Re: Subsetting data

On 2016-01-01 10:30, Phil Archer wrote:
>
>
> On 31/12/2015 10:14, Peter Baumann wrote:
>> hm, a thought: is it mandatory that a "subset extraction" has an ID?
>
> Not mandatory, but useful in some circumstances.
>
>  Subsetting
>> will always be applied to some identifiable set, so it could be considered as a
>> "modifier" of the set without own identity.
>
> Yes. I see that as a query that works today, which is different from an ID for
> a subset I want to be able to rely on indefinitely.
>
>>
>> Putting semantics into a process might make it difficult to reason about it. A
>> query (not in the URL syntax sense, but in the general sense of a declarative
>> way to express "gimme that") allows reasoning and server-side optimization.
>
> Yes, but those semantics and optimisation wouldn't be in the URI.

agreed on the optimisation part, that is the beauty of declarative languages.
On the semantics, I am not sure. A URI already _has_ model semantics in its path
section, it clearly uses a hierarchy (which is exploited, eg, in REST). Whenever
we go "into" an object this means immersing into this object's model - someone
earlier has used the term "microsyntax" for this. Whether this is embedded into
a declarative, functional, or other language, or no flexible language at all,
IMHO is a minor detail.


>
>>
>> IMHO you have raised a (the?) key question below:
>>
>>> Can you define an ontology for terms like subset, query, response that you all
>> agree on?
>>
>> - what is the set to be subset?
>> - what is a subset?
>> - what constraints have to hold on a subset?
>> - ...and after that: what are the meaningful operations that fulfil these
>> constraints?
>
> For me those questions are interesting and, *if* the DWBP and/or SDW WGs want
> to work on a document talking about this then that kind of semantics
> discussion may well be relevant. But both WGs are working at full capacity so
> we probably need to keep our ambitions modest.

understood. But sometimes there is preexisting work that might be leveraged
(this is why I brought Stephan Proell into play).

-Peter


>
> Phil
>
>
>>
>> cheers,
>> Peter
>>
>> On 2015-12-31 03:07, Rob Atkinson wrote:
>>> I'm not a strong set-theoretician - but it strikes me there are some tensions
>>> here:
>>>
>>> Does the identifier of a set mean that the members of that set are constant,
>>> known in advance and always retrievable?   Is a query endpoint a resource
>>> (does either URI or URL have meaning against a query that delivers real time
>>> data - including the use case of "at this point in time we think these things
>>> are members of this set?" )
>>>
>>> If the subset is the result of a query - and you care that it is the same
>>> subset another time you look at it - are you actually assigning an identifier
>>> to the artefact - which is the query response, whose properties include the
>>> original query, where it was made, and the time it was made?
>>>
>>> Can you define an ontology for terms like subset, query, response that you all
>>> agree on?
>>>
>>> I share Phil's implicit concern that subsetting by type with URI patterns may
>>> not be universally applicable - IMHO that equates to a "sub-register" pattern,
>>> where a set has its members defined by some identifiable process (indepent of
>>> any query functions available) - which may include explicit subsets - for
>>> example by object type, or delegated registration processes. That probably
>>> fits the UK implementation better than a query-defined subset.
>>>
>>> If subsets have some prior meaning - and a query is used to access then from a
>>> service endpint - then the query is a URL that needs to be bound to the object
>>> URI. AFAICT thats a very different thing to saying an arbitrary query result
>>> defines a subset of data.
>>>
>>> I think you may, in general, assign an ID to the artefact which is the result
>>> of a query at a given time, and if you want to make that into something with
>>> more semantics then you need make it into a new type of object which can be
>>> described in terms of what it means. I think currently the conversation is
>>> conflating these two perspectives of "subset".
>>>
>>> Cheers, and farewell to 2015.
>>> Rob Atkinson.
>>>
>>>
>>>
>>>
>>> On Thu, 31 Dec 2015 at 08:26 <Simon.Cox@csiro.au> wrote:
>>>
>>>      Another way of looking at it is that a query, encoded as a URI pattern,
>>>      defines an implicit set of potential URIs, each of which denotes a subset.
>>>
>>>      Simon J D Cox
>>>      Environmental Informatics
>>>      CSIRO Land and Water
>>>
>>>      E simon.cox@csiro.au T +61 3 9545 2365 M +61 403 302 672
>>>      Physical: Central Reception, Bayview Avenue, Clayton, Vic 3168
>>>      Deliveries: Gate 3, Normanby Road, Clayton, Vic 3168
>>>      Postal: Private Bag 10, Clayton South, Vic 3169
>>>      http://people.csiro.au/Simon-Cox
>>>      http://orcid.org/0000-0002-3884-3420
>>>      http://researchgate.net/profile/Simon_Cox3*
>>>
>>>      *
>>>     
>>> --------------------------------------------------------------------------------
>>>      *From:* Phil Archer
>>>      *Sent:* Wednesday, 30 December 2015 6:31:16 PM
>>>      *To:* Manolis Koubarakis; 'public-sdw-comments@w3.org
>>>      <mailto:public-sdw-comments@w3.org>'; Annette Greiner; Eric Stephan;
>>>      Tandy, Jeremy; public-dwbp-comments@w3.org
>>>      <mailto:public-dwbp-comments@w3.org>
>>>      *Subject:* Subsetting data
>>>
>>>      At various times in recent months I have promised to look into the topic
>>>      of persistent identifiers for subsets of data. This came up at the SDW
>>>      F2F in Sapporo but has also been raised by Annette in DWBP. In between
>>>      festive activities I've been giving this some thought and have tried to
>>>      begin to commit some ideas to a page [1].
>>>
>>>      During the CEO-LD meeting, Jeremy pointed to OpenSearch as a possible
>>>      way forward, including its geo-temporal extensions defined by the OGC.
>>>      There is also the Linked Data API as a means of doing this, and what
>>>      they both have in common is that they offer an intermediate layer that
>>>      turns a URL into a query.
>>>
>>>      How do you define a persistent identifier for a subset of a dataset? IMO
>>>      you mint a URI and say "this identifies a subset of a dataset" - and
>>>      then provide a means of programmatically going from the URI to a query
>>>      that returns the subset. As long as you can replace the intermediate
>>>      layer with another one that also returns the same subset, we're done.
>>>
>>>      The UK Government Linked Data examples tend to be along the lines of:
>>>
>>>      http://transport.data.gov.uk/id/stations
>>>      returns a list of all stations in Britain.
>>>
>>>      http://transport.data.gov.uk/id/stations/Manchester
>>>      returns a list of stations in Manchester
>>>
>>>      http://transport.data.gov.uk/id/stations/Manchester/Piccadilly
>>>      identifies Manchester Piccadilly station.
>>>
>>>      All of that data of course comes from a single dataset.
>>>
>>>      Does this work in the real worlds of meteorology and UBL/PNNL?
>>>
>>>      Phil.
>>>
>>>
>>>
>>>
>>>      [1] https://github.com/w3c/sdw/blob/gh-pages/subsetting/index.md
>>>
>>>
>>>
>>>
>>>      --
>>>
>>>
>>>      Phil Archer
>>>      W3C Data Activity Lead
>>>      http://www.w3.org/2013/data/
>>>
>>>      http://philarcher.org
>>>      +44 (0)7887 767755
>>>      @philarcher1
>>>
>>
>

-- 
Dr. Peter Baumann
 - Professor of Computer Science, Jacobs University Bremen
   www.faculty.jacobs-university.de/pbaumann
   mail: p.baumann@jacobs-university.de
   tel: +49-421-200-3178, fax: +49-421-200-493178
 - Executive Director, rasdaman GmbH Bremen (HRB 26793)
   www.rasdaman.com, mail: baumann@rasdaman.com
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Received on Friday, 1 January 2016 14:00:27 UTC