Subject: Re: IPP>PRO - Print by reference

From: JK Martin <[email-masked]>
Date: Thu, 29 May 1997 17:37:43 -0400 (EDT)

We also readily agree with Roger's belief that print-by-reference
should be considered a basic (ie, mandatory) requirement for IPP.

Our largest customer has already implemented *exactly* what Roger
has described as a motivating scenario for print-by-reference.

And, as Randy Turner has pointed out, we don't want to put users
in the position of having to first download the (potentially huge)
document just to be able to print it.

We are also very concerned that the ersatz "IPP Level 1" approach
(aka the Microsoft/HP Simple Web Printing proposal) explicitly
refrains from embracing this critical requirement.

This is Not Good.  We hope others on the list will address this
situation before we dig ourselves in deep with regard to inter-
operability issues surrounding implementations of "Level 1" and
"Level 2" for IPP clients and servers.

	...jay

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----- Begin Included Message -----

>From [email-masked] Thu May 29 14:11 EDT 1997
From: Roger K Debry <[email-masked]>
To: <[email-masked]>
Subject: IPP>PRO - Print by reference
Date: Thu, 29 May 1997 14:07:28 -0400

As I stated in yesterday's telecon, Print by reference is a
requirement for Network computers that have limited local
storage. I suggested that we discuss this in more detail at
the protocol meeting being held at Sun in a couple of weeks,
and that we establish a set of assumptions on what the key
objectives are for Print by Reference.  From yesterday's
call it was clear that we each have a different view of what
Print by Reference is for.

I have what I think is a very straightforward requirement and
it does not require anything very complex in IPP. Furthermore,
I believe that this represents a major printing application within
the enterprise. Finally, I don't think that Print by Reference is
Web Printing, and we should probably distinguish the two.
Printing Web pages introduces more complexity and gets
into a number of issues that I agree with Randy on --
we probably don't want to deal with these in version 1.0
of the protocol.

My objective is to meet the following requirement.  An enterprise
chooses to keep libraries of technical reports, procedures
manuals, policies,  etc.  that are in printable format, e.g. as
Postscript files. They want to make these accessible to anyone
within their organization (no security requirements).  As an
employee I want to get a particular report and print it.  I'd like to
be able to use my web browser (or other GUI) to locate the
document and then issue a print request, pointing to the document
that I just found.  The printer gets the file and prints it.

This eliminates the need for me to download the file (In the
NC case, I might not have the local storage necessary to hold
the file to be printed).

This would be ideal in industries like insurance, where the home
office keeps the library of current policies, forms, contracts, etc.,
and when a branch wants to print a copy of something it just
points the print request to it.

The same could apply to publicly available documents (such
as Internet-Drafts) on the Internet. The two conditions required
are that the document be in a standard printable format and that
the document be publicaly available.

Roger K deBry
Senior Techncial Staff Member
Architecture and Technology
IBM Printing Systems
email: [email-masked]
phone: 1-303-924-4080

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From: "Scott Lawrence" <[email-masked]>
Date: Fri, 30 May 1997 08:47:53 -0400

>>>>> "JK" == JK Martin <[email-masked]> writes:

JK> We also readily agree with Roger's belief that print-by-reference
JK> should be considered a basic (ie, mandatory) requirement for IPP.

  One objection that was raised to the use of HTTP as a 'transport'
  was that it might require substantial complexity.  In response, I
  among others pointed out that only the 'origin server' requirements
  of HTTP would apply.  If print-by-reference is a MUST, then most of
  the HTTP client requirements would be equally applicable.

  As I said before, I believe that specifying how this works if
  present is a very good idea, but I believe that whether or not to
  put this feature in any given product should be a choice left to the
  vendor.

  This strikes me as an easy feature to describe as a very small set
  of attributes which describe whether or not print-by-reference is
  supported and if so what identity the printer is configured to use
  and any network access restrictions it may have.

--
Scott Lawrence           EmWeb Embedded Server       <[email-masked]>
Agranat Systems, Inc.        Engineering            http://www.agranat.com/

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From: Larry Masinter <[email-masked]>
Date: Fri, 30 May 1997 09:57:10 PDT

The capability of being able to print-by-reference might
be thought of as similar to the capability to be able to
print any given media type. In fact, print-by-reference
might be implemented by sending, instead of
application/vnd.adobe.postscript or application/vnd.hp.pcl,
sending message/external-body.
>   and any network access restrictions it may have.

The difficult issue in print-by-reference is how the sender
supplies the credentials if any at all are required. There
is no single standard for identity in Internet protocols, and
there's no standard encapsulation of credentials.

Larry
-- 
http://www.parc.xerox.com/masinter

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From: "Scott Lawrence" <[email-masked]>
Date: Fri, 30 May 1997 14:16:13 -0400

>>>>> "LM" == Larry Masinter <[email-masked]> writes:

LM> The difficult issue in print-by-reference is how the sender
LM> supplies the credentials if any at all are required. There
LM> is no single standard for identity in Internet protocols, and
LM> there's no standard encapsulation of credentials.

  Agreed; which, I presume, is why Roger K deBry [RKD] suggested that
  only 'publicly available' [a question-begging term, IMHO] documents
  could be printed by reference:

RKD> The two conditions required are that the document be in a
RKD> standard printable format and that the document be publicaly
RKD> available.

  My answer is to say that no credentials of the user are employed by
  the printer to obtain the referenced document; instead, whatever
  credentials of its own the printer has are used.  This degenerates
  to Rogers' model when the printer has no credentials of any kind
  (but note that the document repository might choose to consider the
  source IP address or domain name of the printer to be a form of weak
  but acceptable credential).  You might need an extra status or two
  to communicate the inability of the printer to access the referenced
  document, but I suspect you need that no matter how you do this.