IPP Mail Archive: RE: IPP> New CUPS 1.1 beta and set-job-att

IPP Mail Archive: RE: IPP> New CUPS 1.1 beta and set-job-att

RE: IPP> New CUPS 1.1 beta and set-job-attributes extension [why not use "job-sheets"?]

From: McDonald, Ira (imcdonald@sharplabs.com)
Date: Tue Mar 21 2000 - 17:05:46 EST

  • Next message: Hastings, Tom N: "RE: IPP> New CUPS 1.1 beta and set-job-attributes extension [why not use "job-sheets"?]"

    Hi Jay,

    I don't think there is a white paper on 'collection' versus
    'object' pros and cons.

    I didn't mean to imply that the use for 'object' was to
    'absorb' something from ISO DPA. There has been some
    discussion on recent IPP Telecons about requirements to
    enhance IPP to comprehend fonts/forms/logos. And some
    concensus that it would be best done with a new 'Resource'
    container object.

    I do agree with Michael that exploring the development of
    new syntaxes (base datatypes) is often preferable for
    simplicity and robustness of implementation to the use of
    the 'collection' (bag of bits) syntax. I also think that
    when a new syntax won't do, real objects (like we are adding
    with the Subscription object) are also preferable to the
    use of 'collection'.

    I am dubious about the arguments that 'collection' can't
    simply have the WHOLE length of the 'collection' computed
    and inserted in the attribute. Device or clients that need the
    functionality that (purportedly) requires 'collection' are
    certainly capable of building the whole 'collection' in
    memory or on disk before sending it.

    And a whole lot of protocols that use ASN.1 encoding over
    the wire (LDAP and SNMP among them) decided that only
    'definite' encoding rules were legal - that is, they banned
    the ASN.1 use of 'here are some bits - watch for some flag
    octets to find the end of these bits' as not worth the
    bother.

    Of course, IPP gets most of its attributes and most of the
    semantics of its operations from ISO DPA. So it's a little
    late to shiver...

    Cheers,
    - Ira McDonald

    -----Original Message-----
    From: Jay Martin [mailto:jkm@underscore.com]
    Sent: Tuesday, March 21, 2000 5:19 AM
    To: IPP Mailing List
    Cc: McDonald, Ira
    Subject: Re: IPP> New CUPS 1.1 beta and set-job-attributes extension
    [why not use "job-sheets"?]

    Would someone be interested in presenting a *short* (and I mean SHORT) paper
    on the Pros and Cons of "Collections" vs. "Objects" with respect to IPP?

    It would appear Michael Sweet has some compelling arguments for his
    position,
    particularly given the product his company has produced. That is, when he
    says
    the current state of IPP makes it difficult (impossible?) to implement
    certain
    key capabilities, doesn't that raise a big flag?

    If someone has already published a short paper, please forgive me, and point
    me to the document in the archives.

    Thanks,

            ...jay

    PS: Keeping my long-held consistent view, "absorbing" anything from ISO DPA
    sends more than a modest shiver up my spine.

    "McDonald, Ira" wrote:
    >
    > Hi Michael,
    >
    > Thanks. You added a voice to mine (the one out in this
    > wilderness on recent IPP WG Telecons) saying that 'collections'
    > were not really a 'simple' extension.
    >
    > I have grave reservations about ANY future point version of
    > IPP making support for the 'collection' syntax mandatory.
    > Even with the latest 'legacy friendly' encoding proposals
    > from Bob Herriot (thanks Bob), I'm not a fan of 'collections'.
    >
    > In essence, 'collections' are 'poor man's objects'. I still
    > haven't heard the compelling case for why we wouldn't just
    > use REAL objects (for example 'Resource' object, in the ISO DPA
    > 'document resource' sense of fonts, forms, logos, etc.).
    >
    > Cheers,
    > - Ira McDonald, consulting architect at Sharp Labs America
    > High North Inc
    >
    > -----Original Message-----
    > From: Michael Sweet [mailto:mike@easysw.com]
    > Sent: Monday, March 20, 2000 7:33 PM
    > To: Hastings, Tom N
    > Cc: IPP Mailing List
    > Subject: Re: IPP> New CUPS 1.1 beta and set-job-attributes extension
    > [why not use "job-sheets"?]
    >
    > "Hastings, Tom N" wrote:
    > > ...
    > > Wouldn't it be simpler to use these values in CUPS, rather than
    > > introducing two new Job Template attributes?
    >
    > 1. The PPE uses COLLECTIONS for this stuff
    > 2. Collections are still being defined.
    > 3. CUPS currently does not do anything with collections (it will
    > store the raw data, but that is all)
    > 4. Without collections the job-sheets attribute cannot support
    > what CUPS needs to do.
    >
    > Given those things, it is unlikely in the EXTREME that we will
    > change our design this close to a final release.
    >
    > It is *possible* that we can change the names of the attributes
    > to "job-sheets-*", however I am concerned that we might step on
    > future attributes. Possible names:
    >
    > job-sheets-supported
    > job-sheets-start-default
    > job-sheets-end-default
    > job-sheets-start
    > job-sheets-end
    >
    > At least that would be in line with the IPP spec, but that also
    > means we must support "job-sheets" and "job-sheets-default". I'm
    > not sure how we would map that given the ambiguity in the spec...
    >
    > Another possibility might be to overload the "name" value to use
    > "start,end" for the "job-sheets" and "job-sheets-default" attributes,
    > however that might break clients that try to compare them against
    > the "job-sheets-supported" values.
    >
    > In any case, any change we make now CANNOT include support for the
    > PPE spec.
    >
    > --
    > ______________________________________________________________________
    > Michael Sweet, Easy Software Products mike@easysw.com
    > Printing Software for UNIX http://www.easysw.com



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