[oslc-core] Unrecognized content
John Arwe
johnarwe at us.ibm.com
Tue Oct 30 09:25:58 EDT 2012
The additional MUST from Steve's change should probably be rolled into
not-finalized specs that have summarized Core requirements in a table ...
Automation, Performance Monitoring, Reconciliation at least ... so when
the next spec(s) come along and use them as examples, the change gets
propagated. Since the WG leads are on cc here, they can handle in the
respective specs.
Related note: I saw that the 'not' was neither capitalized nor bold. Since
the intent was I think obvious, I just fixed it now.
from: The Service SHOULD not return an error code for unrecognized
content.
to : The Service SHOULD NOT return an error code for unrecognized
content.
Best Regards, John
Voice US 845-435-9470 BluePages
Tivoli OSLC Lead - Show me the Scenario
"Oslc-Core" <oslc-core-bounces at open-services.net> wrote on 10/17/2012
01:58:30 PM:
> From: Steve K Speicher/Raleigh/IBM at IBMUS
> To: Oslc-Core at open-services.net
> Date: 10/17/2012 02:01 PM
> Subject: Re: [oslc-core] Unrecognized content
> Sent by: "Oslc-Core" <oslc-core-bounces at open-services.net>
>
> At first edit, missed Arthur's approved suggestion to "MUST". Fixed
that.
>
> Thanks,
> Steve Speicher
> IBM Rational Software
> OSLC - Lifecycle integration inspired by the web ->
> http://open-services.net
>
> "Oslc-Core" <oslc-core-bounces at open-services.net> wrote on 10/17/2012
> 10:03:40 AM:
>
> > From: Steve K Speicher/Raleigh/IBM at IBMUS
> > To: Oslc-Core at open-services.net,
> > Date: 10/17/2012 10:12 AM
> > Subject: Re: [oslc-core] Unrecognized content
> > Sent by: "Oslc-Core" <oslc-core-bounces at open-services.net>
> >
> > I have incorporated this change with slight editorial changes [1].
> > This closes Issue-16 [2]
> >
> > [1] -
> http://open-services.net/bin/view/Main/OslcCoreSpecification?rev=72
> > [2] - http://open-services.net/wiki/core/OSLC-Core-V2-Issues/
> >
> > Thanks,
> > Steve Speicher
> > IBM Rational Software
> > OSLC - Lifecycle integration inspired by the web ->
> > http://open-services.net
> >
> > Arthur Ryman <ryman at ca.ibm.com> wrote on 09/23/2012 09:40:41 PM:
> >
> > > From: Arthur Ryman <ryman at ca.ibm.com>
> > > To: James Conallen/Philadelphia/IBM at IBMUS,
> > > Cc: Oslc-Core at open-services.net,
oslc-core-bounces at open-services.net,
> > Steve
> > > K Speicher/Raleigh/IBM at IBMUS
> > > Date: 09/23/2012 09:40 PM
> > > Subject: Re: [oslc-core] Unrecognized content
> > >
> > > Jim,
> > >
> > > +1 except for stronger wording about errors:
> > >
> > > A Service provider MUST return an error code if recognized content
is
> > > invalid.
> > >
> > > Regards,
> > >
> >
>
___________________________________________________________________________
>
> >
> > >
> > > Arthur Ryman
> > >
> > > DE, Chief Architect, Reporting &
> > > Portfolio Strategy and Management
> > > IBM Software, Rational
> > >
> > > Toronto Lab | +1-905-413-3077 (office) | +1-416-939-5063 (mobile)
> > >
> > >
> > >
> > >
> > >
> > > From:
> > > James Conallen <jconallen at us.ibm.com>
> > > To:
> > > Steve K Speicher <sspeiche at us.ibm.com>
> > > Cc:
> > > Oslc-Core at open-services.net, oslc-core-bounces at open-services.net
> > > Date:
> > > 09/18/2012 09:16 AM
> > > Subject:
> > > Re: [oslc-core] Unrecognized content
> > > Sent by:
> > > oslc-core-bounces at open-services.net
> > >
> > >
> > >
> > > Ok, how about this update for the Unknown properties and content
> > section:
> > >
> > > For OSLC Defined Resources, clients SHOULD assume that an OSLC
Service
>
> > > will discard unknown property values. An OSLC Service MAY discard
> > property
> > > values that are not part of the resource definition or Resource
Shape
> > > known by the server. If a client needs verification that the
> requested
> > > update was accepted it SHOULD note the ETag returned with the PUT,
> then
> > > immediately GET the resource back and compare the ETag and contents
> with
> >
> > > its expectations. The Service SHOULD not return an error code for
> > > unrecognized content. A Service provider MAY return an error code
if
> > > recognized content is invalid.
> > >
> > > The rule is different for clients. When doing an update, OSLC
clients
> > MUST
> > > preserve any unknown property-values and other content in OSLC
Defined
>
> > > Resources.
> > >
> > >
> > > Thanks,
> > >
> > > jim conallen
> > > Rational Design Management (DM) Integration Architect, OSLC AM Lead
> > > jconallen at us.ibm.com
> > > Rational Software, IBM Software Group
> > >
> > >
> > >
> > > Steve K Speicher---09/18/2012 08:51:25 AM---+1 We are saying it can
> > > happen, we just need a proposal for how clients can learn this. We
> > > require
> > >
> > > From: Steve K Speicher/Raleigh/IBM at IBMUS
> > > To: Oslc-Core at open-services.net,
> > > Date: 09/18/2012 08:51 AM
> > > Subject: Re: [oslc-core] Unrecognized content
> > > Sent by: oslc-core-bounces at open-services.net
> > >
> > >
> > >
> > > +1 We are saying it can happen, we just need a proposal for how
> clients
> > > can learn this. We require a round trip now: PUT, GET, then check.
> > >
> > > Steve Speicher
> > > IBM Rational Software
> > > OSLC - Lifecycle integration inspired by the web ->
> > > http://open-services.net
> > >
> > > > From: Arthur Ryman <ryman at ca.ibm.com>
> > > > To: James Conallen/Philadelphia/IBM at IBMUS,
> > > > Cc: Oslc-Core at open-services.net, Adam Neal <Adam_Neal at ca.ibm.com>,
> > oslc-
> > > > core-bounces at open-services.net
> > > > Date: 09/14/2012 01:59 PM
> > > > Subject: Re: [oslc-core] Unrecognized content
> > > > Sent by: oslc-core-bounces at open-services.net
> > > >
> > > > Jim,
> > > >
> > > > I think we may be stretching the analogy here.
> > > >
> > > > I am OK with you proposal: "I am ok if we just state that this
> > scenario
> > > > can happen, and that the client is responsible for determining if
> the
> > > > update was successful (from its view) by GETing the representation
> > > > immediately after and checking the content and comparing the
ETags."
> > > >
> > > > Pls draft some text and say where it should be included so we have
a
>
> > > > concrete proposal on the table.
> > > >
> > > > Regards,
> > > >
> > >
> >
>
___________________________________________________________________________
>
> >
> > >
> > >
> > > >
> > > > Arthur Ryman
> > > >
> > > > DE, Chief Architect, Reporting &
> > > > Portfolio Strategy and Management
> > > > IBM Software, Rational
> > > >
> > > > Toronto Lab | +1-905-413-3077 (office) | +1-416-939-5063 (mobile)
> > > >
> > > >
> > > >
> > > >
> > > >
> > > > From:
> > > > James Conallen/Philadelphia/IBM at IBMUS
> > > > To:
> > > > Arthur Ryman/Toronto/IBM at IBMCA
> > > > Cc:
> > > > Adam Neal <Adam_Neal at ca.ibm.com>, Oslc-Core at open-services.net,
> > > > oslc-core-bounces at open-services.net
> > > > Date:
> > > > 09/13/2012 04:44 PM
> > > > Subject:
> > > > Re: [oslc-core] Unrecognized content
> > > >
> > > >
> > > > Arthur,
> > > >
> > > > While I am not advocating that we respond with a 4xx when the
server
>
> > > does
> > > > not update a resource at a client's request. I point it out as an
> > > example
> > > > of how even RFC2616 requires some interpretation in context.
> > > >
> > > > What I do want to do is address this very real problem (that DM
and
> > RRC
> > > > are experiencing) that clients have when attempting to update
> > resources
> > > > (in general).
> > > >
> > > > Using your own Java analogy, a program that essentially is
> > > >
> > > > x = -42;
> > > > out.println( x );
> > > >
> > > > where the output is +42, because this particular type of variable
> only
> >
> > > > understands positive integers, and the programmer doesn't know
this.
>
> > Now
> > >
> > >
> > > > he is forced to check every time he makes an assignment before
> > > proceeding
> > > > with the program
> > > >
> > > > x = -42;
> > > > if( x != -42 ) throw exception
> > > >
> > > > I think because the OSLC explicitly says that the server can
ignore
> > > > unrecognized content, and there is no guaranteed way for a client
to
>
> > > know
> > > > what content the server recognizes, the onus is on the client to
be
> > > > responsible for checking the results. I think we should provide
> some
> > > > guidance and raise awareness of this scenario in our specs
> > > > (non-normatively), so client developers can be prepared for this
> > > > situation.
> > > >
> > > > I am ok if we just state that this scenario can happen, and that
the
>
> > > > client is responsible for determining if the update was successful
> > (from
> > >
> > >
> > > > its view) by GETing the representation immediately after and
> checking
> > > the
> > > > content and comparing the ETags.
> > > >
> > > >
> > > > Thanks,
> > > >
> > > > jim conallen
> > > > Rational Design Management (DM) Integration Architect, OSLC AM
Lead
> > > > jconallen at us.ibm.com
> > > > Rational Software, IBM Software Group
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > > From: Arthur Ryman/Toronto/IBM at IBMCA
> > > > To: James Conallen/Philadelphia/IBM at IBMUS,
> > > > Cc: Adam Neal <Adam_Neal at ca.ibm.com>,
> Oslc-Core at open-services.net,
> >
> > > > oslc-core-bounces at open-services.net
> > > > Date: 09/13/2012 04:03 PM
> > > > Subject: Re: [oslc-core] Unrecognized content
> > > >
> > > >
> > > > Jim,
> > > >
> > > > I disagree. The server ignored the content it didn't understand
and
> > did
> > > > the update, but the before and after state was the same. According
> to
> > > your
> > > > proposal, if I did a GET and then immediately PUT the resource,
that
>
> > > > should also result in an error because nothing changed. That would
> not
> >
> > > be
> > > > reasonable.
> > > >
> > > > Consider the following Java program:
> > > >
> > > > int x = 42;
> > > > x = 42;
> > > >
> > > > That shouldn't result in a compiler error.
> > > >
> > > > In fact, the behavior of the server is somewhat undefined if a PUT
> > would
> > >
> > >
> > > > result in no change to the resource. The server could try to be
> clever
> >
> > > and
> > > > only update the resource if some property changed. Or it could
take
> > the
> > > > request literally and replace the resource with an identical copy,
> but
> >
> > > as
> > > > a side affect, the modification date of the resource might change.
> > > >
> > > >
> > > > Regards,
> > > >
> > >
> >
>
___________________________________________________________________________
>
> >
> > >
> > >
> > > >
> > > > Arthur Ryman
> > > >
> > > > DE, Chief Architect, Reporting &
> > > > Portfolio Strategy and Management
> > > > IBM Software, Rational
> > > >
> > > > Toronto Lab | +1-905-413-3077 (office) | +1-416-939-5063 (mobile)
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > > From:
> > > > James Conallen/Philadelphia/IBM at IBMUS
> > > > To:
> > > > Arthur Ryman <ryman at ca.ibm.com>
> > > > Cc:
> > > > Adam Neal <Adam_Neal at ca.ibm.com>, Oslc-Core at open-services.net,
> > > > oslc-core-bounces at open-services.net
> > > > Date:
> > > > 09/07/2012 11:16 AM
> > > > Subject:
> > > > Re: [oslc-core] Unrecognized content
> > > >
> > > >
> > > > Hey Arthur,
> > > >
> > > > The spec for the PUT method says:
> > > >
> > > > If an existing resource is modified, either the 200 (OK) or 204
(No
> > > > Content) response codes SHOULD be sent to indicate successful
> > completion
> > >
> > >
> > > > of the request. If the resource could not be created or modified
> with
> > > the
> > > > Request-URI, an appropriate error response SHOULD be given that
> > reflects
> > >
> > >
> > > > the nature of the problem.
> > > >
> > > > In this scenario the server did not modify the resource, because
it
> > > didn't
> > > > recognize the content. So according to RFC 2616 we should be
> > returning
> > > an
> > > > error response.
> > > >
> > > >
> > > > Thanks,
> > > >
> > > > jim conallen
> > > > Rational Design Management (DM) Integration Architect, OSLC AM
Lead
> > > > jconallen at us.ibm.com
> > > > Rational Software, IBM Software Group
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > > From: Arthur Ryman <ryman at ca.ibm.com>
> > > > To: James Conallen/Philadelphia/IBM at IBMUS,
> > > > Cc: Adam Neal <Adam_Neal at ca.ibm.com>,
> Oslc-Core at open-services.net,
> >
> > > > oslc-core-bounces at open-services.net
> > > > Date: 09/07/2012 10:15 AM
> > > > Subject: Re: [oslc-core] Unrecognized content
> > > >
> > > >
> > > >
> > > > -1 for the 400 response code
> > > >
> > > > Jim, I don't understand what you are asking for. The spec already
> > makes
> > > it
> > > >
> > > > clear that the server will discard unrecognized content. The
client
> > > should
> > > >
> > > > expect that. What aspect of behavior is unclear?
> > > >
> > > > Regards,
> > > >
> > >
> >
>
___________________________________________________________________________
>
> >
> > >
> > >
> > > >
> > > >
> > > > Arthur Ryman
> > > >
> > > > DE, Chief Architect, Reporting &
> > > > Portfolio Strategy and Management
> > > > IBM Software, Rational
> > > >
> > > > Toronto Lab | +1-905-413-3077 (office) | +1-416-939-5063 (mobile)
> > > >
> > > >
> > > >
> > > >
> > > >
> > > > From:
> > > > James Conallen <jconallen at us.ibm.com>
> > > > To:
> > > > Oslc-Core at open-services.net
> > > > Cc:
> > > > Adam Neal/Ottawa/IBM at IBMCA
> > > > Date:
> > > > 09/07/2012 09:03 AM
> > > > Subject:
> > > > [oslc-core] Unrecognized content
> > > > Sent by:
> > > > oslc-core-bounces at open-services.net
> > > >
> > > >
> > > >
> > > > In the current specification we have the statement:
> > > > For OSLC Defined Resources, clients SHOULD assume that an OSLC
> Service
> >
> > > > will discard unknown property values. An OSLC Service MAY discard
> > > property
> > > >
> > > > values that are not part of the resource definition or Resource
> Shape
> > > > known by the server.
> > > >
> > > > We are running into a problem. When a client (in this case another
> > > > application server) PUTs an update to a resource that includes a
> > 'link'
> > > to
> > > >
> > > > another OSLC resource, and the server, at the time does not
> recognize
> > > the
> > > > link type, the link is not accepted, but a 200 OK is returned. The
> > > server
> > > >
> > > > returns a 200 OK, because it feels like it can ignore the
> unrecognized
> >
> > > > link. The client gets that 200 OK, and thinks that the link was
> > > > successfully added.
> > > >
> > > > This doesn't feel right. The only way a client can be sure that
the
>
> > PUT
> > >
> > >
> > > > worked as expected is to re-GET the resource and compare it to
what
> it
> >
> > > > expected to see (with the new link included), and maybe do a
little
> > > > looking at ETags to make sure things haven't changed in between.
> > > >
> > > > I guess the server could instead return a 400 Bad Request, and
> include
> >
> > > in
> > > > the response the reason for not accepting the PUT. But if the
> content
> >
> > > > that was submitted really should just be ignored (i.e. is part of
a
> > > future
> > > >
> > > > version of the resource), then we don't want to abort the update.
> > > >
> > > > The OSLC verbage does not provide any guidance as to what to do.
It
>
> > > would
> > > >
> > > > be helpful if we had more detailed explanation of this statement
in
> > the
> > > > spec.
> > > >
> > > >
> > > > Thanks,
> > > >
> > > > jim conallen
> > > > Rational Design Management (DM) Integration Architect, OSLC AM
Lead
> > > > jconallen at us.ibm.com
> > > > Rational Software, IBM Software Group
> > > > _______________________________________________
> > > > Oslc-Core mailing list
> > > > Oslc-Core at open-services.net
> > > >
> http://open-services.net/mailman/listinfo/oslc-core_open-services.net
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > > _______________________________________________
> > > > Oslc-Core mailing list
> > > > Oslc-Core at open-services.net
> > > >
> http://open-services.net/mailman/listinfo/oslc-core_open-services.net
> > > >
> > >
> > >
> > > _______________________________________________
> > > Oslc-Core mailing list
> > > Oslc-Core at open-services.net
> > >
http://open-services.net/mailman/listinfo/oslc-core_open-services.net
> > >
> > > _______________________________________________
> > > Oslc-Core mailing list
> > > Oslc-Core at open-services.net
> > >
http://open-services.net/mailman/listinfo/oslc-core_open-services.net
> > >
> > >
> > >
> >
> >
> > _______________________________________________
> > Oslc-Core mailing list
> > Oslc-Core at open-services.net
> > http://open-services.net/mailman/listinfo/oslc-core_open-services.net
> >
>
>
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