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Subject: RE: [ws-rx] State Tables - First June 27 version



Bob,
  still reviewing but I was thinking about the CSR event/msg and the RMS being in the None state situation, and I'm not comfortable with it transmitting an UnknownSeq Fault.  I agree that it is an incorrect thing to have happen but by saying that someone must generate an UnknownSeq Fault may be asking a bit much.  In situations like this we can not be sure which part of the soap stack will catch this bad situation - the state table is assuming that RM will be the one.  However, it may not be because there are actually two bad things going on here - one for RM and one for WSA.  Its possible that the WS-Addressing layer could look at the message, notice the wsa:RelatesTo, try to find a waiting request message to match it up, and finding none just ignores the message - or generates some other kind of fault.  I'd prefer if we put something else in that box, like N/A.  Not a show-stopper, just don't like the implication on soap stacks that the current entry implies.
  The other part of this that worries me is that the state table says "Xmit" the fault - and if the CSR came back on a back-channel then it can't do that.  This may go back to the issue of Xmit vs Generate for all Xmits in the table.
  I think this concern would apply to the other events/msgs that are related to Respone messages.

thanks,
-Doug



"Bob Freund-Hitachi" <bob.freund@hitachisoftware.com>

06/28/2006 06:50 PM

To
Doug Davis/Raleigh/IBM@IBMUS, <ws-rx@lists.oasis-open.org>
cc
Subject
RE: [ws-rx] State Tables - First June 27 version





Doug.
 
It was very hard for me to make the state table reflect the text that I found and not what I thought the protocol should do.
 
I made a distinction between blank which I thought to be unspecified or invalid behavior, and N/A which is internal behavior inconsistent in the given state. The state table is not a general state table for a machine capable of processing wsrm messages, but rather it is a state table that describes behavior with respect to the lifetime of a sequence.  N/A in general represents combinations that I thought to be impossible or self inconsistent.  An example of this is the Create Sequence event from an unspecified motivator that starts the ball rolling.  Perhaps in incorrect implementation of an RMS might have this event occur to a sequence that already exists, but it is not an event that has any external appearance on the wire and thus has meaning to the RMS state table only while in the None state.  
To illustrate this distinction take the case of receipt of a CSR while in the None state.  In the None state, there is no knowledge of the sequence, it does not yet exist, thus I chose to apply the unknown sequence fault due to its description in Section 4.3, unless message in its context has some sort of special meaning.  In the closed state, the sequence is known, but there is no text I can find that expresses what should be done.  Perhaps, since this might be an unrecoverable state or protocol error, a Sequence Terminated fault as described in Sec 4.2 might be appropriate, but the definition of protocol error exists in only its plain reading but does not otherwise what messages received at what time constitute such an error.
 
The CreateSequenceRefused fault’s reception while in the none state was a close call.  Note that I specified that the fault is dropped with a reference of unspecified which roughly means that I made it up (my bad).  Strictly speaking, I am not sure that the CSRefused fault contains a sequence identifier or not since its detail element is only defined as xs:any, so I could not make up my mind if it was targeted to a sequence or not (*maybe there is a new issue here*).
If it is not sequence targeted, then in the none state it could by N/A, but since it is a potential message from the other side of the wire it could be a sequence Terminated fault.  My error was not leaving this cell as blank since I don’t this the spec says what should happen here.
 
One problem for me as I worked to construct these tables is that we are not very good at making the distinction of generating a fault and transmitting a fault message.  Many of these ought to be transmitted as fault messages since efficient state recovery depends to some degree on these fault messages to be used as signals from one side of the wire to the other.  I opened an issue for more precise statements of source and action for each fault partially due to this lack of clarity.  Perhaps there ought to be a flavor or two of faults that might be generated but not transmitted for local purposes that can be used for such circumstances.
 
-For Send message in the rollover state the spec does not specify when message rollover occurs precisely. That is why there a Reached max msg number internally sourced event.  I imagined that if the RMS was in rollover state for whatever reason, the sequence was going to have to wind down.  We know that the transfer of some prior message was faulted by the RMD or that the RMS itself determined that the message about to be sent generated a MessageNumber too high.  Anyway, I did not include a section reference here since there is none describing this situation.  We also do not have a fault that is used to convey such a situation.  Perhaps I should have left this cell blank too and not attempted to make an unreferenced guess about correct operation.  The fix for this cell is to make some text somewhere state what it should do or to point me to where I missed it which is a distinct possibility.
 
-Close Sequence event.  The motivator for close sequence is not specified; indeed it is an optional concept as indicated by its MAY language from whence I derived its definition.  I think that you caught an error of mine. The cells should be N/A in Closed and Terminated.  I agree that is something that I should fix.  I have some difficulty with this event in the connecting state, since it is conceivable that the RMS might to close the sequence at any time and indeed that includes the connecting state where the RMS has not yet created the sequence (since it is not created until the CSR is successfully processed and the Sequence ID in known.  I think that No Action [None] might be applied here although it might leave an orphaned sequence for the RMD to clean up some day.  As for CloseSequence re-transmissions, there is nothing that describes re-transmissions in any specific way.  I don’t think it should be the re-triggering of the close sequence event.  I suspect that especially dur to the new polling stuff that I might enjoy construction a “MEP” engine that might operate underneath the Sequence State machine to handle re-transmission and polling.  Re-transmission behavior probably should be moved entirely to that new state table when we decide it is warranted.
 
-Terminate Sequence[int] none state:  You there is a problem with this row  Should be N/A | No Action[none] | STET | STET | STET | N/A
In the connecting state although the RMS may have sent a sequenceID, the RMS has not yet processed it.  It is a valid condition, but the correct next state is None with no action since there is no sequence yet to terminate.  Spec text might be tightened here.  Can you suggest where? * Perhaps some words that define Sequence Lifetime ought to be included in Sec 3.4*.
 
-TernSeqRed event well in the None and Connecting State I guess it ought to be the unknown seq fault  I will fix  In the other states other than Terminating I left it blank since the behavior is unspecified as far as I can determine.  Perhaps this is a good use of SequenceTerminated fault transmission to the RMS.
 
-Expires: you are correct, but the spec doesn’t say.  I opened an issue on this one
 
The last row is an event raised by the receipt of an invalid acknowledgment range (see section 4.4)  Its tribber is the receipt of any ack range that is invalid
 
RMD
-CloseSeq message, I disagree, according to sec 4.7, the attempt to close a sequence that is already closed results in this fault.
-Expires: Yup, where does the spec say what it should do? (issue proposed on this one)
-Non-RM message: you are correct, I will fix
 
Thanks for reviewing
-bob
 
 
 



From: Doug Davis [mailto:dug@us.ibm.com]
Sent:
Wednesday, June 28, 2006 12:23 PM
To:
ws-rx@lists.oasis-open.org
Subject:
Re: [ws-rx] State Tables - First June 27 version

 

Bob,

comments about the state tables:


RMS:

- not sure I see the diff between "blank" and "N/A".  In both cases its abnormal behavior.  Take for example the receipt of a CSR w/o sending a CS - why would being the "none" state be any different from being in a "closed" state.  Both would require the rejection of the message and no change in the state.

- On CreateSeqRefused fault - I would think the action wouldn't be "none" - something more like generate fault since something needs to tell the AS (or the admin) that the sequence was refused. But this gets a bit close to leaving our scope.

- For the "Send message" event, in the "Rollover" state, I wouldn't have said "No action" in that case I would have said "generate fault" or something - since I believe you're assuming that the msg numbers got too high, right?

- I think the same is true for the max msg num reached event too - seem like some fault should be generated instead of "no action"

- CloseSeq event - Closing state - I think it should resend the Close message instead of "n/a" since it may need to resend it.

- CloseSeq event - Closed or Terminating states - I think those should be blank or N/A since that should never happen

- Terminate Seq [int] event - None state - I think that should be blank since it shouldn't ever happen

- Terminate Seq [int] event - Connecting state - I don't think you want to generate a fault since its an internal event - instead we should just move to the terminating state

- TermSeqRes event - I would think that all states (except terminating) would either generate some fault or be blank (since it should never happen) - don't understand why "none" state is different or why it doesn't generate an UnknownSeq fault.

- Expires - shouldn't this cause some action for some states?  Like terminate the seq?

- InvalidAck [msg] event - I think this highlights some of the inconsistencies I think are in the table - in the first two states we generate an unkownSeqFault but in other spots in the table we have either "no action" or blank for similar "never should happen" cases. We need to be consistent.

- Actually, what is the last row/event?  is that meant to be InvalidAck Fault?  We don't have an invalid Ack msg just a fault.  If its supposed to be a fault msg then I don't see why we would generate an invalid ack fault by receiving this msg.


RMD:

- CloseSeq msg, Closed state -> should be no action, not xmit SeqClosed fault

- Expires - shouldn't this cause some action for some states?  Like terminate the seq?

- Non-RM msg event - should be "WSRM Required Fault" instead of just "WSRM Fault"


thanks,

-Doug


"Bob Freund-Hitachi" <bob.freund@hitachisoftware.com>

06/27/2006 09:52 AM


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"[WS-RX]" <ws-rx@lists.oasis-open.org>
cc
 
Subject
[ws-rx] State Tables - First June 27 version

 


   





Added references, removed gratuitously applied protocol fault responses to change them to unspecified.

Corrected a few cells[attachment "wsrm-1.1-spec-wd-15-ith-ST-Edits.doc" deleted by Doug Davis/Raleigh/IBM]



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