MFD> Comments and questions on 20090112 Scan Model Doc

MFD> Comments and questions on 20090112 Scan Model Doc

MFD> Comments and questions on 20090112 Scan Model Doc

William A Wagner wamwagner at comcast.net
Wed Jan 21 15:46:28 EST 2009


Ira et al,

You make the point well that there are various not necessarily consistent
models in existence. It behooves the MFD group to decide what states should
be in the MFD model and to ensure that these states and state transitions
are well defined and consistent. Right now, I do not think that we have done
that for Scan Service. And I am having trouble coming up with a overall MFD
generalization based on the Scan Service Model.

Thanks,

Bill Wagner



-----Original Message-----
From: owner-mfd at pwg.org [mailto:owner-mfd at pwg.org] On Behalf Of Ira McDonald
Sent: Wednesday, January 21, 2009 3:16 PM
To: William A Wagner; Ira McDonald
Cc: mfd at pwg.org
Subject: Re: MFD> Comments and questions on 20090112 Scan Model Doc

Hi Bill,

IPP Admin Ops (RFC 3998) clearly defines the behavior of
ShutdownPrinter and StartupPrinter on page 14:

"3.5.2.  Shutdown-Printer Operation

   This OPTIONAL operation allows a client to shutdown a Printer; i.e.,
   to stop processing jobs without losing any jobs and to make the
   Printer object unavailable for any operations using the IPP protocol.
   There is no way to bring the instance of the Printer object back to
   being used, except for the Startup-Printer (see section 3.5.3), which
   starts up a new instance of the Printer object for hosted
   implementations."

DPA Admin Ops (ISO 10175-Part3) defines ShutdownPrinter to
place the Printer object in the "shutdown" state (NOT "idle" or
"stopped") but to NOT delete the Printer object.  It also defines
DeletePrinter for deleting the object and discusses but does
NOT define RestartPrinter - Palladium did RestartPrinter as a
DPA Control operation (the DPA wildcard admin op) I believe.

If, like DPA, you postulate that operations like StartupPrinter
(in RFC 3998) and CreatePrinter (in DPA) are actually targeted
at a System (IPP, WIMS, SM/2.0) or Server (DPA) object, then
it's perfectly reasonable to let RestartPrinter restart an inactive
Printer from the "shutdown" state.

Note that DPA does NOT define "printer-state-reasons".
DPA defines ONLY "printer-state" with enumerated values:

  unknown, idle, printing, needs-attention, paused, shutdown,
  job-start-wait, job-end-wait, job-password-wait,
  needs-key-operator, connecting-to-printer, timed-out

DPA "shutdown" looks like IETF Host MIB "down" to me.

Note that the basic reasons for IPP "stopped" are first-class
states in DPA.  There's clearly more to services than the
three IPP states.

Comments?

Cheers,
- Ira

Ira McDonald (Musician / Software Architect)
Chair - Linux Foundation Open Printing WG
Blue Roof Music/High North Inc
email: blueroofmusic at gmail.com
winter:
  579 Park Place  Saline, MI  48176
  734-944-0094
summer:
  PO Box 221  Grand Marais, MI 49839
  906-494-2434



On Tue, Jan 20, 2009 at 2:54 PM, William A Wagner <wamwagner at comcast.net>
wrote:
> Ira,
>
> Thanks for your explanation.
>
> BTW I did not suggest that Down and Testing were reasonably substates of
> IDLE, but that they could be considered substates of STOPPED or, from an
> external viewpoint, equivalent to UNKNOWN if the state cannot be
> communicated.
>
> Since, from my understanding, IPP is the model of the Print service of an
> MFD, defining a different state set for other MFD Services makes it
> difficult to have a consistent approach to modeling MFD services. However,
> if, as you suggest, we are committed to consider TESTING and DOWN as
primary
> states of a Service, I think we need to better deal with how these states
> are entered and exited.
>
> I do not see in the document the information that ShutdownService shuts
down
> but does NOT end that service instance (it may be inferred from Fig 26,
but
> it is counterintuitive). I see no mention of a DeleteService operation or
> action (although I agree that if ShutdownService does not end that service
> instance, something should.) As I have indicated, I can find no
> identification of a RestartService operation, or other explanation how
this
> action is effected. I can find no explanation of how a Service is put into
a
> TESTING state nor (without Restart) how it transitions to anything except
> DOWN.
>
> Models are approximations or idealized views, and I think that different
> models may be equally valid. But model descriptions should attempt to be
> consistent and complete within themselves. They should be well explained
and
> neither intuitive understanding nor inherent understanding of some
> unidentified standard should be assumed.
>
> It may not be appropriate to attempt to do this with the Scan Service at
> this time, but if we are to define models with consistent semantics, I
think
> we need to settle on and properly document the Service states and the
state
> transition actions. Para 7.1.5.10  of the Scan Service document does
present
> a transition model, but I suggest a better documentation of the transition
> actions is necessary.
>
> As always, opinions from others would be appreciated.
>
> Thanks,
>
> Bill Wagner
>
> -----Original Message-----
> From: owner-mfd at pwg.org [mailto:owner-mfd at pwg.org] On Behalf Of Ira
McDonald
> Sent: Tuesday, January 20, 2009 11:47 AM
> To: William A Wagner; Ira McDonald
> Cc: mfd at pwg.org
> Subject: Re: MFD> Comments and questions on 20090112 Scan Model Doc
>
> Hi Bill,
>
> Thanks for all your good comments on Scan Service.
>
> Here are my thoughts about service state.
>
> It's IPP that is deficient in primary states.
>
> DOWN is NOT some state-reason of IDLE.
> It is a primary state in CIM Services as well.
>
> By the same token, TESTING is a primary state.
> A service (or device) in TESTING MUST NOT
> execute any normal user jobs.
>
> The stupidly deficient IPP states are the wrong
> model to follow here, because mapping to CIM
> and other interfaces will become convoluted and
> fragile (i.e., implementation mappings will vary)
> - behavior of operations would depend on the
> state-reasons and not the primary state.
>
> Lastly, the WIMS/1.0 Protocol and Schema set
> (and more recent Semantic Model/2.0 schemas)
> have had this set of service states and their state
> transitions for five years - it's pretty late to change
> them, IMHO.
>
> StartupService instantiates a NEW service instance.
> ShutdownService shuts down but does NOT destroy
> that service instance.  RestartService is necessary
> to restart the previous service instance.
>
> These three admin operations are needed for every
> Imaging System service.  These operations are taken
> from ISO 10175-Part3 (DPA Admin), as are equivalent
> IPP operations in RFC 3998.
>
> DeleteService is probably also necessary (after a
> ShutdownService) to actually delete the inactive
> service object  It's specified in ISO 10175-Part 3, but
> was not included in RFC 3998 or WIMS/SM schema.
>
> BTW, while not exhaustive, the state transition tables
> at the end of ISO 10175-Part3 are informative here.
>
> Cheers,
> - Ira
>
> Ira McDonald (Musician / Software Architect)
> Chair - Linux Foundation Open Printing WG
> Blue Roof Music/High North Inc
> email: blueroofmusic at gmail.com
> winter:
>  579 Park Place  Saline, MI  48176
>  734-944-0094
> summer:
>  PO Box 221  Grand Marais, MI 49839
>  906-494-2434
>
>
>
> On Mon, Jan 19, 2009 at 11:05 PM, William A Wagner
> <wamwagner at comcast.net> wrote:
>> The following questions/comments are a result of my effort to generalize
> the
>> information for the overall MFD document. I acknowledge that the
questions
>> may be a result of my misunderstanding rather than an error or
> inconsistency
>> in the document. But that may suggest that some clarification may be
> useful.
>>
>>
>>
>> Thanks.
>>
>>
>>
>> Bill Wagner
>>
>>
>>
>>
>>
>> 1.       Line 2172 refers to an administrative  RestartJob operation as
> does
>> Fig 33 and Fig 41. . No such operation is included under interfaces. As
>> described, it is unclear that a RestartScanJob has the same sense as the
> IPP
>> Restart-Job (restart a job that is  retained in the queue after
processing
>> has completed); indeed,  it is unclear how RestartScanJob could have the
>> same sense. Is there such an operation ?
>>
>>
>>
>> 2.       Line 1393 refers to Restart in the same context as Startup and
>> table 1403 refers to a RestartScanService operation. . Line 2166 refers
to
> a
>> generic Restart. Fig 26, Fig 33 refer to a restart(), presumably
>> RestartScanService. No such operation is included under Interfaces.
>>  Actually, I find the sentence starting "Otherwise, if the Scan Service
>> needs a ShutdownScanService() operation
" on line 2165, confusing.
>>
>>
>>
>> 3.       One of the service states is TESTING. Fig 26 indicates that only
>> way into testing is via a testing() request. No such request is
> identified.
>> Should we indicate that testing() represents one of possibly several
>> implementation dependent functions?
>>
>>
>>
>> 4.       In Fig 26, the only ways out of TESTING are shutdown() to DOWN
> and
>> restart(),  presumably RestartService,  to IDLE.  Again, is there a
>> RestartService operation? Also, this diagram does not show the transition
>> from  UNKNOWN (initialization phase) that is identified in Fig 25 to be
to
>> DOWN; indeed, there is no entry to Fig 26.  The Scan Service Theory of
>> operation suggests that testing may take place in (or from) the
>> Initialization phase (which right now only includes the UNKNOWN state.)
> The
>> reference is the HR MIB statuses; but the draft does not cover the other
> HR
>> defined statuses of RUNNING and WARNING. Does it make sense to mix IPP
>> states with HR Device statuses? Do we really want to try to standardize
>> Service startup and testing? I  realize that this  is a bit late in the
> game
>> to bring up, but in considering the MFD overall case,  adapting the  IPP
>> approach of just three Service states:  Idle, Processing, and Stopped
> (along
>> with an inherent Unknown) would seem adequate.  If the Service is
> reporting
>> states, "Down" and "Testing" are variations of the Stopped state covered
> by
>> state-reasons; if the Service is not reporting state (i.e., is
effectively
>>  "Unknown" as far as the rest of the world)  then the transitions and
>> intermediate states can be considered implementation dependent. I
> recognize
>> that this would affect 7.1.5.10. ( It would also address most of the
> issues
>> above.)
>>
>>
>>
>> 5.       Line 1077 and subsequent. I do not understand the reference to
> §6.
>> (Console is discussed in para 2.2.12 of RFC3805)
>>
>>
>>
>> 6.       Line 1084 . Cover is not defined in RFC3805 except as part of
>> General Printer. I suggest the reference be dropped.
>>
>>
>>
>> 7.       Line 1122; OutputChannelDefaultJobControlLanguage has a type
>> interpreter?
>>
>>
>>
>> 8.       Line 1127; OutputChannelInterface has a type interface
>>
>>
>>
>> 9.       Line 1107; Interpreter is listed as not applicable to Scan
> Service.
>> What subunit does formatting of the digital document?
>>
>>
>>
>>
>
>





More information about the Mfd mailing list