Semantic Model Mail Archive: SM> RE: IPP> 4 significant p

Semantic Model Mail Archive: SM> RE: IPP> 4 significant p

SM> RE: IPP> 4 significant proposed increases in conformance requirem ents for the IPP Document object spec

From: McDonald, Ira (
Date: Fri Apr 18 2003 - 14:34:17 EDT

  • Next message: McDonald, Ira: "RE: SM> Re: IPP> 4 significant proposed increases in conformance requirements for the IPP Document object spec"

    Hi Michael,

    Tom's notes are actually incomplete. A conforming implementation
    MUST support at least one scheme (I suggested we RECOMMEND that
    'http:'), but an administrator _at_run_time_ may choose to disable
    this feature by reconfiguring "reference-uri-schemes-supported".

    I proposed making this operation (Send-URI) mandatory. But only
    if ALL implementations MUST support at least one reference scheme
    and SHOULD support 'http:' (note that PSI servers MUST support
    'http:' for the AddDocumentByReference method).

    I contend that the burden of adding a minimal HTTP client to an
    existing IPP-based printer is minimal. That's the question.

    - Ira McDonald

    -----Original Message-----
    From: Michael Sweet []
    Sent: Friday, April 18, 2003 6:50 AM
    To: Hastings, Tom N
    Subject: Re: IPP> 4 significant proposed increases in conformance
    requirements for the IPP Document object spec

    [My initial comments; I still haven't finished going through the
    document object spec, so I may have more comments early next week]

    Hastings, Tom N wrote:
    > ...
    > 1. Change the Send-URI operation and the corresponding
    > "reference-uri-schemes-supported" (1setOf uriScheme) Printer
    > Description attribute from OPTIONAL to REQUIRED for a Printer to
    > support. We agreed that a conforming implementation MAY have an
    > empty list for the "reference-uri-schemes-supported" Printer
    > Description attribute.

    So in essense you are just changing the status code from
    server-error-operation-not-supported to

    > Reason: PSI requires this operation (and has no OPTIONAL
    > attributes). Optional operations are much less likely to get support
    > by clients. It is best practice for an OPTIONAL extension
    > specification (such as this spec) to have no OPTIONAL operations, so
    > that user clients will receive the same level of service from all
    > Printer implementations that support this extension.

    This reasoning makes no sense since you are also saying that
    "reference-uri-schemes-supported" can be an empty list, which
    means that you still have no service from an implementation that
    doesn't really support Send-URI.

    Also, I still question the usefulness of Send-URI and Print-URI
    since security issues (authentication and access control) make
    implementation for non-trivial URIs difficult, if not impossible.

    > 2. Change the Set-Document-Attributes operation from OPTIIOAL to
    > REQUIRED for a Printer to support.

    OK, however I think the state <-> status table (table 5) isn't
    right - what if you want to restart a job but print only 1
    copy of the first document?

    > 3. Change the Set-Job-Attributes operation from OPTIONAL to
    > RECOMMENDED for a Printer to support.
    > Reason: To go along with the change in the conformance requirements
    > for the Set-Document-Attributes operation. However, don't REQUIRE
    > Set-Job-Attributes, since most of the interesting attributes are
    > document attributes, not job attributes.

    Hmm, I'll have to review the current spec some more, but I don't
    remember a section on Set-Job-Attributes in the March 24th draft.

    Any chance you can post a message to the *IPP* list whenever you
    put a new draft up please? Also, it might be helpful to know when
    you plan on doing telecons - it can be difficult to schedule the
    time, but I *do* attend them occasionally...

    (I didn't get messages about either on the IPP list)

    > 4. Add an OPTIONAL 'guaranteed" value (see [ippsave] section 8.1) for
    > the "pdl-overrides-supported" Printer Description attribute (REQUIRED
    > in [rfc2911] section 4.4.28) to augment 'not-attempted', and
    > 'attempted' values. Also add a REQUIRED
    > ...

    OK, no problem with this.

    Michael Sweet, Easy Software Products           mike at easysw dot com
    Printing Software for UNIX             

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