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Re: Subsetting data

From: Peter Baumann <p.baumann@jacobs-university.de>
Date: Sat, 2 Jan 2016 10:17:19 +0100
To: <Simon.Cox@csiro.au>, <phila@w3.org>, <public-sdw-comments@w3.org>, <public-dwbp-comments@w3.org>
Message-ID: <5687959F.4080505@jacobs-university.de>
looking at queries is a nicely general approach (which I like), it is just that
this transcends subsetting:
Subset = set of elements which have been preexisting (ex: vectors from a vector
bundle)
Query in addition includes
- fusion = combination of more than one object involved, such as image overlay
- aggregation = delivering scalars, something maybe not in the original object
(such as a feature bundle, which is not a scalar) -> type change
- any other type of processing (such as rasterizing vectors, or vectorizing
rasters) -> type change

Note that this narrow definition of subset includes an OGC WFS / Filter Encoding
right away, whereas the "extended view" does not.

-Peter


On 2016-01-02 01:10, Simon.Cox@csiro.au wrote:
> > to be persistent, identifiers should not include queries against a specific
> API or query endpoint. 
>
> For sure. I didn't say anything about the form of the query. It may not even
> look like a query. Opensearch is an obvious model for
> implementation-independent syntax (after all it's just key-value pairs).
>
> However, I do think it is worth keeping the notion of subset=query result in
> view. Sure, some query results may be more persistent and therefore worthy of
> denotation with a special identifier. But the same subset will also be the
> result of some query anyway. That's just an example of non-unique identifiers.
>
> Simon J D Cox
>
> Research Scientist
>
> Environmental Information Infrastructures
>
> Land and Water
>
> CSIRO
>
>  
>
> E simon.cox@csiro.au T +61 3 9545 2365 M +61 403 302 672
>
>    Physical: Reception Central, Bayview Avenue, Clayton, Vic 3168
>
>    Deliveries: Gate 3, Normanby Road, Clayton, Vic 3168
>
>    Postal: Private Bag 10, Clayton South, Vic 3169
>
> people.csiro.au/Simon-Cox
>
> orcid.org/0000-0002-3884-3420
>
> researchgate.net/profile/Simon_Cox3
>
>  
>
> *
>  
> *
> --------------------------------------------------------------------------------
> *From:* Phil Archer
> *Sent:* Friday, 1 January 2016 9:05:25 AM
> *To:* Cox, Simon (L&W, Clayton); public-sdw-comments@w3.org;
> public-dwbp-comments@w3.org
> *Subject:* Re: Subsetting data
>
>
>
> On 30/12/2015 21:26, 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.
>
> True, but to be persistent, identifiers should not include queries
> against a specific API or query endpoint. That, for me, is the key
> point. OpenSearch provides a model where a query is included in a URL
> that can be considered persistent because there is a layer of
> indirection that could be changed without the URL changing, but a URL
> that includes a SQL or SPARQL query directly must be considered
> ephemeral IMO.
>
> Phil
>
>
> >
> > 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'; Annette Greiner; Eric
> Stephan; Tandy, Jeremy; 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
> >
> >
>
> -- 
>
>
> 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
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Received on Saturday, 2 January 2016 09:17:56 UTC

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