[oslc-cm] [oslc-core] Provided guidance for adding relationship labels
Andrew J Berner
ajberner at us.ibm.com
Wed Sep 1 10:36:28 EDT 2010
Let's be clear that there are two issues, in actuality unrelated, that got
"combined" to try to understand the original guidance:
1) Should link annotations (attributes on the link itself) have any
information "derived" from the target resource; for example, should you
"title" the link with the title of the resource? Jim, Arthur, and others
(including me if I had responded) would say "NO" because whatever that
information is when you start, it's likely to change and then the
annotation on the link is misleading.
2) Should a client cache a resource? Maybe--it may be up to the client to
care about whether it's fresh, or some standard HTTP constructs could be
used to tell if it's ok to use the cached copy.
The idea of caching came into this thread as a possibly related to the
"meaning" behind the link annotation, but any discussion of caching has to
be on its own merits, not related to link annotations (especially if the
"NO" is heeded for (1)).
Now, question--Jim you say that e-tag probably won't work. Why not? Are
you thinking about the issue that the OSLC resource may not in actuality be
a single file on the server, so how does the server maintain a meaningful
e-tag? That was discussed at one point in the AM workgroup I know. Has
that been further discussed? It seems like an issue that's both important
and hard.
Andy Berner
Lead Architect, ISV Technical Enablement and Strategy
IBM Rational Business Development
972 561-6599
ajberner at us.ibm.com
Ready for IBM Rational software partner program -
http://www.ibm.com/isv/rational/readyfor.html
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|Arthur Ryman <ryman at ca.ibm.com> |
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|oslc-cm at open-services.net, oslc-core at open-services.net, oslc-core-bounces at open-services.net |
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|09/01/2010 08:55 AM |
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|Re: [oslc-core] Provided guidance for adding relationship labels |
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Good point.
I wonder if it is then appropriate to provide some guidance on the use HTTP
cache control - i don't think etags will help here.
So, if a provider wants to cache some information about the object
resource, like the title (using Steve's example), that server should also
look for an Cache-Control header and then decide if it can cache the
information, and if it can, how long it can cache it. (this information can
also be stored in the reified statement).
while all this can be done, and presumably to address expected performance
issues, i still think the guidance should be to refrain from using link
annotations to describe information about the target (object), and instead
only use it to describe the link itself.
<jim/>
jim conallen
CAM Lead Architect
jconallen at us.ibm.com
Rational Software, IBM Software Group
(Embedded image moved to file: pic18631.gif)Inactive hide details for
Arthur Ryman ---08/31/2010 04:19:13 PM---Steve/James, There are standard
HTTP practices that describeArthur Ryman ---08/31/2010 04:19:13
PM---Steve/James, There are standard HTTP practices that describe how to
safely cache
From: Arthur Ryman <ryman at ca.ibm.com>
To: James Conallen/Philadelphia/IBM at IBMUS
Cc: oslc-cm at open-services.net, oslc-core at open-services.net,
oslc-core-bounces at open-services.net, Steve K Speicher/Raleigh/IBM at IBMUS
Date: 08/31/2010 04:19 PM
Subject: Re: [oslc-core] Provided guidance for adding relationship labels
Steve/James,
There are standard HTTP practices that describe how to safely cache
resources, and well-behaved clients (e.g. Web browsers) should use those.
OSLC clients should be well-behaved HTTP clients. This includes the use of
ETags, expiry dates, and HEAD requests.
Regards,
___________________________________________________________________________
Arthur Ryman, PhD, DE
Chief Architect, Project and Portfolio Management
IBM Software, Rational
Markham, ON, Canada | Office: 905-413-3077, Cell: 416-939-5063
Twitter | Facebook | YouTube
From:
James Conallen <jconallen at us.ibm.com>
To:
Steve K Speicher <sspeiche at us.ibm.com>
Cc:
oslc-cm at open-services.net, oslc-core at open-services.net
Date:
08/31/2010 03:29 PM
Subject:
Re: [oslc-core] Provided guidance for adding relationship labels
Sent by:
oslc-core-bounces at open-services.net
my 2c,
I worry about guidance that that suggests that it is ok to essentially
cache information about a resource that is being referenced (and managed
by) on another server. If this is to be a practice, what are the
recommendations for ensuring that this information remains in sync.
Looking at the referenced example, what happens if the owner of the
resource 123 changes its title to "Enhancement 123: Enable multi-root
installs"? Will this have to be manually updated? If not, does the system
automatically update properties of links whenever it detects them.
While I do recognize this may be a way to save a GET call. I don't think
it represents a best practice.
<jim/>
jim conallen
CAM Lead Architect
jconallen at us.ibm.com
Rational Software, IBM Software Group
Steve K Speicher---08/31/2010 02:47:42 PM---I wanted to call out some
specification updates that was created for handling of relationship label
From: Steve K Speicher/Raleigh/IBM at IBMUS
To: oslc-cm at open-services.net
Cc: oslc-core at open-services.net
Date: 08/31/2010 02:47 PM
Subject: [oslc-core] Provided guidance for adding relationship labels
Sent by: oslc-core-bounces at open-services.net
I wanted to call out some specification updates that was created for
handling of relationship labels on URI relationship properties. Note the
support for this is optional but wanted to make sure this was done in a
uniform way across implementations. Let me know if there are any issues
with this.
http://open-services.net/bin/view/Main/CmSpecificationV2#Labels_for_Relationships
Thanks,
Steve Speicher | IBM Rational Software | (919) 254-0645
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