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Re: SDW plenary agenda item - Namespace for SOSA and SSN ontology

From: Clemens Portele <portele@interactive-instruments.de>
Date: Wed, 22 Feb 2017 12:54:12 +0000
To: Maxime Lefrançois <maxime.lefrancois@emse.fr>
CC: Armin Haller <armin.haller@anu.edu.au>, "janowicz@ucsb.edu" <janowicz@ucsb.edu>, Raphaël Troncy <raphael.troncy@eurecom.fr>, "public-sdw-wg@w3.org" <public-sdw-wg@w3.org>
Message-ID: <3E8CED05-1380-4DAA-8AFB-A22BFEF0C973@interactive-instruments.de>
Dear Maxime,

thank you for the explanations, they help to understand the one-namespace option.

Just one follow-up question. Currently the wiki explanation has the following for the one-namespace solution:

SOSA ontology:
...
unify:Platform rdf:type owl:Class ;
...

SSN ontology:
...
unify:Platform rdf:type owl:Class ;
...

"unify:Platform rdf:type owl:Class" in the SSN ontology (FULL) is not necessary and should be removed as the axiom is already imported from the SOSA ontology (CORE). Correct?

Thanks,
Clemens


On 22 Feb 2017, at 12:57, Maxime Lefrançois <maxime.lefrancois@emse.fr<mailto:maxime.lefrancois@emse.fr>> wrote:

Dear Clemens,

> If I take a term that is in both ontologies (e.g., I can see Sensor in both sosa.ttl > and ssn.ttl, with different properties), where does http://www.w3.org/ns/unify/TermInBothOntologies take me, the SOSA or the SSN ontology? I assume SOSA as the "core".

A term would be defined in at most one ontology, CORE or FULL.

Potentially, if this ontology is CORE, this term will be further axiomatized (not defined), in the ontology FULL.

So to answer your question, looking up URI http://www.w3.org/ns/unify/TermInBothOntologies would redirect you to CORE ontology if it is defined  in CORE.

> So, both ontologies would define a unify:TermInBothOntologies.

FULL imports CORE and  adds  axioms to its terms.
FULL does not "define" the terms that were already defined in CORE.

> If I look at the SSN ontology I would "see" a different unify:TermInBothOntologies than I see when looking at the SOSA ontology or when de-referencing the unify:TermInBothOntologies URI (which redirects to the SOSA ontology).

You would see the same resource identified  by the same, URI, but with additional information about it (axioms)


> If my understanding is correct, shouldn’t there be a constraint that the SSN ontology includes the SOSA definitions plus additional ones (at least for the SOSA terms that are included in SSN)?

This is very true, we model this with the owl:imports axiom. FULL imports CORE, hence every axiom that is in CORE is directly "imported" in FULL.


Is this approach common practice and will this be understood?

having an ontology O2 that imports another  ontology O1 and adds axioms to  the terms that are defined in O1 is common practice. See for instance SKOS and SKOS-XL.

on the other hand, what's new here is that the two ontologies share the same namespace. AFAIK, this technical solution has first been proposed for the modularized and versioned ontology developed during the ITEA2 SEAS project, whose core modules actually generalize the core of the SSN ontology:

See
Maxime Lefrançois, Jarmo Kalaoja, Takoua Ghariani, Antoine Zimmermann, The SEAS Knowledge Model, ITEA2 12004 Smart Energy Aware Systems Deliverable 2.2, Jan 2017 - http://www.maxime-lefrancois.info/docs/SEAS-D2_2-SEAS-Knowledge-Model.pdf


Did I answer your questions ?

Kind regard,
Maxime Lefrançois


Best regards,
Clemens



On 22 Feb 2017, at 03:39, Armin Haller <armin.haller@anu.edu.au<mailto:armin.haller@anu.edu.au>> wrote:

Krzysztof, thanks for pointing that out! That was indeed a mistake, it should have read sosa:Platform and ssn:System. There is no sosa:System in our current proposal. But tomorrow it is all about the vote on the mechanics of the namespace for SOSA and SSN.

On 22/2/17, 11:27 am, "Krzysztof Janowicz" <janowicz@ucsb.edu<mailto:janowicz@ucsb.edu>> wrote:

   Just to avoid confusion. Armin is talking about ssn:System, not
   sosa:System (which does not exist). The concept that does exist in SOSA
   is sosa:Platform.


   On 02/21/2017 03:56 PM, Armin Haller wrote:
Hi Raphaël,

Thanks for your comment! In fact, the wiki is so detailed on the mechanics is because we *only* want to vote on the mechanics of the namespace issue tomorrow. The classes/properties that are shown are only exemplative. We have separate issues around the Platform and System class (i.e. https://www.w3.org/2015/spatial/wiki/Platform). In fact, there is a sosa:System and all current proposals under consideration in the Platform/System issue do retain a sosa:System class in the core. Please do ignore the modelling of those classes for tomorrow’s vote.

Once we have come to a decision on the *mechanics* on how to deal with namespaces we can tackle the remaining issues with the architecture of the integration (see also https://www.w3.org/2015/spatial/wiki/Proposals_for_rewriting_SSN), i.e. essentially a decision on *reuse of classes/properties only in SSN* or *equivalence/subclass/-property relationships in SSN to SOSA classes/ property*.

Cheers,
Armin

On 22/2/17, 10:24 am, "Raphaël Troncy" <raphael.troncy@eurecom.fr<mailto:raphael.troncy@eurecom.fr>> wrote:

    Dear Armin, all,

If you have an opinion on this, please do have a close look at the two
options on our Wiki page that outline the implementation implications of
each option: https://www.w3.org/2015/spatial/wiki/NamespaceIssue


    I think that the two options are insufficiently described in order to
    make an informed decision (sections 3.1 and 3.2). There is a lot of text
    explaining the mechanics of content negotiation which is sort of obvious
    for anyone who is familiar with the linked data concepts. On the
    contrary, there is insufficient information on the bulk of the issue,
    i.e. what (concepts and properties) is defined where, what is re-used,
    what is being further defined with more axioms between SOSA and (new) SSN.

    In the current option 1, one can only see the definition of a
    sosa:Platform in the sosa namespace, while this concept is further
    axiomatized in ssn.ttl using the concept of ssn:System. Does this mean
    that there is no sosa:System?

    I wish that the wiki page was not distracted by all the mechanics of
    trivial content negotiation and linked data terms dereferencing, and
    instead, focus on what is defined where precisely and exhaustively.
    Best regards.

       Raphaël

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   --
   Krzysztof Janowicz

   Geography Department, University of California, Santa Barbara
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Received on Wednesday, 22 February 2017 12:55:21 UTC

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