Re: [Geopriv] Long review of draft-ietf-geopriv-loc-filters-07

["James M. Polk" <jmpolk at cisco.com>]

Hannes

in-line below

At 06:29 PM 11/3/2009, Hannes Tschofenig wrote:
> Hi James,
>
> Thanks for your detailed review. I am in the process of updating it and have
> comments here and there.
>
> Here is one:
>
> Draft Text:
>
> --------
>
> <?xml version="1.0" encoding="UTF-8"?>
> <filter-set xmlns="urn:ietf:params:xml:ns:simple-filter">
>     <ns-bindings>
>         <ns-binding prefix="dyn"
>             urn="urn:ietf:params:xml:schema:pidf:dynamic"/>
>     </ns-bindings>
>     <filter id="123" uri="sip:presentity at example.com">
>         <trigger>
>             <changed by="3"> [<---James]
>               //dyn:speed
>             </changed>
>         </trigger>
>     </filter>
> </filter-set>
>
> ------
>
> [James]
>
> I get the XML,
> but I don't see what the speed now is of
> the device/target?
> What if this device is moving at 200kmph,
> where would that be placed in the XML?
> Of, is this left for the application at the
> subscriber to calculate?
> If the latter is true, something needs to be
> said about this expectation.
>
> ------
>
> The filter would not tell you what the current speed is.

ok, I get that now (though it isn't exactly stated this way explicitly).

Let me pose a scenario for you and see if there is just one NOTIFY or 
there are many:

Alice is the target.  Initially she isn't moving.  her device accepts 
a subscription with a <changed by="3"> element in it.  She starts to 
accelerate (linear or not) until se reaches 100mps.  How many NOTIFYs are sent?

1 because she crossed the by="3" attribute, or each time she 
accelerates more than 3mps faster since the last NOTIFY.

I'm guessing the latter, but want to be sure.

Again, this isn't exactly explicitly stated in the -07 rev.

James

BTW -- I think Alice sending a NOTIFY every time she accelerates or 
decelerates by="3" would be useful information, especially in the 
emergency case.

It's toobad we cannot have a "is moving" but less than by="3" 
indication.  This would tell us it is in a stationary position or 
not. Again, for a device/inventory tracking application, this would 
seem like very useful information to have.


> The current document only supports 'by' and hence you cannot say something
> like 'tell me when he goes faster than 100kmph'.
>
> Ciao
> Hannes
>
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