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Subject: Re: [wsrf] resolving issue 72: clarification of PutResourcePropertiesDocumentoperation semantics
Thus quoth Steve Graham (~ 1/7/2005 1:54 PM ~)...Hmmm. I suppose there could be a policy assertion (whatever that officially standardly means :-) ). But I'm not sure who's making it.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. 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 |
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