Re: Wanted: feedback on UCR requirements

Hello Linda, Matt,

Thanks to the BP editors for taking time to look at these issues. The
solution to issue 28 looks sensible to me, but I would like to ask Matt if
he agrees with the change. The requirement for a default/canonical CRS
comes directly from the use case Combining spatial RDF data for integrated
querying in a triplestore
<http://w3c.github.io/sdw/UseCases/SDWUseCasesAndRequirements.html#CombiningSpatialRDFDataForIntegratedQueryingInATriplestore>,
which Matt contributed. It seems to me that if the requirement in its new
wording is met, the problem of having to do coordinate transformations (for
instance in federated SPARQL queries) still exists. So I wonder if the new
wording does justice to the use case.

I think the problem of having to perform coordinate transformation when
combining datasets could also be solved by recommending using multiple CRSs
in data publications. A procedure for combining data from two data sets
would then have a higher chance of finding a CRS that both data sets have
in common. Having good standards for making the CRS known of course would
help a lot in that process, and the requirement in its new wording would
help there.

Another way of mitigating the problem of having to transform coordinates
would be to have a more general lat-lon CRS than the likes of ETRS89 and
WGS84, which could not be used for high precision data but could aid
interoperabilty.

So if we acknowledge that there could be different solutions for the
problem of having to perform coordinate transformation when combining data,
would that mean there is room for a new requirement that specifies the
problem and does not hint at possible solutions? For example
"Recommendations or standards are needed to avoid having to transform
coordinates when data from different sources are combined"?

Regards,
Frans

On 12 July 2016 at 16:17, Linda van den Brink <l.vandenbrink@geonovum.nl>
wrote:

> Hi Frans,
>
>
>
> We (the BP editors) have discussed the BP issues and concluded:
>
> -          issue 23: We think this issue can be closed because in our
> view the wording as it currently is for this requirement in the UCR is
> fine. We will try to address the questions that are raised in the issue in
> the BP. I created an issue in Github so we don’t forget.
> https://github.com/w3c/sdw/issues/298
>
> -          issue 28: The requirement according to us three is: “that
> clients or users must always be able to determine what CRS is used.” This
> could be because it’s present in the data in some form, or because it’s
> determined by the spec (and this could be that if unspecified in the data,
> there’s some default).  In the BP we will go into the question of when a
> more precise CRS than WGS84 is needed. We hope this helps us resolve the
> issue.
>
>
>
> Linda
>
>
>
> *Van:* Frans Knibbe [mailto:frans.knibbe@geodan.nl]
> *Verzonden:* woensdag 6 juli 2016 15:01
> *Aan:* Jeremy Tandy; Linda van den Brink; Payam Barnaghi; Simon Cox;
> Chris Little; Krzysztof Janowicz; Armin Haller; danh.lephuoc@deri.org;
> Bill Roberts; Kerry Taylor
> *CC:* SDW WG Public List
> *Onderwerp:* Re: Wanted: feedback on UCR requirements
>
>
>
> Dear editors,
>
>
>
> I haven't had much response to my question so far. So as an aid, here is a
> list of the open issues marked in the current UCR draft:
>
>
> <https://www.w3.org/2015/spatial/track/issues/20>
>
> ISSUE-20 <https://www.w3.org/2015/spatial/track/issues/20> (SSN)
>
> ISSUE-23 <https://www.w3.org/2015/spatial/track/issues/23> (Best
> Practices)
>
> ISSUE-24 <https://www.w3.org/2015/spatial/track/issues/24> (SSN)
>
> ISSUE-26 <https://www.w3.org/2015/spatial/track/issues/26> (Time)
>
> ISSUE-28 <https://www.w3.org/2015/spatial/track/issues/28> (Best
> Practices)
>
>
>
> Wouldn't it be nice if we can resolve these issues before the next and
> final PWD of the UCR document this month?
>
>
>
> Regards,
>
> Frans
>
>
>
>
>
>
>
> 2016-06-22 13:12 GMT+02:00 Frans Knibbe <frans.knibbe@geodan.nl>:
>
> Dear editors of the BP/Time/SSN/Coverage deliverable,
>
>
>
> In preparation of a next public working draft of the UCR document I would
> like to ask you for feedback on the requirements for your deliverable as
> specified in the UCR document. Section 6
> <http://w3c.github.io/sdw/UseCases/SDWUseCasesAndRequirements.html#RequirementsByDeliverable>
> list requirements grouped by deliverable. By now you will have stared long
> & hard at those requirements, and perhaps you concluded that some or not
> clear yet, or that something else is wrong. Perhaps requirements or even
> important use cases are missing?
>
>
>
> While we are working on a new batch of publications before TPAC, it would
> be nice if the requirements in the UCR document are (among) the ones you
> are actually working with. I think the public we are writing for deserves
> that coherence. I presume your deliverables will link back to the UCR
> document and explain how requirements are met or why requirements are not
> met. So if you think any changes are required in the UCR document resulting
> from your work on your deliverable, please inform me.
>
>
>
> Thanks,
>
> Frans
>
>
>