[Cloud] IPP Scan question.

[Cloud] IPP Scan question.

William A Wagner wamwagner at comcast.net
Thu Sep 25 18:15:14 UTC 2014


Thank you for your response.

1. I agree that Figure 3 of the MFD Scan spec definitely indicates that
there can be multiple images in one scan document; I do not see where it
indicates that there cannot be multiple documents is a job. Furthermore,
Figure 4 of that same document (with the associated text) definitely states
that, for a multi-document Job,  " Job object contains multiple Document
objects. Each Document can have a different set of processing parameters."
And further that the Scan Service semantic model may allow the End User to
specify a multi-document Job as a service output. If we have intentionally
decided to not consider multi-document jobs in IPP, that should be made
clear. I think it is to be determined if we decide to eliminate them from
the SM3. (Incidentally, I do not see a compelling Use Case for
multi-document Scan Jobs, although some may exist.)

2. I get your explanation that Get-Next-Document-Images refers to multiple
images of a document, and that "last-document" refers to the last image of a
document. But these are names are misleading. Do we use 'Images' to refer to
anything other than 'Document Images'?

I apologize for not commenting on the IPP Scan document earlier, but I think
the one document per job characteristic, despite what one might expect from
the names, should be made more clear. Also, as you suggest, the fact that
for Pull Scan,  the GetNextDocumentImages can redefine Compression Accepted
and Document Format Accepted for each image of potentially multiple images
Bill Wagner 

-----Original Message-----
From: Michael Sweet [mailto:msweet at apple.com] 
Sent: Thursday, September 25, 2014 9:12 AM
To: William A Wagner
Cc: Zehler, Peter; ipp at pwg.org; cloud at pwg.org
Subject: Re: IPP Scan question.


> On Sep 21, 2014, at 9:50 AM, William A Wagner <wamwagner at comcast.net>
> ...
> It is also clear from the IPP Scan specification GetNextDocumentImages
operation that a scan job can have multiple documents.

I don't think these are multiple document objects, however.
Get-Next-Document-Images is a convenient way to pull one or more
images/pages from the scanner, but from the point of view of the model they
are part of one document object and would be delivered (in the case of push
scan) as a single file.
> The Cloud conference call comment is that  FetchJob (corresponding to 
> Destination,  DestinationAccesses, and  InputElements for Scan with no
need to have a FetchDocument operation.  This  suggests that there is but
one document (possibly with multiple destinations) in a Scan Job.
Alternatively,  it may be that the Input Parameters and Destinations for
each one of multiple documents are defined in the CreateJob.  This seemes
inconsistent with the general Imaging Service model.

In the case of Scan, the CreateScanJob operation is instantiating a single
scan job containing a single document object that may have multiple digital
representations (e.g. PDF, TIFF, etc.) of the same images.  Figure 3 on page
22 of the MFD Scan spec seems pretty clear on that point.  This is similar
to how the Copy and FaxIn services work (single document jobs).

Print, FaxOut, and Transform can support multiple digital document inputs
(and thus multiple document objects).

I think the only inconsistency here is that some job services support
multiple document objects and some don't.  But I don't think that hurts the
overall model - just something worth pointing out.

(and perhaps as well worth considering/mentioning that most Print and FaxOut
service implementations only support single document jobs...)

> The IPP Scan specification definitely refers to multiple documents in one
scan job.  However, Figure 1 can be interpreted to mean that  the only
operation necessary for Scan is a CreateJob, with GetNextDocumentImages
necessary if it is a Pull Scan Job. Indeed, InputAttributes is defined to be
in the CreateJob request as well as are the Job Template attributes defining
destination; but it does not appear that different InputAttributes and/or
destinations can be specified for different documents.

I think the choice of reusing the "last-document" operation attribute in the
response of Get-Next-Document-Images operation is causing confusion here. It
really is (semantically) "last-document-image".

Pete, do you think this is worth an editorial change before publication,
either the attribute name or the description ("indicating that the last
document IMAGE has been reached")?

> [Also,  Compression Accepted and Document Format Accepted are defined 
> in CreateJob, but also in GetNextDocumentImages for Pull Scans. Can it 
> be assumed that requests in GetNextDocumentImages takes precedence?]

I think this needs some clarification - you put those in Create-Job for a
Push Scan and in Get-Document-Images for a Pull Scan.
> Do I correctly understand that, although there may be multiple documents
in a scan job, they must all have the same InputAttributes and the same
destination(s)?  An alternate approach might have been to send  a
SetDocumentAttributes sent for each document to be scanned, which contained
the input parameters and destination for each specific document/image file;
that would have been consistent with the Model.

Currently you scan whatever is at the input source and send it to the
destination(s) or pull the images with Get-Next-Document-Images.  The only
way to break things up is to create multiple jobs and specify the number of
images for each job in the "input-images-to-transfer" member attribute.
> For Cloud, we need to decide whether we should reflect the Semantic Model
(with which we should bet be consistent) or the IPP Scan Binding. Or do we
need to change the semantic model?

The intent is that IPP Scan would update the SM definition of SM Scan, since
SM Scan doesn't deal with Pull Scan.
> Also, a few minor editorial comments/questions I had while looking up
> 1.                          Table 1 lists Get-Next-Document-Images and
refers to PWG 5100.SCAN.  I take it that this  means to have the
specification refer to itself, but it is confusing even if the proper number
is inserted. Better to refer to the internal paragraph.


> 2.                          Figure 1 refers to the operation as
GetNextDocumentImage rather than GetNextDocumentImages
> 3.                          In para 7.1.1, under Group 2: Job Template
Attributes is a reference to section  There is no such section
(should it be 8.2?)
> 4.                          Although the text makes a distinction between
Print Jobs and Scan Jobs, section refers to a Print Job.

Thanks for catching these!

Michael Sweet, Senior Printing System Engineer, PWG Chair

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