer from adapting to each other/ and in the end we > > > could end up with something of inferior technical quality. For Volvo > > > cars we see VSS as a key element to the W3C submission and we want to > > > continue this work going forward. > > > > > > Br > > > Peter Winzell > > > > > > > > > > > > > > > > > > > > > > > > > > -- > > Ted Guild <ted@w3.org> > > W3C Automotive Lead > > http://www.w3.org > > > > > > > > >
Received on Tuesday, 20 August 2019 21:01:51 UTC