[IPP] Models

[IPP] Models

[IPP] Models

William A Wagner wamwagner at comcast.net
Fri Jan 10 17:02:00 UTC 2014



The configuration of an " IPP Printer" being composed of an IPP Server and a
Print Service follows the diagram in IPP SIX and, indeed, goes back to RFC
2911.  Furthermore, the "output device" was not considered part of the IPP
Printer. We did not necessarily adhere to this configuration in the MFD
model where we defined the Device as representing the hardware implementing
the Service, prompting two distinct uses of the word "device". I think the
point of separating the IPP Server and the Print Service  was that IPP just
defines the IPP interface to the IPP Printer but does not define the form or
specifics of the Print Service (one could argue that the Semantic Model
does). But the separation is convenient in considering IPP  multifunction so
that, as you suggest, there is a common IPP front end to potentially
multiple imaging services.


I am inclined, in the SM3 document, to eliminate the <service> term in
defining operations (e.g., Create<service>Job), unless they are
service-type specific. The understanding would be that the specific service
is in the address.  What is your opinion in this?



Bill Wagner


From: Zehler, Peter [mailto:Peter.Zehler at xerox.com] 
Sent: Friday, January 10, 2014 9:06 AM
To: William A Wagner; ipp at pwg.org; 'Semantic Model 3.0 Workgroup discussion
Subject: RE: [IPP] Models




I'm a little confused on what you have labeled as an IPP Server and IPP
Printer.  My view is that an IPP Server is what you have labeled as IPP
Printer.  It contains the required protocol stacks, resources and service
instances.  I have always understood an IPP Printer to be an instance of a
Print Service.  This would map to a Virtual Printer in ISO 10175 DPA.


I have assumed that there would be a single IPP stack implementation (i.e.,
IPP Server in your first diagram) that would front end the service
instances. Each service instance would be referenced by its unique URL
(e.g., same URI Scheme, hostname and port, different paths)  Implementers
are free to do things differently but I assume the intent of the IPP
specification would be to multiplex all the IPP Services over a single port
(i.e., 631)


I agree that we could have used generic verbs but once we finished print we
were stuck with the names of the verb.  Since IPP uses an enumeration we can
reuse the enumeration across the services.  In the semantic model the
operation does not really identify the service type.  The Service URL
identifies the service type.  The operation names are simply service
specific aliases for a common semantic operation.  We could have opted for a
generic name but we went with a naming convention instead.




Peter Zehler

Xerox Research Center Webster
Email: Peter.Zehler at Xerox.com
Voice: (585) 265-8755
FAX: (585) 265-7441
US Mail: Peter Zehler
Xerox Corp.
800 Phillips Rd.
M/S 128-25E
Webster NY, 14580-9701 



From: ipp-bounces at pwg.org [mailto:ipp-bounces at pwg.org] On Behalf Of William
A Wagner
Sent: Thursday, January 09, 2014 12:57 PM
To: ipp at pwg.org; 'Semantic Model 3.0 Workgroup discussion list'
Subject: [IPP] Models


I  am unclear on a Semantic Model configuration issue, which also may relate
to IPP multifunction. The Semantic Model assumes that  communication is from
client to service.  But in our operations, we identify the Service (e.g.,
CancelFaxInJob), which should not be necessary if the operation is directed
to the service.  On the other hand, depending  upon where you want to put
the transport address boundary, it is reasonable to think of operations
being directed to the MFD, which corresponds to the System, in which case
the service should be identified. Of course, this is inadequate if there are
multiple services of a given type in the same system. Bottom line, should
operations identify the Service type?


With respect to IPP, should the multi service configuration look like A or B
below? (or perhaps something else entirely?) Again, the modeling question is
whether the service  identification is included in the operation.

IPP Printer A.jpgIPP Printer B.jpg

IPP Multifunction A
IPP Multifunction B



Bill Wagner



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