Subject: RE: [Simple] Tuple design team discussion summary

From: "Rosen, Brian" <[email-masked]>
Date: Tue, 15 Jul 2003 07:40:21 -0400

For this purpose, a service is a tuple representing a communications
path to a set of devices that have some common characteristics. 
The tuple contains the URI to the service, and the characteristics
(capabilities)
of the service.
 
The service endeavors to deliver a request for communication to an
appropriate
device from the set of devices it controls.  The presence information
presented by the service is represents that of the service as a whole,
rather than that of one of its constituent devices.  It is NOT
necessarily a simple pivot of device presence information.  The service
may have additional information, and it may combine information in
ways not expressible as a pivot of the device data.

A service is differentiated from a device in that the URI explicitly
represents the services, requests for communication will be forwarded
to one of the devices the service controls. 

A service is differentiated from a user in that a user may have
multiple services, each of which may have separate presence tuples.
Normally, a user has a single tuple representing the presence of
the user as a person.

You can think of this as a hierarchy, where a user has a set of
services each of which has a set of devices.  Nothing limits
the hierarchy to two levels (a service could aggregate multiple
services, although I can't think of an example that makes a lot
of sense).  It's also possible to have a user who doesn't have
services.  In that case he has a set of devices that are aggregated
directly to form the user tuple.  The service is equal to device.

Brian

> -----Original Message-----
> From: Henning Schulzrinne [mailto:[email-masked]]
> Sent: Tuesday, July 15, 2003 7:05 AM
> To: [email-masked]
> Cc: [email-masked]; [email-masked]; 
> [email-masked]
> Subject: Re: [Simple] Tuple design team discussion summary
> 
> 
> [email-masked] wrote:
> 
> > I agree with Brian. I think we only ever discussed those 3: device,
> > service and user. We don't need to be very explicit, information in
> > the tuple give away the finer details about that thing that 
> the tuple
> > represents.
> > 
> > Other than those 3, I haven't heard of other things that a tuple can
> > represent, unless we allow a combination of the 3 above (which I
> > believe we don't).
> 
> To beat a horse carcass: While device and 'user' has reasonable 
> definitions, nobody, after a year+, has provided an operational 
> definition of service. Since this label needs to be understandable by 
> people who have not participated in the Tuple Theory 745 
> class (this is 
> graduate-level stuff...), I don't think an elaborate definition helps.
> 
> 'device', 'user' and 'other' seem to work ok, which seems to be close 
> enough. (Earlier versions of RPIDS had an approximation to such an 
> element, with the addition of 'group'.) For those, there are 
> reasonable 
> pictograms, too - phone, stick person and ?.
> 
> Henning
> 
> 
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---

From: Henning Schulzrinne <[email-masked]>
Date: Tue, 15 Jul 2003 14:20:51 -0400

In short, service = collection of devices

The 'common characteristic' is sufficiently vague that I'm not sure it 
is helpful. After all, you could presumably have a service that is 
simply the enumeration of all characteristics (say, if you combine all 
your Microsoft-supplied devices).

With this definition, I think this labeling is at least conceptually 
complete:

(1) one tuple (or relationship with multiple) = presentity,

(2) several tuples fronting for more than one device each = service,

(3) any number of devices that are not divisible.

Presumably, labeling a single tuple as a presentity rather than a 
service implies that the presentity is complete - all devices are 
reachable through that. A presence document with just one 'service' 
tuple implies that there might be others which got filtered along the way.

I'll add it to the draft.

---

From: Henning Schulzrinne <[email-masked]>
Date: Tue, 15 Jul 2003 14:20:51 -0400