Re: [wsrf] resolving issue 72: clarification of PutResourcePropertiesDocumentoperation semantics

[Fred Carter <fred.carter@amberpoint.com>]

Thus quoth Steve Graham (~ 1/7/2005 1:54 PM ~)...

Hi Fred:
What I was pushing at was something like this , if we do have this (which 
I am not very keen on) that has this level of implementation variability, 
then there needs to be some sort of policy assertion to clarify for the 
requestor what to expect before it sends the PutRPDoc message.
  

Hmmm.  I suppose there could be a policy assertion (whatever that officially standardly means :-) ).  But I'm not sure who's making it.

If it's an attribute on the request, then I think that the requestor is stating the policy "[this is my desired state but] I'll take what I can get".  I'm not sure what the callee would want to say about it.  Such an option might be an optional capability, I suppose, in which case said service might wish to utter a statement defining the capabilities it supported.  But some policy here and on the client about this would seem pointless.  Unless the goal is employ a bunch of other computers as legal advisors for the web yammering endlessly about resource services (LAWYERS -- sorry, couldn't resist).

sgg

++++++++
Steve Graham
(919)254-0615 (T/L 444)
STSM, IBM Software Group, Web services and SOA
Member, IBM Academy of Technology
<Soli Deo Gloria/>
++++++++




Fred Carter <fred.carter@amberpoint.com> 
01/07/2005 04:34 PM
Please respond to
fred.carter


To
"Sedukhin, Igor S" <Igor.Sedukhin@ca.com>
cc
Steve Graham/Raleigh/IBM@IBMUS, wsrf@lists.oasis-open.org
Subject
Re: [wsrf] resolving issue 72: clarification of 
PutResourcePropertiesDocument operation semantics






In general, if this is all a big deal, why not deal with it like pretty 
much all other computer instructions do:  have an option.

In Windows/Macintosh/whatever, if I copy a folder/directory over top of 
another, pop-op boxes may appear which say words to the effect "you've 
already got a file named foo, do ya wanna stop, overwrite this one, or 
overwrite them all."  Or if there are files that are readonly, not owned 
by me, munged beyond words, etc.  Similarly, at CLI land, if I remove 
things, I get "override permission XXX?" type questions left & right.

Why not just offer an option of front?  Default is to fault if somethings 
are not writeable by the sender (or by anyone), but allow an option to 
"silently ignore" such situations.  changeWhatYouCan=true or whatever. :-) 
 It might return some status "some junk changed", depending upon how 
silent one wished to be...

Suggestion offered.  No strong opinion one way or the other.  But it seems 
like a reasonable compromise...  Not without precedence in system 
services, certainly not in UI's.

/fred

Thus quoth Sedukhin, Igor S (~ 1/7/2005 1:17 PM ~)...
It is always implementation specific. The client needs to understand (or
guess :) the semantics of the implementation anyways. There is no such
absolute knownledge that a temperature property is not settable and has
this or the other effect. It is always relative to the client's
understanding of what the implementation will actually do. However, what
we provide is a MEP which takes care of some of the basic aspects of
this interation and makes that, at least, interoeprable. I think we're
fine.
 

-- Igor Sedukhin .. (igor.sedukhin@ca.com)
-- (631) 342-4325 .. 1 CA Plaza, Islandia, NY 11749 

 

  _____ 

From: Steve Graham [mailto:sggraham@us.ibm.com] 
Sent: Friday, January 07, 2005 4:12 PM
To: Sedukhin, Igor S
Cc: wsrf@lists.oasis-open.org
Subject: RE: [wsrf] resolving issue 72: clarification of
PutResourcePropertiesDocument operation semantics



yes, good example. 
However, the semantics of SetRP on temperature are clear, client expects
the fault.  From what I understood of your proposal, it is implemntation
specific what exactly happens to the temperature. 

++++++++
Steve Graham
(919)254-0615 (T/L 444)
STSM, IBM Software Group, Web services and SOA
Member, IBM Academy of Technology
<Soli Deo Gloria/>
++++++++




"Sedukhin, Igor S" <Igor.Sedukhin@ca.com> 

01/07/2005 03:50 PM 

To
Steve Graham/Raleigh/IBM@IBMUS 
cc
<wsrf@lists.oasis-open.org> 
Subject
RE: [wsrf] resolving issue 72: clarification of
PutResourcePropertiesDocument operation semantics

 




Steve, like I said, the same concern is true of any property update. 
 
Say I have 
 
<myCrazyThermometer> 
<temperature>...</temperature> 
<message>...</messaage> * 
</myCrazyThermometer> 
 
The client does SetRP(<temperature>X</temperature>). My impl sends a
fault, but also records a message that someone tried to update the
temperature. So that is the side effect. 
 
Now I got the RP doc which may be very surpising to the client. The
client may not have intended this effect of the SetRP operation, but
will have to live with it anyways. 
 
<myCrazyThermometer> 
<temperature>Y</temperature> 
</message>Client A tried to update! Bad client! Kill him!</message> 
</myCrazyTehrmometer> 

-- Igor Sedukhin .. (igor.sedukhin@ca.com <mailto:igor.sedukhin@ca.com>
)
-- (631) 342-4325 .. 1 CA Plaza, Islandia, NY 11749 




  _____ 

From: Steve Graham [mailto:sggraham@us.ibm.com] 
Sent: Friday, January 07, 2005 3:39 PM
To: Sedukhin, Igor S
Cc: wsrf@lists.oasis-open.org
Subject: RE: [wsrf] resolving issue 72: clarification of
PutResourcePropertiesDocument operation semantics


"Sedukhin, Igor S" <Igor.Sedukhin@ca.com> wrote on 01/07/2005 03:27:38
PM:

 
Steve, 
 
I don't think it is as scary as you describe. First of all any MEP
 
that changes 
 
values may result in unitended behaviour in that when the fault occurs
 
e.g. an 
 
exception in the implementation code, there is no "undo" and the state
 
of the 
 
resource properties document MAY be undetermined. 
 
True, but at least the behavior of the web service, independent of
implementation 
issues is known a priori.  If I try to do a SetResourceProperties MEP on
an RP that 
is read only, I know it will fault, this is part of the definition.
However, from 
what I read, if I do a PutRPDoc including some Read-only properties, the
provider may 
make certain changes but not all, it may update everything, including
read-only properties 
(as a surprise to all concerned) or it may update some properties, not
others, etc. etc. 
My point is that with a MEP that does change state like this, we cannot
be so flexible 
with the semantics. 

 
That aside, I believe that 
particular rule of this MEP is interoperable: 
    A. it says that Put MUST contain an XML Schema valid RP doc, so
 
the client 
 
knows what to do 
    B. unless a fault was returned, the client unambiguously knows
 
what happened at
 
the WS-Resource end: the new document is either exactly the same as
 
the one 
 
submitted or different in which case the new one is returned. 
 
But the client may still be surprised that certain values did change
when the client 
expected them to stay the same. 

 
 
I guess you refer to the case when a client intends to update
 
something, but it 
 
does not get updated or something else that was not intended is
 
updated (side 
 
effects). However, that is true of any form of update. 
 
-- Igor Sedukhin .. (igor.sedukhin@ca.com)
-- (631) 342-4325 .. 1 CA Plaza, Islandia, NY 11749 
 

From: Steve Graham [mailto:sggraham@us.ibm.com] 
Sent: Friday, January 07, 2005 8:32 AM
To: Sedukhin, Igor S
Cc: wsrf@lists.oasis-open.org
Subject: Re: [wsrf] resolving issue 72: clarification of 
PutResourcePropertiesDocument operation semantics
 

 
Hi Igor: 
Thanks for clarifying your position on PutRP doc. 
My concerns remain about the vagueness of the semantics of this, and
 
hence my 
 
continued concern about adding this MEP.  In particular, 
 
rule 1.B: the WS-Resource implementation is free to interpret the
 
resource 
 
properties document contained in the Put request in any way it deems
 
necessary for 
 
the update to occur. 
 
The freedom for an implementation to interpret the request in which
 
ever way it 
 
seems best strikes me as a HUGE interoperability threat.  How is a
 
requestor to 
 
figure out what the actual interpretation might be?  Further, given
 
this is a MEP 
 
that potentially changes values in the WS-Resource, we must treat this
 
MEP 
 
carefully, it might be difficult or impossible for the requestor to
 
"undo" the 
 
results, if it later deems that the implementation interpreted the
 
request in a 
 
"surprising" way. 

sgg
++++++++
Steve Graham
(919)254-0615 (T/L 444)
STSM, IBM Software Group, Web services and SOA
Member, IBM Academy of Technology
<Soli Deo Gloria/>
++++++++


 

 
"Sedukhin, Igor S" <Igor.Sedukhin@ca.com> 
01/06/2005 11:57 PM 

To 

<wsrf@lists.oasis-open.org> 

cc 

Subject 

[wsrf] resolving issue 72: clarification of
 
PutResourcePropertiesDocument operationsemantics 
 



Responding to my AI [(Igor) Put forward a proposal to resolve issue 72
 
- how this 
 
would be done with respect to the semantics issues etc.] 
 
I suggest to define the following semantics for the
 
PutResourcePropertiesDocument 
 
operation. The words are precise, so may not be easy to read. Let me
 
know if this 
 
needs further clarifications or not. 
rule 1: a resource properties document SHOULD be contained in the Put
 
request, in 
 
which case the WS-Resource implementation MUST interpret the request
 
as an update 
 
of the resource properties document. 
rule 1.A: the resource properties document contained in the Put
 
request MUST be XML
 
Schema valid. 
rule 1.B: the WS-Resource implementation is free to interpret the
 
resource 
 
properties document contained in the Put request in any way it deems
 
necessary for 
 
the update to occur. 
rule 1.B.I: if the resource properties document maintaned by the
 
WS-Resource after 
 
update is XML Infoset identical to the resource properties document
 
contained in 
 
the Put request, then response MUST contain nothing. 
rule 1.B.II: if the resource properties document maintaned by the
 
WS-Resource after
 
update is not XML Infoset identical to the resource properties
 
document contained 
 
in the Put request, then response MUST contain the updated resource
 
properties document. 
 
rule 3: in principle any document MAY be contained in the Put request,
 
in which 
 
case the WS-Resource implementation MAY find sufficient information in
 
the request 
 
to interpret it as an update of the resource properties document. The
 
response then
 
MUST contain the updated resource properties document. This behaviour
 
is 
 
implementation specific. 
Note that rule 3 is covering the case where the resource properties
 
document 
 
submitted in Put request in not XML Schema valid (e.g. a partial
 
document with some
 
required properties omitted). The rule 1.B.I is covering the case
 
where the 
 
document is valid, but may fill the values that are assigned by the
 
WS-Resource 
 
implementation e.g. IDs, static values, default values, calculated
 
values, 
 
transient values, etc. Either way it is up to the implementation to
 
interpret Put, 
 
however, I believe, it is sufficiently interoperable if the client can
 
count on 
 
these rules to be in effect. 
-- Igor Sedukhin .. (igor.sedukhin@ca.com)
-- (631) 342-4325 .. 1 CA Plaza, Islandia, NY 11749 
 


 


  

-- 
Fred Carter / AmberPoint, Inc.

mailto:fred.carter@amberpoint.com
tel:+1.510.433.6525 fax:+1.510.663.6301