IFX Mail Archive: RE: IFX> Using CONNEG with IPPFAX

IFX Mail Archive: RE: IFX> Using CONNEG with IPPFAX

RE: IFX> Using CONNEG with IPPFAX

From: McDonald, Ira (imcdonald@sharplabs.com)
Date: Wed Jan 30 2002 - 12:30:45 EST

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    Hi John,

    I don't like using the 'hash-based' approach, because it completely
    sacrifices human readability (the whole benefit of CONNEG, in my
    opinion).

    I think we should explore the possibility of explicitly excluding
    'resolution' and a few other frequent variables from our base
    CONNEG profiles.

    Otherwise, yes I'd prefer to return to full CONNEG expressions with
    all variables.

    Cheers,
    - Ira McDonald
      High North Inc

    -----Original Message-----
    From: John Pulera [mailto:jpulera@minolta-mil.com]
    Sent: Tuesday, January 29, 2002 7:25 PM
    To: IPP-Fax Group
    Subject: IFX> Using CONNEG with IPPFAX

    Per my action item from the last meeting, I checked with Graham Klyne (main
    author of the CONNEG-related RFCs) on the syntactical validity of section
    A.1.2 and its subsections in the UIF Specification. Although we'll be able
    to define "auxiliary predicate" values (e.g., "profile-uif-f" or
    "profile-uif-cg"), we won't be able to use them to add on incremental
    features like the following:
     
    (| (profile-uif-s)
       (& (profile-uif-f])
           (dpi=[200,300,600,1200]) )
       (& (profile-uif-c)
           (dpi=[200,300,600]) ) )
     
    to indicate optional support of 1200 dpi for UIF Profile F and optional 600
    dpi for UIF Profile C. He made a couple of suggestions:
     
    (1) If the goal is to shorten the length of the CONNEG expression, then he
    suggested we use the hash-based approach described in RFC2938 (for which
    there is a freely available Java implementation at the IMC website:
    http://www.imc.org/ietf-medfree/index.html). The disadvantage here, however,
    is capabilities advertised in the CONNEG expressions would no longer be
    "human-readable". See some examples here:
     
    (2) If human readability is desired, then, alternatively, we can exclude
    frequently varied parameters (e.g., resolution) from the minimum CONNEG
    strings specified in section A.1.2.1 of the UIF spec. If we did this, then
    the CONNEG expression shown earlier would be valid. But, in this case, how
    many parameters should be excluded from the minimum CONNEG strings &
    separately specified in the CONNEG expression? Where would we draw the line?
     
    Do I here preferences for either alternatives 1 or 2? Or should we just go
    back to using the whole expression since we've already taken into account
    really long values for the 'uif-profile-capabilities' IPP attribute by using
    1setOf text(MAX)?
     
    Graham Klyne's response is attached.
     
     
    John P



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