Re: [oslc-core] RE: OSLC Query Capability question

["Nicholas Crossley" <nick_crossley@us.ibm.com>]

OSLC has avoided use of RDF containers
and collections (List, Seq, Bag, and Alt). They complicate RDF representations
and queries, and there are often better ways to represent things. For example,
in most cases a simple repeated predicate is sufficient to represent a
set of elements. Ordering of elements can be done by the client using natural
properties of those elements.

For ordered query results, you are right
in that the repeated predicate used in OSLC query results (and elsewhere
in OSLC) does not by itself provide any ordering. We are in the process
of improving the OSLC query specification as part of OSCL 3.0 to address
this issue. The intent is that the oslc.order criteria implies that each
page of results must have query results that are correctly ordered with
respect to previous and subsequent pages, but does not imply anything about
the ordering of RDF triples within a single page. The client is expected
to be able to sort the results within a page according to its own requirements
- and should therefore include in oslc.select any attributes needed to
do that.

Nick.





From:      
 Jad El-Khoury <jad@kth.se>
To:      
 "oslc-core@lists.oasis-open.org"
<oslc-core@lists.oasis-open.org>
Cc:      
 Andrii Berezovskyi
<andriib@kth.se>, Axel Reichwein <axel.reichwein@koneksys.com>,
Ricardo Herrera <ricardo.herrera@koneksys.com>
Date:      
 08/31/2018 04:15 AM
Subject:    
   [oslc-core]
RE: OSLC Query Capability question
Sent by:    
   <oslc-core@lists.oasis-open.org>

---

Dear Core TC,
 
I am not sure if the Core TC is meant to
deal with public questions, but we got a question from Ricardo (Koneksys)
about the OSLC Query and I thought maybe someone from this TC can help?
Ricardo cannot directly send emails to
this mailing list. But I found the question interesting myself.
 
Anyone that can clarify how the reponse
for a query request with âoslc.orderâ meant to work?
 
regards
______________________________
Jad El-khoury, PhD
KTH Royal Institute of Technology
School of Industrial Engineering and Management,
Mechatronics Division
BrinellvÃgen 83, SE-100 44 Stockholm, Sweden
Phone: +46(0)8 790 6877 Mobile: +46(0)70
773 93 45
jad@kth.se,
https://www.kth.se/profile/jad
 
From: Ricardo Herrera [mailto:ricardo.herrera@koneksys.com]
Sent: Friday, 31 August 2018 01:57
To: oslc-core@lists.oasis-open.org
Cc: Andrii Berezovskyi <andriib@kth.se>; Jad El-Khoury <jad@kth.se>;
Axel Reichwein <axel.reichwein@koneksys.com>
Subject: OSLC Query Capability question

Good day, I'm implementing an OSLC adapter where I need to use the oslc.orderBy clause in a QueryCapability, I couldn't find in 2.0 spec (neither in 3.0) the standard way to keep the order of the members in the Query Resource representation.

 

This is what I could find in 2.0:

 

"The OSLC client then uses HTTP GET to request a Query Resource representation of the query results. The Query Resource representation will contain property values about the query and a collection of resources that match the query criteria."

 

This description does not mention any shape for the Query Resource representation and less for a given important order of the members. So far I've seen examples that uses this shape:

 

=====================================================
<http://example.com/services/requirements/query>
        a oslc:ResponseInfo;
        oslc:totalCount 3;
        rdfs:member
            <http://example.com/services/requirements/6802> ,
            <http://example.com/services/requirements/2875> ,
            <http://example.com/services/requirements/103> .
 
<http://example.com/services/requirements/6802>
        a oslc_rm:Requirement ;
        dcterms:title        "..." .
        dcterms:description  "..." ;
 
<http://example.com/services/requirements/2875>
        a oslc_rm:Requirement ;
        ...
 
<http://example.com/services/requirements/103>
        a oslc_rm:Requirement ;
        ...
=====================================================

 

However rdfs:member predicate is not enough to establish an order. OSLC 3.0 focus on the use of LDP containers but I think does not meet this requirement also. I was thinking the solution should be something like:

 

=====================================================
<http://example.com/services/requirements/query>
        a oslc:ResponseInfo;
        oslc:totalCount 3;
        oslc:members[ a rdf:Seq ; rdf:li <http://example.com/services/requirements/6802> ; rdf:li <http://example.com/services/requirements/2875>; rdf:li <http://example.com/services/requirements/103> ]
=====================================================

 

but I wanted to know whether you have something different to address this scenario that I missed.

 

 

Thanks in advance.

 

Regards,

Ricardo.