[oslc-core] Unrecognized content
Steve K Speicher
sspeiche at us.ibm.com
Wed Oct 17 13:58:30 EDT 2012
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
> >
> >
> >
>
>
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