This updated document includes agreements reached at the 7/14/99 IPP
telecon. I'll produce an updated version early next week for review
at our 7/28/99 telecon.
I've also copied these agreements to:
ftp://ftp.pwg.org/pub/pwg/ipp/proposed-registrations/operations/ipp-ops-admi
n-agreements-990716-rev.doc
ftp://ftp.pwg.org/pub/pwg/ipp/proposed-registrations/operations/ipp-ops-admi
n-agreements-990716-rev.pdf
ftp://ftp.pwg.org/pub/pwg/ipp/proposed-registrations/operations/ipp-ops-admi
n-agreements-990716.txt
Notes and Agreements on Admin operations, 7/16/99
From: Bob Herriot and Tom Hastings
Date: 07/16/1999
File: ipp-ops-admin-agreements-990716.doc
This updated document includes agreements reached at the 7/14/99 IPP
telecon. Agreements that have no comments indicate that the telecon
also agreed with the WG meeting.
Bob Herriot led the IPP review of the Additional Administrative
Operations document, dated June 30, 1999, at the 7/7/99-7/8/99 IETF IPP
WG meeting on Copenhagen. He generated the following notes and
agreements that were reached. The unnumbered issues are new issues
raised. The number issues refer to the numbered issues in the
specification. Unresolved ISSUES are highlighted like this in the .doc
and .pdf files.
The document being reviewed is available at:
ftp://ftp.pwg.org/pub/pwg/ipp/proposed-registrations/operations/ipp-ops-admi
n-990630.pdf
As always, these agreements are being sent to the IPP DL for further
discussion and final consensus.
1.ISSUE: What happens if the value for the from-operator-message for
job or printer is either a blank or an empty string for the set
operation or other operations that set this attribute?
Suggested resolution: If the operation attribute or the explicit
"printer-message-from-operator" (or "job-message-from-operator") is
supplied in the request, but with either a zero-length or white space
only content, it replaces the existing Printer or Job attribute as
expected. This is the way that the operation can indicate that there
is no longer a message from the operator for the Printer or Job
object. However, if the operation attribute or the explicit
"printer-message-from-operator" (or "job-message-from-operator") is
NOT supplied in the request, the corresponding Printer or Job
attribute is unchanged.
2. Printer and job operator message should also have a tick time, which
is required. Date-time value should be required if the printer
implements the current-date-time.
3. ISSUE: Can a client determine the values of "when" that are supported
for operations (Pause-Printer, Reset-Printer, and Shutdown-Printer)?
We did not resolve this issue, since there could be different values
of "when" for the three different operations. Adding three "when-
xxx" Printer Description attributes is a possibility, but does seem
overkill.
4. ISSUE 1: The 'after-current-job' value of the "when" operation
attribute must be supported.
5. ISSUE: In 13.1.5.8 server-error-printer-is-in-standby-mode, when
Printer has been shutdown in 'standby-mode' (as opposed to "shutdown-
function" = 'power-down'), : Restart-Printer and Get-Printer-
Attributes work, but does Set work?
Suggested resolution: We agreed that Restart-Printer and Get-
Printer-Attributes must work. We also agreed, that the purpose of
Shutdown-Printer to 'standby' mode, was long-term, not just a short
time to, say, change a Printer attribute or change a loaded medium.
However, on Restart-Printer (the next day), the operation or system
administrator might want to change some attributes before allowing
jobs to be submitted or already submitted jobs to be scheduled.
Therefore, we have the following issue:
ISSUE: What state the Printer comes back up on Restart-Printer and
how can the client control?
Possible alternatives:
a. Restart-Printer always brings the Printer up Disabled ("printer-
is-accepting-jobs" = 'false') and Paused ("printer-state" =
'stopped', and "printer-state-reasons" = 'paused'). Then the
operator issues Enable-Printer and Resume-Printer when want to
restore normal operation. The client can automatically issues these
operations depending on GUI options.
Advantages: This is the simplest to implement, allows new states to
be added without changing the Restart-Printer operation, and can have
the same GUI interface as b:
b. Add a REQUIRED operation attribute to Restart-Printer, something
like "printer-condition" with values: 'disabled-and-paused',
'enabled-and-paused', and 'enabled-and-idle'.
c. Have Restart-Printer restore the enable/disable and paused/idle
state to what it was when the Shutdown-Printer was issued. The
operation has to plan ahead at Shutdown-Printer time.
6. ISSUE: Perhaps only Restart should work when a printer is shut down,
not Get-Printer-Attributes?
Suggested resolution: We disagreed. Get-Printer-Attributes must
also work, so that a user can determine that the printer exists and
find out that is it shutdown, why, and/or when it might come back up
by querying the "printer-message-from-operator."
7. Tables for Set-Printer-Attributes and Set-Job-Attributes operations:
Change all occurrences of "MUST NOT if supported" to "MUST NOT"
8. In the tables that show what attributes are settable for Set-Printer-
Attributes and Set-Job-Attributes operations: should the table be
replaced with a list the attributes that are REQUIRED to be read-
only. Perhaps there is an attribute that lists all settable
attributes.
ISSUE: Can we add just one Printer Description attribute: "settable-
attributes" or do we need a "printer-settable-attributes" and a "job-
settable-attributes" Printer Description attributes? What if the
Interpreter and/or the Document object become real objects, would we
need to add "interpreter-settable-attributes" and "document-settable-
attributes" Printer Description attributes?
9. ISSUE: Do "operations-supported" and "versions-supported" reflect
software support or does the software examine the administratively
set values to determine behavior. That is, are they read-only or
read/write?
Suggested resolution: They are not included in the REQUIRED to be
read-only list in the spec. Therefore, implementer's are free to
make them either read-only, meaning that they reflect the
implementation and the client is unable to change via the protocol,
or may make them be read-write, meaning that the client can change
the behavior of the system using the protocol. In the latter case,
these attributes would be included in the new "printer-settable-
attributes" Printer Description attribute.
In order to allow the client to determine the values for the settable
attributes that are supported by the implementation, as opposed to
the current settings, it was suggested to add an operation attribute
that allows the client to get the factory defaults, as opposed to the
current setting, for the settable attributes. If the "factory-
defaults" (boolean) is supplied with a 'true' value, the factory
defaults are returned, instead of the current values, for any
requested settable attribute.
10. Fidelity should go away for the set operation. The set operation
should be atomic.
11. Set-Printer-Attributes operation: The "document-format" operation
attribute does have issues that were left unresolved. Issue of how
to resolve with attributes that do and don't vary with regard to
format. For example if I set n-up and media for a format of
PostScript and then Get-Printer-Attributes with a document format of
text, have I changed the values of n-up and media, or just n-up
because its value depends on the format but not media which doesn't.
The document format is a limited version of constraints.
ISSUE: Do we continue the error with Get-Printer-Attributes by
adding "document-format" to Set-Printer-Attributes or do we
acknowledge that an attribute holds all values, but some may be
constrained by constraints which are another attribute to set.
Suggested solution: Add an Interpreter object to the IPP Object
model. Those attributes that can have values depending on the
interpreter, are modeled as Interpreter object attributes, instead of
Printer attributes. Those attributes that are the same for all
interpreters, continue as Printer attributes. In the Get-Printer-
Attributes and Set-Printer-Attributes, the "document-format"
operation attribute becomes part of the target specification for
those attributes that are Interpreter attributes. Implementations
that have multiple interpreters, but don't have different values when
validating jobs, would have a single Interpreter object that
represents all interpreters.
ISSUE: Do we need a way to get and/or set the "xxx" attribute for
all Interpreter objects in one Get-Printer-Attributes or Set-Printer-
Attributes operation? Or is it sufficient for a client to provide
the equivalent functionality by stepping through all the values of
the "document-formats-supported" with repeating the Get or Set
operation?
12. Keep unsupported values rules for Set-Job-Attributes consistent to
Create-Job rules instead of new ones with new 'read-only' out-of-band
value
13. ISSUE: Make stronger what operations do with regard to other
protocols, e.g., disable should disable queue for other protocols
too. People are not unanimous on this. Some believe that admin
operation affect only the IPP channel; other believe it affect the
entire device and thus other protocols "feel" the change.
Suggested solution: While we agreed to RECOMMEND that IPP control
other protocols, we also think it would help a lot to add a Printer
Description attribute that indicates whether Printer operations
affect other protocols or not. This attribute would not be indicated
as REQUIRED to be read-only, so that some implementer's could even
allow System Administrator's to use the Set-Printer-Attributes
operation to change whether these operations do or don't affect other
protocols.
14. ISSUE: Is IPP intended for printer management. The issue is still
undetermined?
15. Shutdown-Printer operation's behavior should perhaps be left more
implementation dependent with respect to Pause/Resume of job. It is
hard for us to prescribe some printer dependent behavior as to
whether a job can be resumed after a "now" type of shutdown.
16. ISSUE 6 (Shutdown-Printer operation) and ISSUE 11 (Pause-Job
operation): The "synchronize" attribute: it is not clear why this
would ever be false. Ok to get rid of from the Shutdown-Printer and
Pause-Job operations?
17. ISSUE: It isn't clear which type of checkpointing is being
suggested for synchronize: checkpoint a stream or checkpoint in a job
that is on a disk file in the printer.
18. ISSUE 9 (Pause-Job operation), ISSUE 12 (Pause-Current-Job
operation), and ISSUE 13 (Resume-Job operation): The 'processing-
stopped' state seems like the right job state for Pause-Job and
Pause-Current-Job, rather than 'pending-held'.
19. Do we really need Pause-Current-Job. Most people felt that Pause-
Job was sufficient.
20. Promote-Job seems to have no support. No one can see a reason.
Also, it would seem that a GUI would want a drag and drop interface
that would allow a job to be move to any position in a queue. This
implies that we must define a model for how a queue is ordered and
what moving jobs does to the ordering. For example a queue might be
order by time of arrival, but the "move" operation would disrupt this
temporarily. It would not change the fact that arriving jobs would
still go to the end of the queue.
We disagreed with removing Promote-Job. We also agreed that the Get-
Jobs operation must return the promoted job(s) first, since jobs are
returned in the "expected time to complete" order. In addition we
agreed that a Printer can have more than one job in the promoted
condition at a time, even though the Promote-Job operation only
accepts one "job-id" at a time. So if an implementation does have
job queues, then the job is moved to the front of the queue.
Therefore, subsequent Promote-Job operations before the previously
promoted job started processing would just go in front of the
previously promoted job. The trick will be to specify these
semantics in such a way as to not require a queue, since that is
implementation dependent.
21. ISSUE: Does we really need a Space-Current-Job. This seems very
specific to roll-fed printers.
Suggested resolution: No. But do add a REQUIRED "job-id" operation
attribute that a client MAY supply. If supplied, then the job-id
must match the current job or the one that still has paper in the
paper path. Printers that implement Space-Printer will also have a
notion of what job is in the paper path, even though the job has
finished marking. Remember that the job is supposed to transition to
the 'completed' state when "all of the job media sheets have been
successfully stacked in the appropriate output bin(s).
22. ISSUE: Is Space-Current-Job reasonable to do in the 'processing'
state when paper is still moving?
Suggested resolution: This is now moot, since Space-Current-Job is
to be removed.
23. ISSUE: In the 'processing-stopped' state, is there a "current"
job?
Suggested resolution: This is now moot, since Space-Current-Job is
to be removed.
24. Should be Space-Job with job-id if in spec at all. Space-Current-
Job is not to be in the spec at all.
The following numbered ISSUES were not addressed in the notes, so I've
copied them here so that we have one set of issues and agreements:
25. ISSUE 2: In the Reset-Printer operation, is the "non-process-run-
out" operation attribute really needed at all or can the default
behavior for Reset-Printer be defined to be to perform non-process
run out (for continuous and cut sheet printers)?
26. ISSUE 3: In the Restart-Printer operation, is the "non-process-
run-out" operation attribute really needed at all or can the default
behavior for Restart-Printer be defined to be to perform non-process
run out (for continuous and cut sheet printers)?
27. ISSUE 4: In the Space-Printer operation, is the "non-process-run-
out" operation attribute really needed at all or can the default
behavior for Space-Printer be defined to be to perform non-process
run out (for continuous and cut sheet printers)?
28. ISSUE 5: Is the Shutdown-Printer operation, it the "non-process-
run-out" operation attribute really needed at all or can the default
behavior for Shutdown-Printer be defined to be to perform non-process
run out (for continuous and cut sheet printers)?
29. ISSUE 7: On Shutdown-Printer with "when" = 'now', is the current
job automatically restarted when the Printer is restarted? Or does
some client have to issue a Restart-Job operation?
30. ISSUE 8: On Cancel-Current-Job, why isn't non-process-run-out
automatic on a continuous form printer? When would an operator want
to cancel the job and NOT run out the last sheets.? It would be
simpler to require process-run-out when canceling the current job
(for continuous and cut sheet printers).
31. ISSUE 10: For the Pause-Job operation, is the "non-process-run-
out" operation attribute really needed at all or can the default
behavior for Pause-Job be defined to be to perform non-process run
out (for continuous and cut sheet printers)?