W3C home > Mailing lists > Public > public-sdw-wg@w3.org > January 2017

RE: State of SSN

From: Kerry Taylor <kerry.taylor@anu.edu.au>
Date: Mon, 30 Jan 2017 14:05:29 +0000
To: Rob Atkinson <rob@metalinkage.com.au>, "janowicz@ucsb.edu" <janowicz@ucsb.edu>, Armin Haller <armin.haller@anu.edu.au>, "Simon.Cox@csiro.au" <Simon.Cox@csiro.au>, "phila@w3.org" <phila@w3.org>, "public-sdw-wg@w3.org" <public-sdw-wg@w3.org>
CC: "ssimmons@opengeospatial.org" <ssimmons@opengeospatial.org>, "fd@w3.org" <fd@w3.org>
Message-ID: <SYXPR01MB1536D2FDFF06099E3C8B01CBA44B0@SYXPR01MB1536.ausprd01.prod.outlook.com>
Sorry rob – was distracted doing exactly that. (as I had promised) Please see https://www.w3.org/2015/spatial/wiki/Proposals_for_rewriting_SSN#Compromise_Proposal_6_made_by_Kerry_January_2017


The issue about the namespaces(s) is a little subtle.

We have many outstanding comments and requests from members asking why we need multiple namespaces – that has never been answered (I made a poor attempt at one of them, but that was because I was only repeating arguments that were made in spoken form to me alone). I don’t recall ever an argument being put to the group – or maybe I’ve forgotten it because it was so wrapped up in other  unstated assumptions about the integration architecture that I could not unpick.

For me --- if the architecture is done right I *think* but am not completely certain we need only one namespace. If we only need one then why have 2? Why has nobody followed up on Maxime’s presentation for example when he showed us how only one namespace is needed? Did we just ignore his trouble? I admit – I was technically challenged that particular meeting and could not follow well – but it seemed form the minutes like he had solved all the problems I have heard of. Maybe you can answer that question for me?

If I am appearing inconsistent here, then please forgive me in accepting the case for a namespace statement in the WD that was proposed in a very short timespace and if I had attempted to discuss it  (despite the implications for relevant outstanding issues that have never been addressed) I foresaw the WD being delayed yet again.  Please let me reiterate that under SOME potential integration architectures I would, on the other hand, insist on 2  namespaces anyway. E.g. architectures that allow sosa;Platform and ssn:Platform to mean different things both descriptively and axiomatically as we have right now on git but both being visible in ssn due to an import statement. If  this does not go away I will be arguing very strongly for divorce!


Ø  What seems to be the issue for you is whether SOSA reflects SSN requirements - and there seems to be a conflict between compatibility with the original SSN and the broader domain requirements?

I’m not sure I can answer that as posed. SOSA must be the core of ssn. Otherwise it has no function in our WD.  AS for requirements – we have a reposnibility to satisfy our use cases as well as we can – sosa has not even looked at the use cases wheras most (but not all)  are out of the box with ssn. I don’t think you are suggesting we reduce ssn  in order to to avoid satisfying our use cases?

Actually I see no compatibility conflicts prima facie –see my worked example for platform  for how such apparent conflicts can be resolved - although if you include the “alignment” as proposed last week then I retract that  statement in spades!


-Kerry

From: Rob Atkinson [mailto:rob@metalinkage.com.au]
Sent: Monday, 30 January 2017 7:03 PM
To: Kerry Taylor <kerry.taylor@anu.edu.au>; janowicz@ucsb.edu; Rob Atkinson <rob@metalinkage.com.au>; Armin Haller <armin.haller@anu.edu.au>; Simon.Cox@csiro.au; phila@w3.org; public-sdw-wg@w3.org
Cc: ssimmons@opengeospatial.org; fd@w3.org
Subject: Re: State of SSN

Kerry,
i'm not sure I can comprehend the objection regarding there being new namespace(s)  in the light of with what you wrote on the 2nd Jan:

"Note that http://w3c.github.io/sdw/ssn/ has been unchanged since 21 December, but there are two further changes decided in the meeting of 2016/12/20 that are yet to be pulled but are intended to be included, that is,

  *   Change backward compatibility ontology name ssn-bc to ssn-ssnxg and move to a w3c dated namespace
  *   Add a "namespace" paragraph in SOSA section, declaring http://www.w3.org/ns/sosa/"

Maybe I have misunderstood one or the other, but perhaps I wont be the only one in that boat.  Can you elucidate a counter proposal using concrete examples?

its possible to do everything in a single namespace, and use named graphs to partition the - but we seem to hit counter-intuitive behaviours of tools. Arguably a SSN ontology doesnt need a namespace - its defining behaviours on entities in the SOSA namespace.  What seems to be the issue for you is whether SOSA reflects SSN requirements - and there seems to be a conflict between compatibility with the original SSN and the broader domain requirements?


Rob

On Mon, 30 Jan 2017 at 18:07 Kerry Taylor <kerry.taylor@anu.edu.au<mailto:kerry.taylor@anu.edu.au>> wrote:
Actually there have been  several  emails on the list that disagree with this  statement (as presented in earlier times) And a presentation at an SSN meeting  on this topic too.

>  1) Regardless of what we call it there will be a new namespace

Those opinions have been  ignored and deserve listening to.

The “legacy SSN" case” is not an issue provided  the core is designed appropriately.  If there eis an “issue” it purely arises from the current core being designed independently of the ssn of which it is the core. Fixing this requires adjustment to both legacy ssn and the current version of the core.


Personally – I am unconvinced that multiple namespace have any purpose. Therefore , if there is no purpose, one namespace should be used.

> ) Where SSN needs to create specialisations it can subclass as required, in a new namespace - which can resolve to the SSN-2 graph

I am in violent disagreement with this statement., as I have said many times previously. Sorry to bore the list.



>  We also changed a few other axioms, e.g., on SubSystems.

I missed that entirely. When? Where?

--Kerry



From: Krzysztof Janowicz [mailto:janowicz@ucsb.edu<mailto:janowicz@ucsb.edu>]
Sent: Monday, 30 January 2017 5:29 PM
To: Rob Atkinson <rob@metalinkage.com.au<mailto:rob@metalinkage.com.au>>; Kerry Taylor <kerry.taylor@anu.edu.au<mailto:kerry.taylor@anu.edu.au>>; Armin Haller <armin.haller@anu.edu.au<mailto:armin.haller@anu.edu.au>>; Simon.Cox@csiro.au<mailto:Simon.Cox@csiro.au>; phila@w3.org<mailto:phila@w3.org>; public-sdw-wg@w3.org<mailto:public-sdw-wg@w3.org>

Cc: ssimmons@opengeospatial.org<mailto:ssimmons@opengeospatial.org>; fd@w3.org<mailto:fd@w3.org>
Subject: Re: State of SSN

Hi Rob,

1) Regardless of what we call it there will be a new namespace
2) SOSA contains the broad, inclusive, definitions for things we care about - i.e. it will be what lives behind that namespace URL and require no specific reasoning on the client side ("lightweight" to use)
3) SSN-2 can import and reference these SOSA entities and add additonal axioms (in a flavour of OWL with a specific expressivity which we should document the intent). (richer semantics but more demanding to use)
4) Where SSN needs to create specialisations it can subclass as required, in a new namespace - which can resolve to the SSN-2 graph
5) informative "Alignments" help others use and understand - but dont affect SOSA or SSN semantics - alignments with DUL and iso-19150 flavour O&M

Yes, great summary, this is very much what I believe we wanted to do since a long time. I think/hope we are all in violent agreement here :-).

All this is pretty straightforward IMHO until we hit the "legacy SSN" case

Oh yes...

My naive understanding is if we publish an alignment using strong axioms (equivalence or subclass?) then we are able to use original SSN deployments as evidence of implementation ... of the subset of semantics  - but we'd still need IMHO to demonstrate the broader sense and any new concepts. So its not trivial and we'd need a plan anyway - maybe its easier just to get someone to upgrade their legacy SSN to the new SOSA scope and namespace and show the broader definitions are usable directly.

I think we need new implementation evidence anyway due to the new namespace.  We cannot have equivalence classes between most old SSN and new SSN classes as the new classes lack DUL and so forth. We also changed a few other axioms, e.g., on SubSystems. I agree that this is the part that will need further strategizing and there will be no perfect solution.

Cheers,
Jano

On 01/29/2017 04:59 PM, Rob Atkinson wrote:

I think Kerry is correct to say we need to get on the same page with the "architecture" - and until we do that its hard to actually understand everybody's positions. Perhaps we focus on what that architecture means for users and the process?

Here's my understanding of that architecture:

1) Regardless of what we call it there will be a new namespace
2) SOSA contains the broad, inclusive, definitions for things we care about - i.e. it will be what lives behind that namespace URL and require no specific reasoning on the client side ("lightweight" to use)
3) SSN-2 can import and reference these SOSA entities and add additonal axioms (in a flavour of OWL with a specific expressivity which we should document the intent). (richer semantics but more demanding to use)
4) Where SSN needs to create specialisations it can subclass as required, in a new namespace - which can resolve to the SSN-2 graph
5) informative "Alignments" help others use and understand - but dont affect SOSA or SSN semantics - alignments with DUL and iso-19150 flavour O&M

All this is pretty straightforward IMHO until we hit the "legacy SSN" case

My naive understanding is if we publish an alignment using strong axioms (equivalence or subclass?) then we are able to use original SSN deployments as evidence of implementation ... of the subset of semantics  - but we'd still need IMHO to demonstrate the broader sense and any new concepts. So its not trivial and we'd need a plan anyway - maybe its easier just to get someone to upgrade their legacy SSN to the new SOSA scope and namespace and show the broader definitions are usable directly.

Rob



On Mon, 30 Jan 2017 at 10:53 Kerry Taylor <kerry.taylor@anu.edu.au<mailto:kerry.taylor@anu.edu.au>> wrote:

>Option 2: SSN new imports SOSA and “extends” classes/properties from SOSA: In this option both ontologies use a separate namespace, but SSN new extends >SOSA, meaning SSN new uses the SOSA namespace for concepts/properties that are shared between SOSA and SSN new and “extends” (narrows) them with >stronger OWL axiomatizations.

This is close, but not an accurate representation of my position. Please see the multiply-posted comments under the topic of  issue-88 , including but by no means limited to : https://lists.w3.org/Archives/Public/public-sdw-wg/2017Jan/0099.html


I will endeavour to write it up again on the wiki --- with a worked example if I can for the next  ssn meeting, although I  cannot promise to complete in time.

I would like to add that I don’t see how these things can be solved term by term  or comment-by-comment as is currently proposed by the Chair.  The architecture of modularisation has been questioned for a *very* long time  (and there are multiple unresolved issues on the tracker on this topic e.g. issue-37, issue-115, issue-120, issue-139) yet has failed to be fully articulated ---- so it seems we all  have, unsurprisingly, different interpretations of the intention. The fact that sosa , as the “core” module of ssn, was developed quite independently of ssn and with apparent disregard of these modularisation/architecture questions is rather unfortunate --- but nothing that can not  be fixed.


And, for the record, I do not accept that that any alignment between ssn or sosa is either useful or necessary.  It is frankly absurd that an ontology needs to be  ”aligned” with it’s own core! The alignment  proposed in the past week is also highly faulty – I need to put this opinion on  the record  only because I am  wary of  being told  again that “we all agreed” with something that has  simply been posted to github  by surprise.  However, because I believe it is neither useful nor necessary I will not go into details of the faults here.

--Kerry


From: Krzysztof Janowicz [mailto:janowicz@ucsb.edu<mailto:janowicz@ucsb.edu>]
Sent: Thursday, 26 January 2017 2:09 PM
To: Armin Haller <armin.haller@anu.edu.au<mailto:armin.haller@anu.edu.au>>; Simon.Cox@csiro.au<mailto:Simon.Cox@csiro.au>; phila@w3.org<mailto:phila@w3.org>; public-sdw-wg@w3.org<mailto:public-sdw-wg@w3.org>
Cc: ssimmons@opengeospatial.org<mailto:ssimmons@opengeospatial.org>; fd@w3.org<mailto:fd@w3.org>

Subject: Re: State of SSN

Hi All,


Thanks Armin for the nice summary!

Please note however that option 3 would contradict our own figures and draft as pointed out by Phil and this figure (and text) has been around for a year now.

Options 1 and 2 are what we need and as SSN imports SOSA anyway, 2 may be easier solution.

Wrt to the comments, I agree with the idea in general (and proposed it myself before) but think we need to be very, very careful here. *Abstract* comments are almost never a good idea and may actually hurt SOSA *and* SSN. Again, just to be clear about this, ideally we would have the same comment but this comment has to be on a level that is directly understandable and usable, i.e., not too abstract.

Frankly speaking, I am not so happy with having them reworked all at a time by a single person and then presented. Why don't we use the next 2-3 telco's to do this together class by class  as a group so that we do not have to re-discuss them afterwards over and over again to find a compromise. We are really running late by now :-)

Cheers and thanks again!
Jano

P.s. Let us also please switch back to a mode where everybody participates regularly and does not merely jump in a few times per year to revisit decisions taken months ago, and let us also all work in a constructive and supportive atmosphere. We have a great and impactful product and we are all interested in getting it in the best possible shape.



On 01/25/2017 03:36 PM, Armin Haller wrote:

Hi Phil,



Thanks for raising these points. I had a longer F2F conversation with Kerry yesterday to discuss her concerns around the SOSA/SSN alignment and the more general issue she raised with https://www.w3.org/2015/spatial/track/issues/139. I think I now understand her preference, which I will outline in this email. Before, I want to more clearly outline the options we have in terms of alignment between SOSA and SSN new as of Point 6 from Phil below, seeing SOSA as the core as already outlined in the first working draft.



Option 1: SSN new imports SOSA and equivalence/subclass/subproperty relations are defined in SSN: In this option both ontologies use a separate namespace and SSN new introduces its own classes/properties (in its own namespace) even for concepts/properties that are common to both ontologies, while doing so asserting equivalence and subclass/subproperty relations for those classes that are common and where appropriate.

Option 2: SSN new imports SOSA and “extends” classes/properties from SOSA: In this option both ontologies use a separate namespace, but SSN new extends SOSA, meaning SSN new uses the SOSA namespace for concepts/properties that are shared between SOSA and SSN new and “extends” (narrows) them with stronger OWL axiomatizations.

Option 3: SSN does not import SOSA and alignment between SOSA and SSN is defined in a separate file/namespace: This approach is similar to how we align SSN new to DULCE, i.e. the alignment is in a separate file with its separate namespace.



Although my personal preference from the beginning was on Option 2, my belief was that some group members are against this option, in particular, Kerry, and I was under the working assumption that at best we will achieve Option 3. In my discussion with Kerry yesterday she made it very clear that she prefers direct usage of SOSA classes/properties in SSN new. This includes the introduction of properties in SSN new that are defined in SOSA for simplicity (traversing a property path of SSN new) while adding axioms to ensure the equivalence of these simplified properties to a property path. This also means that rdfs:comments will be shared between SOSA and SSN new. Since neither of the rdfs:comments in our mapping table on the wiki (https://www.w3.org/2015/spatial/wiki/Mapping_Table) are yet particularly suited for this purpose, the proposal was:

-          To create one very abstract description for each shared concept that DOES NOT refer to classes/properties (i.e. using capital letters or camel casing), but uses English natural language. This rdfs:comment can then be supplemented by annotation properties in the two respective namespaces of SOSA and SSN new. These annotation properties can add examples, refer to classes and properties in the respective namespace using capital letters and describe the stronger semantics as required by SSN new.



If there is no objection from the group, I have volunteered to start with such an abstract description for the rdfs:comments in the mapping table. I cannot guarantee to finish by our meeting next week, but I will attempt to at least finish some of those.



Beyond that, the agreement with Kerry was that we continue (in the phone calls) with addressing the issues that have been already identified (by her) in the issue tracker in the alignment between SOSA and SSN new.



Kind regards,

Armin



On 25/1/17, 11:28 pm, "Simon.Cox@csiro.au"<mailto:Simon.Cox@csiro.au> <Simon.Cox@csiro.au><mailto:Simon.Cox@csiro.au> wrote:



    Thanks Phil -



    Just want to comment on your item 2.



    SOSA is not 'inspired by O&M' any more than it is by any of the other prior work. It was an attempt to define a core with lightweight semantics for an audience interested in describing observations, actuation or sampling. The hope was that it could also serve as a core for more semantically rich vocabularies, along the lines proposed by Jano (aka vertical and horizontal modularization). So the scope of SOSA is broad but it is axiomatically shallow - deliberately not much more than schema-org style. Certainly it picks up some ideas from O&M, in particular the notion of Samples, but it also picks up ideas from IoT (Actuators) and SSN (Platform, properties of Sensors). SOSA is definitely not something that has just come from the O&M camp.



    Simon



    -----Original Message-----

    From: Phil Archer [mailto:phila@w3.org]

    Sent: Wednesday, 25 January, 2017 20:41

    To: SDW WG Public List <public-sdw-wg@w3.org><mailto:public-sdw-wg@w3.org>

    Cc: Scott Simmons <ssimmons@opengeospatial.org><mailto:ssimmons@opengeospatial.org>; Francois Daoust <fd@w3.org><mailto:fd@w3.org>

    Subject: State of SSN



    Dear all,



    As team contact for the WG, my role is not necessarily to get involved in every aspect of each of our deliverables. As is abundantly clear from our discussions over the last couple of years, the WG members are the domain experts, not me. But, all is not well in the state of SSN and so I feel that I need to take a more active position. My mail on Monday [1] is part of that.



    My understanding of the current situation is likely to be less than 100% accurate - I know that - but what I see is:



    1. There is a lot of prior work that predates the WG: SSN, O&M, Dolce.



    2. There is SOSA, which is, I think I'm right in saying, largely inspired by the work to represent O&M in OWL and create a simple version for wider use.



    3. There is a very understandable desire to see this work become a formal standard - that's what we're chartered to do. This entails gathering evidence of usage. But the problem is that the evidence that exists is from earlier work. What's being done now might be too new and we may not be able to gather that implementation evidence. That would be a pity but it's better than a bad design driven by process. SSN has a reputation for being too complicated so let's not hesitate to simplify it.



    4. The published document states clearly that SOSA is the core and that SSN is an outer ring, with O&M and Dolce Ultra Lite alignments outside both.



    5. There is a debate about whether the alignments, especially with O&M, should be normative. In favour: O&M is a formal standard and it feels right to me that it should be but I'm open to persuasion either way.



    6. There is a debate about whether the SOSA-SSN relationship should be couched as sub classes/properties or whether one should be an extension of the other. That's a legitimate technical argument. Over to you to sort it - but as a design principle, please don't have the same property/class names in the two namespaces with different semantics (ssn:Platform and sosa:Platform, for example). My instinct is to prefer direct usage over sub classes but that's a generalist's view.



    7. There is work going on concerning the SOSA-SSN alignment that is being shared piecemeal, issue by issue. That is not right. Put it on the wiki or GH, argue about it, edit it in front of everyone. The idea of "we'll share it when it's finished" is not the way we should work.



    8. There is a lot of unhappiness in the SSN group at the moment, which is unfortunate and needs to be fixed before everyone walks away.



    9. If the group so wishes, we can easily arrange a one off long telco.



    Phil.





    [1] https://lists.w3.org/Archives/Public/public-sdw-wg/2017Jan/0096.html




    --





    Phil Archer

    Data Strategist, W3C

    http://www.w3.org/




    http://philarcher.org


    +44 (0)7887 767755<tel:+44%207887%20767755>

    @philarcher1








--

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/<http://geog.ucsb.edu/%7Ejano/>

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





--

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 Monday, 30 January 2017 14:06:21 UTC

This archive was generated by hypermail 2.4.0 : Thursday, 24 March 2022 20:31:28 UTC