- From: Peter Baumann <p.baumann@jacobs-university.de>
- Date: Tue, 5 Jan 2016 22:43:34 +0100
- To: Rob Atkinson <rob@metalinkage.com.au>, <janowicz@ucsb.edu>, Dan Brickley <danbri@google.com>, Clemens Portele <portele@interactive-instruments.de>
- CC: Phil Archer <phila@w3.org>, Simon Cox <Simon.Cox@csiro.au>, <amgreiner@lbl.gov>, <ericphb@gmail.com>, <jeremy.tandy@metoffice.gov.uk>, <koubarak@di.uoa.gr>, <public-dwbp-comments@w3.org>, <public-sdw-comments@w3.org>
- Message-ID: <568C3906.9090205@jacobs-university.de>
+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)
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Received on Tuesday, 5 January 2016 21:44:20 UTC