[oslc-core] Issue 42 proposed resolution - UPDATED with language to remove error and add warning header

[Martin P Pain]

The text "The provider SHOULD NOT return an error (HTTP error status code 
or OSLC error resource) when unsupported search properties are present" is 
a little ambiguous - "The provider SHOULD NOT return an error (HTTP error 
status code or OSLC error resource) as a result of unsupported search 
properties being present" would be less so.

Martin




From:   Michael F Fiedler <fiedler at us.ibm.com>
To:     oslc-core at open-services.net, 
Date:   15/04/2013 18:15
Subject:        [oslc-core] Issue 42 proposed resolution - UPDATED with 
language to remove error and add warning header
Sent by:        "Oslc-Core" <oslc-core-bounces at open-services.net>



Revised proposed resolution for issue 42 which incorporates feedback from 
last week's Core workgroup meeting.   I am re-copying the issue summary 
here - proposed resolution wording follows.   The final two sentences are 
the changed content.

======  SUMMARY ========
Core issue #42 [1] deals with service provider behavior when a consumer 
requests selective properties or attempts to filter/search using 
properties not known to the provider.   The e-mail thread describes three 
variations on the issue:

1. Client requests selective properties (oslc.select/oslc.properties) 
defined as optional in the spec and which are not supported by the 
provider [1]
2. Client requests selective properties not defined in the specification 
[1]
3. Client tries to filter or search (oslc.where) using a property not 
supported by the provider [2]

The issue was discussed on-list, in early 2012 workgroup meetings and it 
appears some side meetings were held as well to investigate the behavior 
of existing implementations.   Based on the discussions, the following 
informative text is proposed for the Core specification.   The workgroup 
should discuss the content and whether it goes in V2 or is deferred to V3.

====== PROPOSED RESOLUTION =======
To be inserted as a new sub-heading under "Unknown Properties and Content" 
[3]

(This section is informative.)

A consumer can send an OSLC query with a request for selective properties 
(oslc.properties, oslc.select) which the provider does not recognize. 
These properties could be unsupported properties from an OSLC 
specification or properties not included in an OSLC specification.  When 
unsupported selective properties are present in an OSLC query, the 
provider is encouraged to ignore these properties and form the query 
response as if they were not present.  Other recognized selective 
properties on the query should be honored.

A consumer can send an OSLC query with a a request to search on specific 
properties (oslc.where) which the provider does not recognize.  These 
properties could be unsupported properties from an OSLC specification or 
properties not included in an OSLC specification.  When unsupported search 
properties are present, the provider is encouraged to follow the semantics 
of SPARQL WHERE as it relates to OSLC query (see: 
http://open-services.net/bin/view/Main/OslcSimpleQuerySparqlV1#Example_2_Searching_for_Resource
).  If the property is not present in the RDF graph of resources queried, 
no resources will match the query.   The provider SHOULD NOT return an 
error (HTTP error status code or OSLC error resource) when unsupported 
search properties are present.   The provider MAY include a standard HTTP 
Warning header in the response to indicate that a search property is not 
known or not supported. 


[1] - 
http://open-services.net/pipermail/oslc-core_open-services.net/2012-March/001257.html

[2] - 
http://open-services.net/pipermail/oslc-core_open-services.net/2012-April/001287.html

[3] - 
http://open-services.net/bin/view/Main/OslcCoreSpecification#Unknown_properties_and_content




Regards,
Mike

Michael Fiedler
IBM Rational Software
fiedler at us.ibm.com
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