- From: Frans Knibbe <frans.knibbe@geodan.nl>
- Date: Fri, 9 Sep 2016 14:41:18 +0200
- To: "public-sdw-wg@w3.org" <public-sdw-wg@w3.org>
- Message-ID: <CAFVDz42VvPY4FJJndoyTKAHQJ-NJBkeRFmdq0RTG+dban3R0xA@mail.gmail.com>
First, I would like to note that this issue is now an ISSUE. It is UCR ISSUE-74 <https://www.w3.org/2015/spatial/track/issues/74>, to be precise. I hope this message sufficiently links this thread to the issue. The issue states that UoM and accuracy should be covered in the UCR and BP documents, and be respected in other deliverables too. Can we start with properly addressing the topics in the UCR document? Hopefully that gives some direction to the way best practices should be set up too. I would like to repeat proposals made in the first message of this thread: 1) We expand CRS definition <http://w3c.github.io/sdw/UseCases/SDWUseCasesAndRequirements.html#CRSDefinition> requirement a bit to make it clear that a CRS definition should include an indication of UoM. For instance: "There should be a recommended way of referencing a Coordinate Reference System (CRS) with a HTTP URI, and to get useful data about the CRS when that URI is dereferenced. The CRS data should include the unit of measurement of the CRS." 2) We add a new requirement: "The use of precision that matches uncertainty in coordinate data should be facilitated and encouraged" Would those things suffice as far as the UC&R go? Regards, Frans On 6 September 2016 at 08:08, Jeremy Tandy <jeremy.tandy@gmail.com> wrote: > Hi. We already do provide a link with in the BP doc to this ... See : > http://w3c.github.io/sdw/bp/#desc-accuracy > > That said, it's buried there too. Seems that UoM (and other > record/property level metadata) is deserving of its own BP? > > Jeremy > > > > On Tue, 6 Sep 2016 at 00:33, Byron Cochrane <bcochrane@linz.govt.nz> > wrote: > >> That was buried! I think it would be useful to provide a link in SDWBP to >> this (https://www.w3.org/TR/vocab-dqv/#ExpressDatasetAccuracyPrecision) >> if we hope for others to find this guidance. >> >> Cheers, >> Byron >> >> -----Original Message----- >> From: Simon.Cox@csiro.au [mailto:Simon.Cox@csiro.au] >> Sent: Tuesday, 6 September 2016 11:14 a.m. >> To: andrea.perego@jrc.ec.europa.eu; frans.knibbe@geodan.nl; >> jeremy.tandy@gmail.com >> Cc: rob@metalinkage.com.au; jlieberman@tumblingwalls.com; >> chris.little@metoffice.gov.uk; public-sdw-wg@w3.org >> Subject: RE: Requirements for units of measure, accuracy and precision >> >> Thanks Andrea - >> >> But gosh - you have to dig deep to find it. And the sub-head 'dataset >> precision and accuracy' does not exactly shout 'units of measure' or >> 'scale' does it? It looks like a side-effect rather than a central concern. >> >> Am frankly amazed that this issue is not more central for quantitative >> data, which is a significant subset of general 'data on the web'. >> >> Simon >> >> -----Original Message----- >> From: Andrea Perego [mailto:andrea.perego@jrc.ec.europa.eu] >> Sent: Monday, 5 September 2016 7:15 PM >> To: Frans Knibbe <frans.knibbe@geodan.nl>; Jeremy Tandy < >> jeremy.tandy@gmail.com> >> Cc: Rob Atkinson <rob@metalinkage.com.au>; Joshua Lieberman < >> jlieberman@tumblingwalls.com>; Chris Little < >> chris.little@metoffice.gov.uk>; Cox, Simon (L&W, Clayton) >> <Simon.Cox@csiro.au>; public-sdw-wg@w3.org >> Subject: Re: Requirements for units of measure, accuracy and precision >> >> Just to note that UoMs are included in some of the examples of DQV, in >> particular in relation to spatial resolution - see: >> >> https://www.w3.org/TR/vocab-dqv/#ExpressDatasetAccuracyPrecision >> >> For more details, see my earlier messages on this topics [1,2]. >> >> Please note that the examples above are some of those added by the DWBP >> WG following our comments on the "representation of precision and accuracy" >> - see thread starting here: >> >> https://lists.w3.org/Archives/Public/public-sdw-comments/ >> 2016Mar/0001.html >> >> and related DWBP issue: >> >> https://www.w3.org/2013/dwbp/track/issues/243 >> >> >> Since DWBP deliverables include UoMs only for spatial resolution, I think >> it's up to us to address the other relevant use cases - possibly by >> building upon the DQV approach, if appropriate. >> >> Andrea >> >> ---- >> [1]https://lists.w3.org/Archives/Public/public-sdw-wg/2016Jul/0164.html >> [2]https://lists.w3.org/Archives/Public/public-sdw-wg/2016Jul/0253.html >> >> >> On 02/09/2016 17:26, Frans Knibbe wrote: >> > All, >> > thanks for replying, and a special thanks to Rob for fencing off >> > Jeremy's hijack attempt :-) >> > >> > An attempt to summarize and suggest steps to be taken: >> > >> > * One of us could submit a comment to the DWBPWG that we feel >> > indication of UoM and uncertainty in quantitative data deserves >> > attention in their document. Is there a volunteer? >> > (I would like to note that an earlier DWBP comment had me suggesting >> > they should encourage data providers using significant digits, which >> > can be seen a good way to meet the requirement for indicating >> > uncertainty in quantitative data. After some discussion, the DWBP >> > decided the subject was out of scope for data on the web (see this >> > message >> > <https://lists.w3.org/Archives/Public/public-dwbp- >> comments/2016Jun/0012.html>), >> > because it applies to the broader domain of quantitative data (that >> > can exist outside of the Web too). So I think next to the DWBP >> > already being fixed there is little chance of the comment being >> > acted upon.) >> > * There seems to be agreement that the UoM thing should be tied to CRS >> > definitions. Can we solve the issue by listing an indication of UoM >> > as one of the types of 'useful information' about a CRS in the CRS >> > Definition requirement >> > <http://w3c.github.io/sdw/UseCases/SDWUseCasesAndRequirements. >> html#CRSDefinition>? >> > Of course I would need to list some other typical properties of CRSs >> > for good measure, but that should not be a problem. >> > * We add a BP requirement to the UC&R that says "The use of precision >> > that matches uncertainty in coordinate data should be facilitated >> > and encouraged". Note that we already havea requirement for >> > describing spatial resolution in the metadata >> > <http://w3c.github.io/sdw/UseCases/SDWUseCasesAndRequirements. >> html#SpatialMetadata>. >> > >> > I hope we can agree on making concrete changes to the UCR document (or >> > not) soon. >> > >> > Greetings, >> > Frans >> > >> > >> > On 1 September 2016 at 13:41, Jeremy Tandy <jeremy.tandy@gmail.com >> > <mailto:jeremy.tandy@gmail.com>> wrote: >> > >> > @ Rob: >> > >> > > I think we need to step back and decide if this is about >> > requirements or BP >> > >> > Good point. I'll take the best practice question to a separate >> > thread ... >> > >> > On Wed, 31 Aug 2016 at 23:44 Rob Atkinson <rob@metalinkage.com.au >> > <mailto:rob@metalinkage.com.au>> wrote: >> > >> > >> > I think we need to step back and decide if this is about >> > requirements or BP, and target the elements of conversation >> > better to which deliverable is affected. >> > >> > IMHO there is a _requirement_ for a canonical mechanism to state >> > aspects of spatial properties. >> > I also think its a requirement for that mechanism to be common >> > with broader requirements for publishing metadata. Its not a >> > uniquely spatial concern - but spatial is typified by this being >> > relevant at dataset, service, feature and property levels of >> > granularity and the need for users to be able to discover and >> > interpret this information regardless of where it is best >> placed. >> > >> > If there is no consensus on an identifiable Best Practice - IMHO >> > we should note this as an unmet requirement in the BP document , >> > and refer to the catch-all (reuse something!) BP >> > >> > Rob >> > >> > >> > >> > >> > On Thu, 1 Sep 2016 at 02:27 Joshua Lieberman >> > <jlieberman@tumblingwalls.com >> > <mailto:jlieberman@tumblingwalls.com>> wrote: >> > >> > Jeremy, >> > >> > These may not be the terms we want to make a best practice >> > of. Precision (closeness of repeated measurements) and >> > accuracy (closeness to truth) are really concepts that are >> > impossible to compute directly, since one can’t either make >> > all possible repeated measurements, nor actually make true >> > measurements. What one can estimate and report is >> > uncertainty (the range within which the true value has some >> > likelihood of occurring if we accounted for all sources of >> > error) and resolution (predicted precision or fineness of >> > measurement). >> > >> > The spatial question in this is whether one should report >> > multidimensional uncertainty and resolution, using such >> > things as error ellipses or fuzzy geometric boundaries. It >> > could be a real mess to make a map with fuzzy topographic >> > contours, but the variation in hypsometric uncertainty >> > between different published maps would probably shock people >> > if they were made aware of it. >> > >> > Josh >> > >> >> On Aug 31, 2016, at 11:13 AM, Jeremy Tandy >> >> <jeremy.tandy@gmail.com <mailto:jeremy.tandy@gmail.com>> >> >> wrote: >> >> >> >> Ignoring the UoM thing for now (although I can see @josh's >> >> point about it being needed to define CRS), can folks tell >> >> me whether BP 5 "Describe the positional accuracy of >> >> spatial data" [1] is on the right track to meet >> >> requirements about precision and accuracy? If not, please >> >> can one of you fine folks make some suggests content >> changes? >> >> >> >> Thanks in advance. Jeremy >> >> >> >> [1]: http://w3c.github.io/sdw/bp/#desc-accuracy >> >> <http://w3c.github.io/sdw/bp/#desc-accuracy> >> >> >> >> On Wed, 31 Aug 2016 at 12:32 Joshua Lieberman >> >> <jlieberman@tumblingwalls.com >> >> <mailto:jlieberman@tumblingwalls.com>> wrote: >> >> >> >> Given that there are specific spatial aspects to both >> >> precision and uom, for example a precision ellipsoid >> >> is a geometry and a unit of measure such as an >> >> altitude is relatively to a datum such as a geoid, it >> >> seems reasonable to me that these can be included SDW >> >> BP's without worrying overmuch whether DWBP will ever >> >> get to these sorts of multi-dimensional and affine >> >> space issues. >> >> >> >> Josh >> >> >> >> Joshua Lieberman, Ph.D. >> >> Principal, Tumbling Walls Consultancy >> >> Tel/Direct: +1 617-431-6431 <tel:%2B1%20617-431-6431> >> >> jlieberman@tumblingwalls.com >> >> <mailto:jlieberman@tumblingwalls.com> >> >> >> >> On Aug 31, 2016, at 07:19, Little, Chris >> >> <chris.little@metoffice.gov.uk >> >> <mailto:chris.little@metoffice.gov.uk>> wrote: >> >> >> >>> Simon, Rob,____ >> >>> >> >>> __ __ >> >>> >> >>> I support submitting a formal public comment to DWBP, >> >>> AND doing something specific to spatial.____ >> >>> >> >>> __ __ >> >>> >> >>> Chris____ >> >>> >> >>> __ __ >> >>> >> >>> *From:*Rob Atkinson [mailto:rob@metalinkage.com.au] >> >>> *Sent:* Friday, August 26, 2016 1:42 AM >> >>> *To:* Simon.Cox@csiro.au <mailto:Simon.Cox@csiro.au>; >> >>> frans.knibbe@geodan.nl >> >>> <mailto:frans.knibbe@geodan.nl>; public-sdw-wg@w3.org >> >>> <mailto:public-sdw-wg@w3.org> >> >>> *Subject:* Re: Requirements for units of measure, >> >>> accuracy and precision____ >> >>> >> >>> __ __ >> >>> >> >>> When this was raised and we asked Phil for guidance, >> >>> we were basically told DWBP is pretty much fixed, if >> >>> we care it behooves us to address it even ifs its a >> >>> more general issue. I think we just need to note its >> >>> a more general issue, and provide what we feel is a >> >>> BP otherwise there is really no useful path to >> >>> implementation.____ >> >>> >> >>> __ __ >> >>> >> >>> Given precision is a first class concern of spatial >> >>> data - as spatial resolution is going to be ever >> >>> critical in the Internet of Things especially, we >> >>> need to handle this. Precision may be common to a >> >>> dataset due to a common methodology, specific to a >> >>> sensor, or time-varying - such as GPS coordinates. >> >>> The BP needs to address how to attach this at this >> >>> different levels of granularity. We need to cover >> >>> both measured position and gridded coverages as well, >> >>> and preferably not with completely different >> >>> approaches. Precision is not generally an attribute >> >>> of a CRS, unless we are going to define CRS for every >> >>> possible grid - and that would be a fairly major >> >>> departure from existing practice i suspect.____ >> >>> >> >>> __ __ >> >>> >> >>> UoM is a _similar_ case, and not inherently spatial, >> >>> so i agree it can be localised to CRS , TRS, but I >> >>> see no harm in tying it in to the same pattern as >> >>> spatial precision - whats needed is a BP to provide >> >>> metadata about values, to meet the hard requirement >> >>> of spatial CRS and precision, but its useful to >> >>> suggest this would be applicable to UoM. Certainly >> >>> having a completely different set of patterns for >> >>> attribution of uom and CRS feels like sub-optimal >> >>> practice. ____ >> >>> >> >>> __ __ >> >>> >> >>> Rob____ >> >>> >> >>> __ __ >> >>> >> >>> __ __ >> >>> >> >>> On Fri, 26 Aug 2016 at 10:09 <Simon.Cox@csiro.au >> >>> <mailto:Simon.Cox@csiro.au>> wrote:____ >> >>> >> >>> Ø The lack of information on units of measure >> >>> and the apparent lack of concern for proper >> >>> indication of uncertainty in numbers are >> >>> widespread in spatial data and something should >> >>> definitely be done about that. However, I >> >>> maintain that both problems are more general than >> >>> spatial data and are therefore out of scope for >> >>> the UCR document. We have tried hard to limit the >> >>> UCR requirements to only spatial data on the >> >>> web.____ >> >>> >> >>> ____ >> >>> >> >>> Frans – I agree with this assessment in >> >>> principle. Should we try to pass it back up to >> >>> the DWBP group? ____ >> >>> >> >>> ____ >> >>> >> >>> Best Practice 7 >> >>> https://www.w3.org/TR/dwbp/#quality >> >>> <https://www.w3.org/TR/dwbp/#quality> refers off >> >>> to the Data Quality Vocabulary, which may mean >> >>> they think it is dealt with, but I’m not >> >>> convinced. It’s one more step away from the >> >>> readers, at least, and none of the examples show >> >>> units of measure, or suggest where they would be >> >>> found. ‘units’ or ‘uom’ does not appear in their >> >>> document (in the sense that we mean, anyway). >> >>> ____ >> >>> >> >>> ____ >> >>> >> >>> However, this document is still in ‘Working >> >>> Draft’ status, although it is certainly a pretty >> >>> mature document by now. We could start by making >> >>> a comment on their public list >> >>> https://lists.w3.org/Archives/Public/public-dwbp- >> comments/ >> >>> <https://lists.w3.org/ >> Archives/Public/public-dwbp-comments/> >> >>> to the effect that ____ >> >>> >> >>> ____ >> >>> >> >>> ‘The requirement to know the units of measure for >> >>> quantitative data (or another kind of ‘reference >> >>> system’ for other kinds of data values) is not >> >>> mentioned in https://www.w3.org/TR/dwbp/. Units >> >>> are required in order to use quantitative data, >> >>> so the Data on the Web Best Practices should >> >>> include a recommendation on the topic. This >> >>> affects the following benefit categories: >> >>> Comprehension (C), Processability (P), Reuse (R)’ >> >>> ____ >> >>> >> >>> ____ >> >>> >> >>> But perhaps this is a place where some more >> >>> formal coordination between the groups is >> >>> warranted? ____ >> >>> >> >>> @phila – has this issue ever been discussed in >> >>> the DWBP group? A quick search of the email >> >>> archive doesn’t turn anything up. ____ >> >>> >> >>> ____ >> >>> >> >>> --____ >> >>> >> >>> As a side comment – it is kinda remarkable how >> >>> this gets overlooked. I raised it in the Open >> >>> Knowledge forum on their Data >> >>> Packaging/Frictionless Data initiative. As soon >> >>> as I mentioned it there was acceptance that it is >> >>> in scope, but somehow no-one had brought it up >> >>> until then. ____ >> >>> >> >>> ____ >> >>> >> >>> Simon ____ >> >>> >> >>> ____ >> >>> >> >>> *From:*Frans Knibbe >> >>> [mailto:frans.knibbe@geodan.nl >> >>> <mailto:frans.knibbe@geodan.nl>] >> >>> *Sent:* Thursday, 25 August 2016 10:50 PM >> >>> *To:* SDW WG Public List <public-sdw-wg@w3.org >> >>> <mailto:public-sdw-wg@w3.org>>____ >> >>> >> >>> >> >>> *Subject:* Requirements for units of measure, >> >>> accuracy and precision____ >> >>> >> >>> ____ >> >>> >> >>> Hello,____ >> >>> >> >>> ____ >> >>> >> >>> In messages >> >>> https://lists.w3.org/ >> Archives/Public/public-sdw-wg/2016Aug/0172.html >> >>> <https://lists.w3.org/ >> Archives/Public/public-sdw-wg/2016Aug/0172.html> >> >>> and ____ >> >>> >> >>> https://lists.w3.org/ >> Archives/Public/public-sdw-wg/2016Aug/0109.html >> >>> <https://lists.w3.org/ >> Archives/Public/public-sdw-wg/2016Aug/0109.html> >> >>> the possibility of adding new requirements to the >> >>> UC&R doc was brought forward. Those should be >> >>> requirements that____ >> >>> >> >>> ____ >> >>> >> >>> A) the units of measure (UoM) in spatial data >> >>> should be made clear____ >> >>> >> >>> B) the precision of spatial data should be made >> >>> clear____ >> >>> >> >>> ____ >> >>> >> >>> From the looks of it, those requirements would at >> >>> least be requirements for the BP >> >>> deliverable.____ >> >>> >> >>> ____ >> >>> >> >>> The topic was also discussed in the last SSN >> >>> teleconference >> >>> <https://www.w3.org/2016/08/23-sdwssn-minutes>. I >> >>> thought it would be good to create a separate >> >>> thread for these related issues.____ >> >>> >> >>> ____ >> >>> >> >>> I will first repeat my initial response: The >> >>> requirements are very good requirements. The lack >> >>> of information on units of measure and the >> >>> apparent lack of concern for proper indication of >> >>> uncertainty in numbers are widespread in spatial >> >>> data and something should definitely be done >> >>> about that. However, I maintain that both >> >>> problems are more general than spatial data and >> >>> are therefore out of scope for the UCR document. >> >>> We have tried hard to limit the UCR requirements >> >>> to only spatial data on the web. This constraint >> >>> is specifically mentioned in the section on >> >>> methodology >> >>> <http://w3c.github.io/sdw/UseCases/ >> SDWUseCasesAndRequirements.html#Methodology>. >> >>> If we were to neglect this constraint, then the >> >>> amount of requirements could run out of hand >> >>> quickly, the decisions on which requirements to >> >>> include or not would become very arbitrary and >> >>> the deliverable teams that are tasked with >> >>> meeting requirements would inevitably find out >> >>> that they are not in a position to meet the >> >>> requirements because they are not in scope for >> >>> their work. Of course the deliverable teams will >> >>> work with additional requirements next to the >> >>> ones mentioned in the UCR document. Those >> >>> additional requirements will be based on general >> >>> best practices. I think the UoM and precision >> >>> requirements fall in that class.____ >> >>> >> >>> ____ >> >>> >> >>> That said, perhaps there is a way to shape the >> >>> requirements in such a way that they can be >> >>> included in the UCR document, without violating >> >>> the spatial scope constraint too harshly. After >> >>> all, it has been done for other requirements too, >> >>> to be honest.____ >> >>> >> >>> ____ >> >>> >> >>> Let's start with the UoM requirement (A). I >> >>> assume that is about the UoM of coordinate data >> >>> only. I think this is already implicitly covered >> >>> by the CRS requirements Linking geometry to CRS >> >>> <http://w3c.github.io/sdw/UseCases/ >> SDWUseCasesAndRequirements.html#LinkingCRS>, >> >>> Determinable CRS >> >>> <http://w3c.github.io/sdw/UseCases/ >> SDWUseCasesAndRequirements.html#DeterminableCRS> >> >>> and CRS definition >> >>> <http://w3c.github.io/sdw/UseCases/ >> SDWUseCasesAndRequirements.html#CRSDefinition>: >> >>> If those requirements are met, it should always >> >>> be possible to know the UoM of coordinates, >> >>> because the UoM will be part of the CRS >> >>> definition. Perhaps we should be explicit in >> >>> mentioning that a CRS definition should include >> >>> an indication of UoM?____ >> >>> >> >>> ____ >> >>> >> >>> As for the requirement B, if we change the >> >>> wording a bit the requirement could be made >> >>> applicable to spatial data only and therefore be >> >>> in scope:____ >> >>> >> >>> ____ >> >>> >> >>> B2) The use of precision that matches uncertainty >> >>> in coordinate data should be facilitated and >> >>> encouraged____ >> >>> >> >>> ____ >> >>> >> >>> With this kind of wording I think the BP editors >> >>> have a fighting chance of meeting the >> >>> requirement.____ >> >>> >> >>> ____ >> >>> >> >>> Please share your thoughts...____ >> >>> >> >>> ____ >> >>> >> >>> Regards,____ >> >>> >> >>> Frans____ >> >>> >> > >> > >> >> -- >> Andrea Perego, Ph.D. >> Scientific / Technical Project Officer >> European Commission DG JRC >> Directorate B - Growth and Innovation >> Unit B6 - Digital Economy >> Via E. 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Received on Friday, 9 September 2016 12:41:51 UTC