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Subject: RE: [sca-assembly] ISSUE 6 - alternate proposal - Version 2 !
Hi Dave, How do we proceed from now on ? Do you prefer to try to address those points in the current proposal or postpone them as other issues ? Best Regards Peter -----Original Message----- From: David Booz [mailto:booz@us.ibm.com] Sent: Thursday, 15. November 2007 19:03 To: sca-assembly@lists.oasis-open.org Subject: RE: [sca-assembly] ISSUE 6 - alternate proposal - Version 2 ! Hi Peter, Ok, good. It should also be possible for tools to detect such a SCDL validation problem long before it gets to deployment. I'd say this is similar to a compile error. Also don't forget about the @wiredByImpl would would put another twist on when a reference is validly targetted. On your second point, I see the distinction now. I keep forgetting that wires can be deployed which change an already deployed composite. I really wish that wasn't possible, so I mentally block out that case. :-( Dave Booz STSM, SCA and WebSphere Architecture Co-Chair OASIS SCA-Policy TC "Distributed objects first, then world hunger" Poughkeepsie, NY (845)-435-6093 or 8-295-6093 e-mail:booz@us.ibm.com http://washome.austin.ibm.com/xwiki/bin/view/SCA2Team/WebHome "Peshev, Peter" <peter.peshev@sap .com> To David Booz/Poughkeepsie/IBM@IBMUS, 11/15/2007 01:51 <sca-assembly@lists.oasis-open.org> AM cc Subject RE: [sca-assembly] ISSUE 6 - alternate proposal - Version 2 ! Hi Dave, Answering in reverse order : So you are suggesting the case of multiplicity 1..1 / 1..n and having no target in case the wiring is NOT on the domain (i.e. no way to be changed by another contribution) to be treated as SCDL validation error in another section, and probably lead to error during deployment. That makes a lot of sense to me. Yes, there is distinction between -- the target service has not yet been deployed -- a reference indicates no target service, bit another contribution can potentially deploy a wire that has source this reference. I thought we could describe them together, since there are some similarities (In both of the cases we can say that such a deployment is valid, however until the reference is resolved the component cannot be used. - "an error MUST be generated by the SCA runtime before the reference is invoked by the component implementation." .) However splitting the two cases in two different sections as you suggested can be better. Best Regards Peter -----Original Message----- From: David Booz [mailto:booz@us.ibm.com] Sent: Wednesday, 14. November 2007 21:49 To: sca-assembly@lists.oasis-open.org Subject: RE: [sca-assembly] ISSUE 6 - alternate proposal - Version 2 ! Hi Peter, I'll use your numbering to respond. A) There is a difference between a reference which indicates a target service(s) which has not yet been deployed vs a reference which indicates no target service(s). The latter is described by the text that you pointed out in 1). The former is an independent discussion that has to do with when and how a specified target is resolved from the perspective of a reference. We should not confuse these two cases. Autowire introduces a twist because it enables the latter to potentially behave like the former in that deployment of a composite _might_ produce a reference target. I think we would need another section to describe the behavior of the former case +/- autowire. B) I would put this in the category of SCDL validation errors. We probably need some text in section 6.5 [1] or a new section. 2) Agree, but what's the difference between this case and (B)? [1] sca-assembly-draft-20070924.pdf Dave Booz STSM, SCA and WebSphere Architecture Co-Chair OASIS SCA-Policy TC "Distributed objects first, then world hunger" Poughkeepsie, NY (845)-435-6093 or 8-295-6093 e-mail:booz@us.ibm.com http://washome.austin.ibm.com/xwiki/bin/view/SCA2Team/WebHome "Peshev, Peter" <peter.peshev@sap .com> To David Booz/Poughkeepsie/IBM@IBMUS, 11/14/2007 11:27 <sca-assembly@lists.oasis-open.org> AM cc Subject RE: [sca-assembly] ISSUE 6 - alternate proposal - Version 2 ! Hi, I also think that it's better to finish this one. However just wanted to mention two points, which perhaps can be addressed as separate issues later. 1) The sentences in the proposal are : For references with multiplicity 1..1 or 1..n, it is an error for the reference to have no target service defined. .... For the error cases identified above, an error MUST be generated by the SCA runtime before the reference is invoked by the component implementation. As discussed earlier in the mailing thread and posted by Mike E. and Anish we may wish to distinguish two possible sub-cases A) The case when the problem could be fixed by another contribution (i.e. the target will be on a domain level). In that subcase we may defer the exception to the first usage of the component. (Michael R. has suggested as well thinking about batch deployment) B) The case when a missing reference target simply cannot be fixed by another contribution. (i.e. non-promoted reference / use of Composite as a component implementation). In that subcase it's safe to say there is MUST for exception during deploy time 2) The proposal is very detailed and descriptive (much better than I would have hoped to do it myself). It is speaking about - lack of target \ having target via (@target attribute, etc.). Just to make the spec bulletproof, we may also cover the somewhat obvious case what should happen if there is specified target but it is wrong ( (invalid component\service name in the @target attribute, there is @autowire but no suitable implementation, etc.) Maybe we can have wording "in case the target can not be identified, then the deploy\runtime behavior will be the same as if there is no target specified." Another possibility would be to craft the term "valid target". Best Regards Peter -----Original Message----- From: David Booz [mailto:booz@us.ibm.com] Sent: Tuesday, 13. November 2007 18:11 To: sca-assembly@lists.oasis-open.org Subject: Re: [sca-assembly] ISSUE 6 - alternate proposal - Version 2 ! It looks good to me. As far as I can tell, it has the same technical points that I wanted to cover, with the additional dimension of autowire included. I think that's good. Your proposal is more verbose, but sometimes that can be beneficial. I spotted one typo in the following; delete one of "created" or "implied". I prefer created. Where the reference has a value specified in its @target attribute, all the binding types identified by the child binding elements are available for use on each wire created implied by the @target attribute. Final comment in passing. We need to take a look at the Wires section (6.4 currently) and align it with this new text also. But that's going to be alot more work that might be better done under a seperate issue. This one is starting to get large and we aren't really changing anything, just clarifying. Dave Booz STSM, SCA and WebSphere Architecture Co-Chair OASIS SCA-Policy TC "Distributed objects first, then world hunger" Poughkeepsie, NY (845)-435-6093 or 8-295-6093 e-mail:booz@us.ibm.com http://washome.austin.ibm.com/xwiki/bin/view/SCA2Team/WebHome Mike Edwards <mike_edwards@uk. ibm.com> To "OASIS Assembly" 11/13/2007 09:27 <sca-assembly@lists.oasis-open.org> AM cc Subject Re: [sca-assembly] ISSUE 6 - alternate proposal - Version 2 ! Dave, I've been pondering this some more and I think there is a need to go further than your proposal text. The main issue here is to define what it means for a reference to have one or more target services configured, either through wiring or through promotion: a) Wiring through promotion by a composite reference element b) Wiring through the use of value of @target on the enclosing reference element c) Identification of a target service through the @uri attribute on the binding element d) Identification of a target service through binding-specific attributes and child elements, as defined in the specification for the specific binding e) autowire ....and that is the order of precedence.... In order to deal with all this, I think that we must introduce a new subsection into the specification, to follow line 330: 3.0.1 Specifying the Target Service(s) for a Reference A reference may define one or more target services which satisfy the reference. The target service(s) may be defined in the following ways: 1) Through a value specified in the @target attribute of the reference element. 2) Through a target URI specified in the @uri attribute of a binding element which is a child of the reference element 3) Through the setting of one or more values for binding-specific attributes and/or child elements of a binding element which is a child of the reference element 4) Through the specification of @autowire="true" for the reference (or through inheritance of that value from the component or composite containing the reference) 5) Through the promotion of a component reference by a composite reference of the composite containing the component (the target service is then identified by the configuration of the composite reference). Some combinations of these different methods are not allowed: If @autowire="true" applies to the reference, the autowire procedure is only used to find a target service if no target is identified by any of the other ways listed above. It is not an error if autowire="true" applies to a reference and a target is also defined through some other means. If a reference has a value specified for one or more target services in its @target attribute, the child binding elements, of that reference MUST NOT identify target services using the @uri attribute or using binding specific attributes or elements. If a binding element has a value specified for a target service using its @uri attribute, the binding element MUST NOT identify target services using binding specific attributes or elements. It is possible that a particular binding type MAY require that the address of a target service uses more than a simple URI. In such cases, the @uri attribute MUST NOT be used to identify the target service - instead, binding specific attributes and/or child elements must be used. Where the reference has a value specified in its @target attribute, all the binding types identified by the child binding elements are available for use on each wire created implied by the @target attribute. 3.0.1.1 Multiplicity and the Valid Number of Target Services for a Reference For references with multiplicity 0..1 or 0..n, it is valid for the reference to have no target service defined. For references with multiplicity 0..1 or 1..1, it is an error for the reference to have more than 1 target service defined. For references with multiplicity 1..1 or 1..n, it is an error for the reference to have no target service defined. For references with multiplicity 0..n or 1..n, it is valid for the reference to have 1 or more target services defined. The assembler of a composite MUST ensure that references are properly configured according to these rules. For the error cases identified above, an error MUST be generated by the SCA runtime before the reference is invoked by the component implementation. For the cases where it is valid for the reference to have no target service specified, the component implementation language specification defines the programming model for interacting with an untargetted reference. Where a component reference is promoted by a composite reference, the promotion is treated from a multiplicity perspective as providing 0 or more target services for the component reference, depending upon the further configuration of the composite reference. These target services are in addition to any target services identified on the component reference itself, subject to the rules relating to multiplicity described in this section ---------------------------------------------------------------------- Replace lines 274 - 280 with the following: "A reference may identify one or more target services which satisfy the reference. This can be done in a number of ways, which are fully described in section "3.0.1 Specifying the Target Service(s) for a Reference". Replace lines 1424 - 1430 with the following: "A reference may identify one or more target services which satisfy the reference. This can be done in a number of ways, which are fully described in section "3.0.1 Specifying the Target Service(s) for a Reference". Replace lines 2372 - 2383 with the following: uri - has the following semantic The uri attribute can be omitted. For the binding of a reference, the uri attribute defines the target URI of the reference. This can be either the componentName/serviceName for a wire to an endpoint within the SCA domain, or the accessible address of some service endpoint either inside or outside the SCA domain (where the addressing scheme is defined by the type of the binding). The circumstances under which the uri attribute can be used are defined in section 3.0.1 Specifying the Target Service(s) for a Reference Yours, Mike. Strategist - Emerging Technologies, SCA & SDO. Co Chair OASIS SCA Assembly TC. IBM Hursley Park, Mail Point 146, Winchester, SO21 2JN, Great Britain. Phone & FAX: +44-1962-818014 Mobile: +44-7802-467431 Email: mike_edwards@uk.ibm.com Unless stated otherwise above: IBM United Kingdom Limited - Registered in England and Wales with number 741598. Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU --------------------------------------------------------------------- To unsubscribe from this mail list, you must leave the OASIS TC that generates this mail. You may a link to this group and all your TCs in OASIS at: https://www.oasis-open.org/apps/org/workgroup/portal/my_workgroups.php ----- Message from "Mike Edwards" <mike_edwards@uk.ibm.com> on Tue, 30 Oct 2007 16:01:17 +0100 ----- To: "OASIS Assembly" <sca-assembly@lists.oasis-open.org> Subject: RE: [sca-assembly] ISSUE 6: usage of not promoted references Folks, I think that there is still a problem here that has not been tackled. I think that it is all down to the usage intended for the composite. I believe that there are 2 cases and that they are distinct: a) Use of a composite as a component implementation. b) Use of a composite for inclusion into the Domain (ie where the composite's contents become part of the Domain). I leave out the case of a composite being included into another composite - the rules for that case are actually then simply applied to the containing composite.... Case A. Use of Composite as a component implementation In this case, there is nothing that will ever occur that can change or add to the wiring within the composite. If it is not complete at the time the composite is used as an implementation, then it never will be complete and there is an error. The error can be generated as soon as the using component is deployed. Case B. Use of a composite for inclusion into the Domain. This is VERY different for the simple reason that either some wire targets may get added to the Domain later than the composite, or that the wires themselves may be added to the Domain later than the composite. There can be no error up until the moment that someone tries to invoke the service(s) provided by a component whose references are not wired - and only then for cases where the multiplicity is 1..1 or 1..n. We may have to look much harder at some of the dynamic aspects of Case B before we can give proper words to the spec. Yours, Mike. Strategist - Emerging Technologies, SCA & SDO. Co Chair OASIS SCA Assembly TC. IBM Hursley Park, Mail Point 146, Winchester, SO21 2JN, Great Britain. Phone & FAX: +44-1962-818014 Mobile: +44-7802-467431 Email: mike_edwards@uk.ibm.com "Peshev, Peter" <peter.peshev@sap.com> 29/10/2007 07:57 To "David Booz" <booz@us.ibm.com>, <sca-assembly@lists.oasis-open.org> cc "Blohm, Henning" <henning.blohm@sap.com>, "Martin Chapman" <martin.chapman@oracle.com>, "Michael Rowley" <mrowley@bea.com> Subject RE: [sca-assembly] ISSUE 6: usage of not promoted references Just to make a summary - it seems the text & the proposal are accepted, and the only exception is what should happen in case there is reference with multiplicity 1..1 or 1..n , however it is not wired. Initially that was proposed as deployment error, however since both Dave & MR seems to prefer a runtime error during the first usage to the component, the proposal is updated to reflect their opinion. Btw, I would assume the same behavior should happen in case the target of the reference is component, which is invalid. Since the same arguments can apply (the target component may come as later contribution), then there should be NO deployment error and the same runtime error during the first usage should happen. @Dave & Michael -- what's your opinion on this & do you think that we should add a text about that case in the proposal or that is another issue ? PROPOSAL The following description should be added in section 1.6.2 References, after line 1387 (that line is after the paragraph that explains attaching a binding to a reference and before the paragraph explaining callback) : Promotion of references accessing endpoints via bindings is suggested practice since it allows the assembler to change the targets of the references or the specified bindings and encourages component reuse, however the lack of such promotion by itself MUST NOT cause errors during deployment or runtime if the target of the reference can be identified. The assembler is expected to guarantee for an unpromoted reference with multiplicity 1..1 or 1..n that one of the following conditions holds : there is either internal wire within the scope of the current composite or a binding that identifies correctly either the component/service for a wire to an endpoint within the SCA domain or the accessible address of some endpoint outside the SCA domain. If the assembler does not provide these conditions for a reference that has a multiplicity of 1..1 or 1..n, then such an unresolved reference MUST generate a runtime error at latest during the first attempt to use the component. If the assembler does not provide these conditions for a reference that has a multiplicity with 0..1 or 0..n , then the programming model MUST not generate deployment errors and the reference's wiring state will be represented in accordance to the implementation type in question (e.g. null, handle that throws exceptions when accessed, extensibility hooks, etc.). For example the following definitions MUST NOT generate deployment error : <composite xmlns="http://www.osoa.org/xmlns/sca/1.0" name="MyValueComposite"> <component name="MyValueServiceComponent"> <implementation.java class="services.myvalue.MyValueServiceImpl"/> <reference name="StockQuoteService"> <binding.ws uri=",http://www.sqs.com/StockQuoteService"/> </reference> <reference name="StockQuoteService2"> <binding.jms> <destination name="StockQuoteServiceQueue"/> <connectionFactory name="StockQuoteServiceQCF"/> </binding.jms> </reference> </component> <!-- no references and promotion on purpose --> <composite> however the following definitions MUST generate one : <composite xmlns="http://www.osoa.org/xmlns/sca/1.0" name="MyValueComposite"> <component name="MyValueServiceComponent"> <implementation.java class="services.myvalue.MyValueServiceImpl"/> <reference name="UnwiredReference"> <!-- the target cannot be determined, thatshouldbean error--> <binding.ws/> </reference> </component> <!-- no references and promotion on purpose --> <composite> -----Original Message----- From: David Booz [mailto:booz@us.ibm.com] Sent: Saturday, 27. October 2007 00:18 To: sca-assembly@lists.oasis-open.org Cc: Blohm, Henning; Martin Chapman; Michael Rowley Subject: RE: [sca-assembly] ISSUE 6: usage of not promoted references I agree with Mike R's comments. I don't think we should complicate multiplicity. In my mind, your second and third cases are not distinct because they occur at different points in the lifecycle of the composite. I think we should assert that it is just not possible to detect an error in these cases until the component owning the reference is started/initialized/dispatched (whatever word you want to use, they are all the same to me). That is, I don't think we should attempt to support your 3rd point. A batch deployment mechanism with special validation semantics sounds like an interesting vendor extension. Since this kind of extended behavior effectively constrains what can be successfully deployed, it doesn't make the app incompatible with a vendor that doesn't do batch deploy + validation. Dave Booz STSM, SCA and WebSphere Architecture Co-Chair OASIS SCA-Policy TC "Distributed objects first, then world hunger" Poughkeepsie, NY (845)-435-6093 or 8-295-6093 e-mail:booz@us.ibm.com http://washome.austin.ibm.com/xwiki/bin/view/SCA2Team/WebHome "Peshev, Peter" <peter.peshev@sap .com> To "Michael Rowley" <mrowley@bea.com>, 10/24/2007 02:00 "Martin Chapman" PM? <martin.chapman@oracle.com>, "Blohm, Henning" <henning.blohm@sap.com>, "OASIS Assembly" <sca-assembly@lists.oasis-open.org> cc Subject RE: [sca-assembly] ISSUE 6: usage of not promoted references Hi Michael, Thanks very much for the clarification, now I understood what you had in mind.>, Do you think that would lead to a new option for multiplicity (maybe raised as another issue ) ? Since it seems we are wanting to cover 3 scenarios in case the target is unavailable -- error during first use of the reference (the 0..1) -- error during first instantiation of component (what you are suggesting for 1..1 in order to solve the bulk deployment for cross-referenced components) -- error during deployment (1..1 in the current proposal, and what probably many people would expect. I.e. even if such spec expert as you thought for a moment this is the 1..1 meaning, than obviously the mortal guys (me & the assemblers) may be thinking the same meaning as well :) Best Regards Peter From: Michael Rowley [mailto:mrowley@bea.com] Sent: Wednesday, 24. October 2007 20:32 To: Peshev, Peter; Martin Chapman; Blohm, Henning; OASIS Assembly Subject: RE: [sca-assembly] ISSUE 6: usage of not promoted references From: Peshev, Peter [mailto:peter.peshev@sap.com] Sent: Wednesday, October 24, 2007 12:40 PM To: Martin Chapman; Blohm, Henning; Michael Rowley; OASIS Assembly Subject: RE: [sca-assembly] ISSUE 6: usage of not promoted references HI Michael, Since the old text got too much inlined and I am usually confused with that, I will try to summarize the opened sub-issues. - you are saying "Having 1..1 instead of 0..1 could mean that an error should be generated at runtime, possibly at the first use of the component " That indeed contradicts the proposal, however I have formed the proposal entirely based on your input to the issue on 5th of October, where you have stated explicitly : "If the reference has a multiplicity of 1..1 or 1..n, then such an unresolved reference should generate a deployment error." You got me there. I guess I didn't concentrate very closely before on deploy vs. runtime for this error. Maybe I have misunderstood you & the intention for 0..1, sorry for that , but that only shows that the issue is valid and it needs clarification :). I personally believe that the initial suggestion based on your email (deployment exception for unwired reference with 1..1) is better for the assembler who is alarmed immediately of wiring problems at deployment, instead of deferring them to the first runtime invocation. Often applications are complex and the assembler would have very hard time verifying each possible path of the business logic (full cyclomatic complexity search) to check for such unwired references and whether everything is working. That feature at least to me seems more valuable than covering the use case of having A wired to B via reference X with 1..1, B wired to A via reference Y with 1..1, A is deployed as single contribution, afterwards B is deployed as single contribution. In addition if we delay the exception at runtime in the 1..1 case, I am still lost what exactly is the difference between 0..1 and 1..1. In both cases we will allow deployment if there is no target for the reference, in both cases there will be exception at runtime if the target is still not available, and in both cases if there is target the call will pass. The difference is that in the 1..1 case the error will be raised on the first use of the component, not on the first use of that reference (that way you don't have to wait until the reference is used before getting your NullPointerException, or whatever it is). I'd be OK with generating the error at deployment time if we invented some means of doing batch deployment - to tell the system not to do its checks until a group of related deployments are all complete. However, writing up such a mechanism would be a bit more work. Back to some other raised issues and raised points: - I have changed the first sentence in the way you have suggested, also specified that it's neither in runtime nor in deployment there will be errors. Thanks for the suggestion Great. - The MUST in the last sentence is not bringing enough information, very good point. I switched it to use "will be represented" and added mentioning of the extensibility hooks. I like that. So here is the new PROPOSAL : I like the new proposal, except the fact that it creates a need for some kind of bulk deployment mechanism, as noted above. Michael The following description should be added in section 1.6.2 References, after line 1387 (that line is after the paragraph that explains attaching a binding to a reference and before the paragraph explaining callback) : Promotion of references accessing endpoints via bindings is suggested practice since it allows the assembler to change the targets of the references or the specified bindings and encourages component reuse, however the lack of such promotion by itself MUST NOT cause errors during deployment or runtime if the target of the reference can be identified. The assembler is expected to guarantee for an unpromoted reference with multiplicity 1..1 or 1..n that one of the following conditions holds : there is either internal wire within the scope of the current composite or a binding that identifies correctly either the component/service for a wire to an endpoint within the SCA domain or the accessible address of some endpoint outside the SCA domain. If the assembler does not provide these conditions for a reference that has a multiplicity of 1..1 or 1..n, then such an unresolved reference MUST generate a deployment error. If the assembler does not provide these conditions for a reference that has a multiplicity with 0..1 or 0..n , then the programming model MUST not generate deployment errors and the reference's wiring state will be represented in accordance to the implementation type in question (e.g. null, handle that throws exceptions when accessed, extensibility hooks, etc.). For example the following definitions MUST NOT generate deployment error : <composite xmlns="http://www.osoa.org/xmlns/sca/1.0" name="MyValueComposite"> <component name="MyValueServiceComponent"> <implementation.java class="services.myvalue.MyValueServiceImpl"/> <reference name="StockQuoteService"> <binding.ws uri=",http://www.sqs.com/StockQuoteService"/> </reference> <reference name="StockQuoteService2"> <binding.jms> <destination name="StockQuoteServiceQueue"/> <connectionFactory name="StockQuoteServiceQCF"/> </binding.jms> </reference> </component> <!-- no references and promotion on purpose --> <composite> however the following definitions MUST generate one : <composite xmlns="http://www.osoa.org/xmlns/sca/1.0" name="MyValueComposite"> <component name="MyValueServiceComponent"> <implementation.java class="services.myvalue.MyValueServiceImpl"/> <reference name="UnwiredReference"> <!-- the target cannot be determined, thatshouldbean error--> <binding.ws/> </reference> </component> <!-- no references and promotion on purpose --> <composite> Best Regards Peter From: Martin Chapman [mailto:martin.chapman@oracle.com] Sent: Wednesday, 24. October 2007 19:24 To: Blohm, Henning; 'Michael Rowley'; 'OASIS Assembly' Subject: RE: [sca-assembly] ISSUE 6: usage of not promoted references do i smell some confromance targets here...what do we (abstractly) install and to what, and where do we deploy it? -----Original Message----- From: Blohm, Henning [mailto:henning.blohm@sap.com] Sent:, Wednesday, October 24, 2007 4:46 PM To: Michael Rowley; OASIS Assembly Subject: AW: [sca-assembly] ISSUE 6: usage of not promoted references Michael, on the deployment error issue. In SCA we seemed to use the term deployment as "making available to process requests" and used the additional term "installation" for getting something into the system. Reading deployment as "making available to process requests" it is very close to "use" in which case you and Peter seem to talk about the same point in time. It could be best if the assembly spec would include some wording to describe the exact meaning of "deploy" and "install". You agree? Thanks, Henning Von: Michael Rowley [mailto:mrowley@bea.com] Gesendet: Mittwoch, 24. Oktober 2007 15:28 An: OASIS Assembly Betreff: RE: [sca-assembly] ISSUE 6: usage of not promoted references [MR: inline] -----Original Message----- From: Peshev, Peter [mailto:peter.peshev@sap.com] Sent: Wednesday, October 24, 2007 3:26 AM To: Michael Rowley; OASIS Assembly Subject: RE: [sca-assembly] ISSUE 6: usage of not promoted references HI Michael, Comments inline, I have pasted your issues with ">" >- First, "RECOMMENDED" and "NOT REQUIRED" are not a defined keywords. PP : There is no ""RECOMMENDED" in this proposal. In addition when looking at http://www.ietf.org/rfc/rfc2119.txt RECOMMENDED and REQUIRED are mentioned as key words. [MR: Good point on RECOMMENDED (I had originally written just "NOT REQUIRED", but then belatedly (and incorrectly) added "RECOMMENDED" when I happened to see it - apparently when I was looking too far down in the email to the old proposal). Regarding "NOT REQUIRED" - yes "REQUIRED" is a keyword, and "MUST NOT" is also a key phrase, but "NOT REQUIRED" is not.] Anyway as per the notes of the OpenCSA Steering Committee Minutes from 28 September the keyword SHOULD and its synonym RECOMMENDED are supposed to be avoided, and only the rest of the keywords remain to be used. However being a developer I don't claim any competence in speac creation, so maybe you are right. > In particular, the bit that says that "an implementation which does not include a particular option MUST be prepared to interoperate with ...". What does that mean when the "implementation" is the assembler? PP : At least my understanding of the keyword usage is that they should be used whenever there is requirement towards the SCA Runtime (i.e. the vendors that will implement the spec), and not to be used for any users of the spec -- assembler, deployer, etc. That's what was supposed to be in the proposal, If something is not done in that way, I will be glad to fix. if the first sentence is not clear enough, maybe we can adapt it to : Promotion of references accessing endpoints via bindings is common practice since it allows the assembler to change the targets of the references or the specified bindings and encourages component reuse,: however the lack of such promotion MUST NOT cause error in SCA Runtime-s . [MR: I think it is worthwhile to say that promotion is recommended (lowercase). I think it is very valuable for the specification to include directives and suggestions to our various human roles. Changing the MUST NOT to be on the runtime seems better, but perhaps it should be on deployment, as in "lack of promotion MUST NOT cause an error during deployment."] >- I suspect that we should not REQUIRE that a deployment error be generated for unwired 1..1 references. Consider what would happen if someone developed deployable composites A and B (each from different contributions) with the intention of wiring at least one of the components from A to something in B and wiring at least one component in B to something in A. There would be no legal ordering of the deployments, as the first deployment would always fail. PP : Yes, it will be an error. In that case the assembler should use 0..1 if he wants to deploy the first component and after some time the other. Isn't this exactly what 0..1 was intended for ? Otherwise what is the difference between 0..1 and 1..1 ? [MR: Having 1..1 instead of 0..1 could mean that an error should be generated at runtime, possibly at the first use of the component that includes that reference, rather than at deployment time. It would be unfortunate for someone to have to declare a reference that is really required as 0..1 just to get around deployment order issues.] >- The last MUST, which is on the programming model, says: "MUST represent the reference's wiring state in accordance to the implementation type in question". Presumably Peter meant to include the words "as invalid" after the word "state". However, even with this modification I don't like the requirement. SCA is intended to be an integration technology, which means that it needs to be able to accommodate a wide variety of implementation types. Some of these implementation types will use programming models where external services can be used, but some kind of default behavior occurs if one isn't (think of extensibility hooks). Such a programming model should be able to represent these as references to SCA, in spite of the fact that they don't follow the admonition that unwired references be presented as nulls. PP : The wording "according to the implementation type in question" was supposed to cover the "wide variety of implementation types" that you are speaking. If you prefer some other wording I would be glad to include. Maybe mentioning explicitly extensibility hooks if you consider them so important : ... MUST NOT generate deployment errors and MUST represent the reference's wiring state in accordance to the implementation type in question (e.g. null, handle that throws exceptions when accessed, extensibility hooks, etc.). [MR: I was reacting against this on the assumption, apparently incorrect, that the words "as invalid" had been removed accidentally, since the current sentence doesn't seem to make any sense. I read the current wording as saying "the programming model MUST represent the reference however it wants." What kind of a requirement is that?]] Michael Best Regards Peter ________________________________ From: Michael Rowley [mailto:mrowley@bea.com] Sent: Tuesday, 23. October 2007 20:54 To: Peshev, Peter; OASIS Assembly Subject: RE: [sca-assembly] ISSUE 6: usage of not promoted references I'll comment on the RFC 2119 usage, which I had hoped to avoid, but I we, have to address it at some point, so we might as well start with this proposal. - First, "RECOMMENDED" and "NOT REQUIRED" are not a defined keywords. If we changed it to use the closest defined keyword ("MAY") it might be something like "The assembler MAY promote references...", but that would, be odd, given the definition of MAY according to 2119:. 5. MAY This word, or the adjective "OPTIONAL", mean that an item is truly optional. One vendor may choose to include the item because a particular marketplace requires it or because the vendor feels that it enhances the product while another vendor may omit the same item. An implementation which does not include a particular option MUST be prepared to interoperate with another implementation which does include the option, though perhaps with reduced functionality. In the, same vein an implementation which does include a particular option MUST be prepared to interoperate with another implementation which does not include the option (except, of course, for the feature the option provides.) In particular, the bit that says that "an implementation which does not include a particular option MUST be prepared to interoperate with ...". What does that mean when the "implementation" is the assembler? - I suspect that we should not REQUIRE that a deployment error be generated for unwired 1..1 references. Consider what would happen if someone developed deployable composites A and B (each from different contributions) with the intention of wiring at least one of the components from A to something in B and wiring at least one component in, B to something in A. There would be no legal ordering of the deployments, as the first deployment would always fail. - The last MUST, which is on the programming model, says: "MUST represent the reference's wiring state in accordance to the implementation type in question". Presumably Peter meant to include the, words "as invalid" after the word "state". However, even with this modification I don't like the requirement. SCA is intended to be an integration technology, which means that it needs to be able to accommodate a wide variety of implementation types. Some of these implementation types will use programming models where external services, can be used, but some kind of default behavior occurs if one isn't (think of extensibility hooks). Such a programming model should be able, to represent these as references to SCA, in spite of the fact that they don't follow the admonition that unwired references be presented as nulls. Michael -----Original Message----- From: Peshev, Peter [mailto:peter.peshev@sap.com] Sent: Tuesday, October 23, 2007 12:31 PM To: OASIS Assembly Subject: RE: [sca-assembly] ISSUE 6: usage of not promoted references Once again, replacing the funny idea of : "reference with reference 1..1 or 1..n" with the intended wording. Otherwise everything is the same. Sorry :( PROPOSAL : The following description should be added in section 1.6.2 References, after line 1387 (that line is after the paragraph that explains attaching a binding to a reference and before the paragraph explaining callback) : Promotion of references accessing endpoints via bindings is common practice since it allows the assembler to change the targets of the references or the specified bindings and encourages component reuse, however it is NOT REQUIRED. The assembler is expected to guarantee for an unpromoted reference with multiplicity 1..1 or 1..n that one of the following conditions holds : there is either internal wire within the scope of the current composite or a binding that identifies correctly either the component/service for a wire to an endpoint within the SCA domain or the accessible address of some endpoint outside the SCA domain. If the assembler does not provide these conditions for a reference that has a multiplicity of 1..1 or 1..n, then such an unresolved reference MUST generate a deployment error. If the assembler does not provide these conditions for a reference that has a multiplicity with 0..1 or 0..n , then the programming model MUST not generate deployment errors and MUST represent the reference's wiring state in accordance to the implementation type in question (e.g. null, handle that throws exceptions when accessed, etc.). For example the following definitions MUST NOT generate deployment error, : <composite xmlns="http://www.osoa.org/xmlns/sca/1.0" name="MyValueComposite"> <component name="MyValueServiceComponent"> <implementation.java class="services.myvalue.MyValueServiceImpl"/> <reference name="StockQuoteService">. <binding.ws uri="http://www.sqs.com/StockQuoteService"/> </reference> <reference name="StockQuoteService2"> <binding.jms> <destination name="StockQuoteServiceQueue"/> <connectionFactory name="StockQuoteServiceQCF"/> </binding.jms> </reference> </component> <!-- no references and promotion on purpose --> <composite> however the following definitions MUST generate one : <composite xmlns="http://www.osoa.org/xmlns/sca/1.0" name="MyValueComposite"> <component name="MyValueServiceComponent"> <implementation.java class="services.myvalue.MyValueServiceImpl"/> <reference name="UnwiredReference"> <!-- the target cannot be determined, that should be an, error--> <binding.ws/> </reference> </component> <!-- no references and promotion on purpose --> <composite> --------------------------------------------------------------------- To unsubscribe from this mail list, you must leave the OASIS TC that generates this mail. 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