Re: [linking-data] What should I link to? (or link between)

Great Points Jon,

IMHO ..

1) No this is a key point, WxS are poor web citizens not exposing their
content whatsoever in a linked data way.

2) Agree, or we recognise a collection of elements from a dataset (the
results of a query ?) as a "new" thing with it's own URL ?

Ed


On Wed, 30 Sep 2015 at 09:31 Jon Blower <j.d.blower@reading.ac.uk> wrote:

> Sorry! My mistake, I managed to confuse myself (easily done). Yes, the URI
> doesn’t have to be opaque from the server’s point of view, but I meant that
> the client shouldn’t try to decompose the URL. This means that the client
> doesn’t necessarily know ahead of time that a URL represents a WCS (or
> whatever) query.
>
> The questions in my mind are:
>
> 1. Is a WxS, OPeNDAP or other Web Service URL a good Linked Data
> identifier? I’m not really convinced it is, but I’d need to unpick things
> further.
>
> 2. If I want to annotate an arbitrary subset of a dataset, it may not even
> be possible to specify this subset in a single URL, depending on the
> protocol(s) the server offers. So I think we might still need a mechanism
> to *describe* subsets independent of protocol.
>
> Cheers,
> Jon
>
>
>
>
>
>
> On 30 Sep 2015, at 05:35, Simon.Cox@csiro.au wrote:
>
> Ø  Given that URIs are supposed to be opaque …
>
>
>
> Not exactly. URIs are not required to be transparent, and from the
> client’s point of view they should be treated as opaque. But there may be a
> good reason from the server-side point of view for them to encode a query –
> just think of it as a formula for minting a unique URI to denote a subset.
> And (all other things being equal) there is no harm done if a URI is
> predictable, and many of them on the web are!
>
>
>
> Furthermore, I find it hard to imagine an opaque URI if it denotes a
> *query*, which is more-or-less essential if it is a regular subset.
>
>
>
> Simon
>
>
>
> *From:* Jon Blower [mailto:j.d.blower@reading.ac.uk
> <j.d.blower@reading.ac.uk>]
> *Sent:* Tuesday, 29 September 2015 6:02 PM
> *To:* Peter Baumann <p.baumann@jacobs-university.de>
> *Cc:* Cox, Simon (L&W, Clayton) <Simon.Cox@csiro.au>; Jeremy Tandy <
> jeremy.tandy@gmail.com>; public-sdw-wg@w3.org
> *Subject:* Re: [linking-data] What should I link to? (or link between)
>
>
>
> Hi Peter,
>
>
>
> Yes, of course, WCS can *access* subsets of a coverage (so can other
> protocols like OPeNDAP) but I think we need a protocol-independent way to
> *identify* the subsets.
>
>
>
> I’m picturing an RDF fragment that encodes things like the band/variable,
> spatiotemporal (or index) coordinates, and anything else. Given that URIs
> are supposed to be opaque (i.e. we’re not supposed to encode semantics in
> the URL), I think we have to define URIs that point to subset definitions.
>
>
>
> Clearly any mechanism needs to be compatible with the data models of WCS
> (and CIS), but I don’t think we should just adopt the WCS GetCoverage URL
> as the identifier for subsets.
>
>
>
> Cheers,
>
> Jon
>
>
>
> On 29 Sep 2015, at 09:32, Peter Baumann <p.baumann@jacobs-university.de>
> wrote:
>
>
>
> that's what we typically do with a GetCoverage request as a URL, it allows
> for trimming and slicing a coverage (down to single pixels). Beyond that,
> you can link to single bands, representations of the coverage in other
> CRSs, scaled versions, etc. And it's standard by OGC and soon INSPIRE and
> ISO.
> -Peter
>
> On 2015-09-29 03:04, Simon.Cox@csiro.au wrote:
>
> Ø  probably don’t want to link between individual pixels in a satellite
> image?
>
>
>
> Not always, but sometimes. It always seemed to me that a key requirement
> for joining gridded data and linked data was to have a URI for a subsets,
> perhaps even down to a single pixel. Does QB help here?
>
>
>
> Simon
>
>
>
> *From:* Jon Blower [mailto:j.d.blower@reading.ac.uk
> <j.d.blower@reading.ac.uk>]
> *Sent:* Tuesday, 29 September 2015 7:13 AM
> *To:* Jeremy Tandy <jeremy.tandy@gmail.com> <jeremy.tandy@gmail.com>
> *Cc:* SDW WG Public List <public-sdw-wg@w3.org> <public-sdw-wg@w3.org>
> *Subject:* Re: [linking-data] What should I link to? (or link between)
>
>
>
> Is this a question about granularity? E.g. we definitely want to link
> between datasets, but probably don’t want to link between individual pixels
> in a satellite image?
>
>
>
> One use case we are seeing in MELODIES a lot is that we want to link to
> *features* that we extract from images, but probably not the raster data
> itself.
>
>
>
> Cheers,
>
> Jon
>
>
>
>
>
> On 24 Sep 2015, at 09:30, Jeremy Tandy <jeremy.tandy@gmail.com> wrote:
>
>
>
> Email thread for collecting discussion on the question: "What should I
> link to? (or between)"
>
>
>
> The related wiki entry for this questions is here [1]
>
>
>
> For instructions about how to engage with this discussion, please see my
> previous email [2].
>
>
>
> Many thanks. Jeremy
>
>
>
> [1]:
> https://www.w3.org/2015/spatial/wiki/Linking_Data#What_should_I_link_to.3F_.28or_link_between.29
>
> [2]: https://lists.w3.org/Archives/Public/public-sdw-wg/2015Sep/0044.html
>
>
>
>
>
>
>
> --
>
> 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
>
>    tel: 0800-rasdaman, fax: 0800-rasdafax, mobile: +49-173-5837882
>
> "Si forte in alienas manus oberraverit hec peregrina epistola incertis ventis dimissa, sed Deo commendata, precamur ut ei reddatur cui soli destinata, nec preripiat quisquam non sibi parata." (mail disclaimer, AD 1083)
>
>
>
>
>
>
>
>
> --

*Ed Parsons*
Geospatial Technologist, Google

Google Voice +44 (0)20 7881 4501
www.edparsons.com @edparsons