Smith,
When I say "The Service URL identifies the service type" I mean that the URL is the transport endpoint for s service instance. The path segment of the URL is not necessarily fixed for a service type. A URL such as <ipp://somemfd.example.com//ipp/appletree> could just as easily be an IPP Printer as it could be IPP Scan. The discovery protocols or directory entries would map the service instance to the URL. The most common deployment will probably be a single instance of a service for a server (e.g., an MFD offering a single print service, a single scan service and a single faxout service). I see no problem with various environments (e.g., WiFi Alliance, Mopria) mandating a best practice that would fix the path segment for the URL.
I had never thought about it before but the IPP model does not really have an service status attribute that self describes its service type. I would agree that it seems that inspection of the "ipp-features-supported" is the way that one knows what service "type" is at a particular resource path. (I had always assumed the Client would already know what type of service they require and would discover only those endpoints of the appropriate service type.)
Pete
Peter Zehler
Xerox Research Center Webster
Email: Peter.Zehler at Xerox.com<mailto: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 Kennedy, Smith (Wireless Architect)
Sent: Friday, January 10, 2014 12:20 PM
To: Zehler, Peter; William A Wagner; <ipp at pwg.org>; Semantic Model 3.0 Workgroup discussion list
Subject: Re: [IPP] Models
Greetings,
For what it is worth, Pete's description mirrors my own perception of the IPP object relationship. Graphically, this is how I understand the relationship between the "Printer objects" and the "server" to exist, at least in terms of IPP:
[cid:image001.png at 01CF0E03.55552D50]
Pete, when you say "The Service URL identifies the service type", do you mean that the resource path in a URL defines the service type? If so, I'm not sure that is guaranteed to be true. For instance "ipp://myhost.pwg.org/ipp/fax" could be "Fax" but could be anything. PWG 5100.15 says that an IPP FaxOut service MUST be at /ipp/fax but nothing prevents a single-function printer from having a conventional "Print" service at "/ipp/fax". It seems that inspection of the "ipp-features-supported" is the way that one knows what service "type" is at a particular resource path.
Smith
/**
Smith Kennedy
ATB Wireless Architect - PPS
Hewlett-Packard Co.
*/
On 2014-01-10, at 7:06 AM, Zehler, Peter <Peter.Zehler at xerox.com<mailto:Peter.Zehler at xerox.com>> wrote:
Bill,
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.
Pete
Peter Zehler
Xerox Research Center Webster
Email: Peter.Zehler at Xerox.com<mailto: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> [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<mailto: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.
<image001.jpg><image002.jpg>
IPP Multifunction A IPP Multifunction B
Thanks,
Bill Wagner
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