Re: Subsetting data

+1
-Peter

On 2016-01-05 22:18, Rob Atkinson wrote:
>
> given stable URIs for subsets (which I don think there is any disagreement
> about) AFACIT there are two unresolved issues - both concerned with the scope
> of the BP:
> 1) What is the BP for describing how subsets relate to each other and the
> master data set (avoiding implementation details)
> 2) what is the relationship between identifiable subsets, query endpoints and
> the subsets returned - do they all have identifiers, and what is the BP for a
> common vocabulary to relate these different aspects
>
> Maybe a valid result is to say that there really isnt a BP in term of these
> requirements - and stop at saying URI idenfiers for subsets is a Good Thing
>  Nobody Knows How To Use and throw out a challenge
>
> Rob
>
>
> On Wed, 6 Jan 2016 at 05:13 Krzysztof Janowicz <janowicz@ucsb.edu
> <mailto:janowicz@ucsb.edu>> wrote:
>
>     Hi Dan,
>
>
>>     Isn't a "subset" just a query result, or which there are effectively an
>>     unlimited number?
>
>     I would say so.
>
>
>>     Storing a query so it can be re-run against evolving data has value.
>>     Having a URI for that, perhaps less so.
>
>     There are many cases, particularly if dealing with streams of data, e.g.,
>     form sensors, where having URIs for subsets is very useful, and, in fact,
>     there are many ways to do so. Some years ago we implemented one such
>     solution at 52North where we developed a transparent (i.e., invisible)
>     proxy on top of an endpoint that translates a URI minted in a specific way
>     to return specific query results.  For instance, the URI
>     http://my.authority.org/observations/samplingtimes/ont:time:relation:between,2008-01-10T14:00,2008-01-12T16:00/sensors/thermometer1/observedproperties/temperature
>     points to the observation collection with all temperature observations
>     from January 10th 2008 at 2pm until January 12th at 4pm made by
>     thermometer1. Having such URIs (and proxies) is one way of mitigating the
>     problem that the content  referenced by URIs should be as stable as
>     possible which is (often) not the case for sensor data. In our case we
>     worked on transparently mapping between SPARQL and OGC's Sensor
>     Observation Services but the idea can (and has been) used in many other
>     settings.
>
>     Happy new year.
>     Krzysztof
>
>
>     On 12/31/2015 03:09 AM, Dan Brickley wrote:
>>
>>     Isn't a "subset" just a query result, or which there are effectively an
>>     unlimited number?
>>
>>     Storing a query so it can be re-run against evolving data has value.
>>     Having a URI for that, perhaps less so.
>>
>>     Dan
>>
>>     On Thu, 31 Dec 2015, 08:14 Clemens Portele
>>     <portele@interactive-instruments.de
>>     <mailto:portele@interactive-instruments.de>> wrote:
>>
>>         Rob, 
>>
>>         what you describe seems to apply to the dataset (resource) the same
>>         way it would apply to any subset resource. I.e. are you discussing a
>>         more general question, not the subsetting question?
>>
>>         Phil,
>>
>>         a (probably often unproblematic) restriction to the
>>         temperature/uk/london or stations/manchester approach is that there
>>         is only one path, so you end up with limitations on the subsets. If
>>         you want to support multiple subsets, e.g. also stations where high
>>         speed trains stop, stations that have a ticket shop, etc. then there
>>         are several issues with a /{dataset}/{subset}/…/{subset}/{object}
>>         approach. These include an unclear URI scheme ("manchester" and
>>         "eurostar" would be on the same path level), potential name
>>         collisions of subset names of different subsetting categories, and
>>         multiple URIs for the same feature/object.
>>
>>         Best regards,
>>         Clemens
>>
>>
>>>         On 31 Dec 2015, at 03:07, Rob Atkinson <rob@metalinkage.com.au
>>>         <mailto:rob@metalinkage.com.au>> 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
>>>         <mailto: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 <mailto: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 <http://philarcher.org/>
>>>             +44 (0)7887 767755
>>>             @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
>

-- 
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 Tuesday, 5 January 2016 21:44:20 UTC