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local vs global restrictions on properties - was RE: ssn "not machine readable"

From: <Simon.Cox@csiro.au>
Date: Thu, 19 May 2016 00:08:33 +0000
To: <kerry.taylor@anu.edu.au>, <janowicz@ucsb.edu>, <s.kolozali@surrey.ac.uk>
CC: <public-sdw-wg@w3.org>
Message-ID: <cc21c0e31e5544728d31d6b91ecc06c9@exch1-mel.nexus.csiro.au>
I have also encountered this issue in the context of revising OWL-Time.

The 2006 version has domain/range specified for almost properties.
This effectively prevents some useful predicates (e.g. :before, :after, :inside) from being reused in externally defined applications unless all the externally defined classes are sub-classed from :TemporalEntity (or more strictly, use of these properties would entail subsumption from :TemporalEntity).

In the OGC view of the world, features _have_ geometry properties, they are not subclassed from geometry classes. If we assume the same relationship with Temporal Entities, then we have to decouple temporal properties from only being associated with Temporal Entities.

I would propose to remove some of the global rdfs:domain restrictions in particular, and add local cardinality constraints instead (where they are not already present).

Simon


From: Kerry Taylor [mailto:kerry.taylor@anu.edu.au]
Sent: Wednesday, 18 May 2016 10:21 AM
To: janowicz@ucsb.edu; s.kolozali@surrey.ac.uk
Cc: public-sdw-wg@w3.org
Subject: RE: ssn "not machine readable"

I get this now. SSN as it is now, usually uses  “local” domain and range constraints (formulated as restrictions) instead of  “global “ ones (formulated using the rdfs:domain and rdfs:range) properties. I believe it is actually quite careful about constraining object properties properly (maybe even too careful) and does it in  a best practice machine-readable OWL style.

Personally, I very much support the SSN-as-it-is-now style of object property constraints, but I am aware of a growing trend to do it the other way in simple “linked-data” ontologies.  This article includes a brief rationale  http://www.cs.vu.nl/~guus/public/owl-restrictions/ for the SSN “local” way.

This deserves more thought as part of the “simplification” and “modularisation” and “RDFS core” discussions…
Kerry




From: Krzysztof Janowicz [mailto:janowicz@ucsb.edu]
Sent: Wednesday, 18 May 2016 8:54 AM
To: s.kolozali@surrey.ac.uk<mailto:s.kolozali@surrey.ac.uk>; Kerry Taylor <kerry.taylor@anu.edu.au<mailto:kerry.taylor@anu.edu.au>>
Cc: public-sdw-wg@w3.org<mailto:public-sdw-wg@w3.org>
Subject: Re: ssn "not machine readable"

Hi,

I do not understand how the lack of global domain and range restrictions make SSN not machine readable. Also, there are many good reasons not to include global range and domain restrictions (and for adding guarded restrictions instead).

Best,
Krzysztof

On 05/17/2016 03:39 PM, s.kolozali@surrey.ac.uk<mailto:s.kolozali@surrey.ac.uk> wrote:
Hi Kerry,

    This was a problem that I had faced when I had to parse and map the SSN ontology (along with a many other ontologies) into SAOPY library that I have developed (http://iot.ee.surrey.ac.uk/citypulse/ontologies/sao/saopy.html). What I observed back then was the SSN ontology was missing all the domain and range restrictions for object properties. I had stated this problem to you in an e-mail and you had told me that it was simply due to the fact that "SSN ontology is using global restrictions instead of local restrictions". To solve this issue, I had to add all the domain and range restrictions of object properties one by one by going through and reading the comments in the SSN ontology. I am happy to send my local SSN copy to you "if you are interested in", which can save you a lot of time.

An excerpt the SSN ontology:
    <!-- http://purl.oclc.org/NET/ssnx/ssn#detects -->

    <owl:ObjectProperty rdf:about="&ssn;detects">
        <rdfs:label>detects</rdfs:label>
        <rdfs:seeAlso>http://www.w3.org/2005/Incubator/ssn/wiki/SSN_Skeleton#Skeleton</rdfs:seeAlso>
        <rdfs:comment>A relation from a sensor to the Stimulus that the sensor can detect.
The Stimulus itself will be serving as a proxy for (see isProxyOf) some observable property.</rdfs:comment>
        <rdfs:isDefinedBy>http://purl.oclc.org/NET/ssnx/ssn</rdfs:isDefinedBy>
    </owl:ObjectProperty>


An excerpt from my local copy of the SSN ontology:
    <!-- http://purl.oclc.org/NET/ssnx/ssn#detects -->

    <owl:ObjectProperty rdf:about="&ssn;detects">
        <rdfs:label>detects</rdfs:label>
        <rdfs:seeAlso>http://www.w3.org/2005/Incubator/ssn/wiki/SSN_Skeleton#Skeleton</rdfs:seeAlso>
        <rdfs:comment>A relation from a sensor to the Stimulus that the sensor can detect.
The Stimulus itself will be serving as a proxy for (see isProxyOf) some observable property.</rdfs:comment>
        <rdfs:isDefinedBy>http://purl.oclc.org/NET/ssnx/ssn</rdfs:isDefinedBy>
        <rdfs:domain rdf:resource="&ssn;Sensor"/>
        <rdfs:range rdf:resource="&ssn;SensorInput"/>
        <rdfs:range rdf:resource="&ssn;Stimulus"/>
    </owl:ObjectProperty>

Although it sounds like a fairly simple and straight forward issue, it causes lots of issues when one attempts to parse and use the SSN ontology in an automated way. The text written in the form of rdfs:comments are helpful for people but local restrictions are more helpful for machine interpretation.

Cheers,

Sefki Kolozali
Research Fellow
Institute for Communication Systems (ICS), home of the 5G Innovation Centre
University of Surrey
Guildford, Surrey, GU2 7XH, United Kingdom
Tel: +44 (0)1483 689490

E-mail: s.kolozali@s<mailto:s.kolozali@qmul.ac.uk>urrey.ac.uk<http://urrey.ac.uk>
http://www.surrey.ac.uk/ics/<http://www.surrey.ac.uk/ccsr/>





On 17 May 2016, at 23:11, Kerry Taylor <kerry.taylor@anu.edu.au<mailto:kerry.taylor@anu.edu.au>> wrote:

Hi Sefki,

Can you please explain further what you meant about failure of  “machine readability” with ssn as raised in the meeting today? Before that, can you do your test with this ssn herehttps://www.w3.org/ns/ssn/  as it seems likely to me that dul could have been the source of trouble and this is the new  (FPWD) version with dul removed.

Kerry




--

Krzysztof Janowicz



Geography Department, University of California, Santa Barbara

4830 Ellison Hall, Santa Barbara, CA 93106-4060



Email: jano@geog.ucsb.edu<mailto:jano@geog.ucsb.edu>

Webpage: http://geog.ucsb.edu/~jano/


Semantic Web Journal: http://www.semantic-web-journal.net

Received on Thursday, 19 May 2016 00:09:18 UTC

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