Re: Data Quality Vocab for SDW

Hi, Antoine.

I went through the 7 Apr 2016 version of DQV, and I saw that in Section 
5.13 ("Express dataset precision and accuracy") the examples include one 
on spatial resolution :)

http://w3c.github.io/dwbp/vocab-dqg.html#ExpressDatasetAccuracyPrecision

I have a couple of questions - mainly to better understand how spatial 
resolution can be modelled in DQV:


1. The first is specifically related to the "spatial resolution as 
distance in metres" example. The example specifies explicitly the unit 
of measure used:


:myDatasetPrecision a dqv:QualityMeasurement ;
   dqv:hasMetric :spatialResolutionAsDistanceInMetres ;
   dqv:value "1000"^^xsd:decimal ;
   sdmx-attribute:unitMeasure 
<http://www.wurvoc.org/vocabularies/om-1.8/metre>

:spatialResolutionAsDistanceInMetres a dqv:Metric;
   skos:definition "It expresses dataset resolution as distance in 
Metres"@en ;
   dqv:expectedDataType xsd:decimal ;
   dqv:inDimension dqv:precision


So, I wonder whether it'd rather be re-written as:


dqv:QualityMeasurement ;
     dqv:hasMetric :spatialResolutionAsDistance ;
     dqv:value "1000"^^xsd:decimal ;
     sdmx-attribute:unitMeasure 
<http://www.wurvoc.org/vocabularies/om-1.8/metre> .

:spatialResolutionAsDistance a dqv:Metric;
     skos:definition "It expresses dataset spatial resolution as 
distance"@en ;
     dqv:expectedDataType xsd:decimal ;
     dqv:inDimension dqv:precision .


In other words, the relevant instance of dqv:Metric needn't be bound to 
a specific unit of measure - or I'm wrong?

Also, I wonder how, by using this approach, it should be possible to 
specify spatial resolution as "equivalent scale" (e.g., 1:1,000, 
1:1,000,000, etc.) - i.e., with a fraction, without unit of measure. It 
would be great to have an example also on this!

I'm making a try below:


dqv:QualityMeasurement ;
     dqv:hasMetric :spatialResolutionAsEquivalentScale ;
     dqv:value "0.000001"^^xsd:decimal .

:spatialResolutionAsEquivalentScale a dqv:Metric;
     skos:definition "It expresses dataset spatial resolution as 
equivalent scale, by using a representative fraction (e.g., 1:1,000, 
1:1,000,000)."@en ;
     dqv:expectedDataType xsd:decimal ;
     dqv:inDimension dqv:precision .


Does this make sense?


2. As Rachel said earlier in this thread [1], the new ISO 19115 supports 
the possibility of specifying resolution as vertical or angular 
distance, and with level of detail.

Based on the DQV example, I guess the first two should be modelled as 
instances of dqv:Metric (:spatialResolutionAsVerticalDistance & 
spatialResolutionAsAngularDistance), whereas the level of detail should 
be specified with a dqv:QualityAnnotation (or a subclass - :LevelOfDetail).

Is this correct?


Finally, on a different note:

I think there's a typo in the following example (always Section 5.13):

:spatialAccuracy   a  dqv:Metric;
     skos:definition "It returns the percentage of spatial element that 
are found accurate acconding to  methodology XYZ"@en ;
     dqv:expectedDataType xsd:decimal ;
     dqv:inDimension ldqd:semanticAccuracy


s/acconding/according/


Thanks!

Andrea

----
[1]https://lists.w3.org/Archives/Public/public-sdw-comments/2016Mar/0008.html


On 15/03/2016 16:42, Antoine Isaac wrote:
> Dear all,
>
> Just a brief note about this, to
> 1: thank you for the input!
> 2: warn you that we've noted an action [1] on creating an example with
> DQV that shows how we could represent your case.
> This may go as far as creating a specific instance of dqv:Dimension for
> granularity/precision.
>
> Cheers,
>
> Antoine
>
> [1] https://www.w3.org/2013/dwbp/track/actions/264
>
> On 3/9/16 2:37 PM, Heaven, Rachel E. wrote:
>> Noting also that in the latest version of ISO 19115 (ISO 19115-1:2014)
>> the spatial resolution of a dataset can also be expressed as a
>> vertical distance, an angular distance (gco:Angle), or as
>> levelOfDetail (gco:CharacterString), in addition to the previous
>> options of distance (=horizontal ground distance) or equivalent scale.
>>
>> Cheers,
>> Rachel
>>
>> -----Original Message-----
>> From: Andrea Perego [mailto:andrea.perego@jrc.ec.europa.eu]
>> Sent: 09 March 2016 10:23
>> To: Antoine Isaac
>> Cc: Phil Archer; Linda van den Brink; Riccardo Albertoni;
>> 'public-sdw-comments@w3.org'
>> Subject: Re: Data Quality Vocab for SDW
>>
>> Hi, Antoine.
>>
>> I can contribute a use case concerning geospatial metadata.
>>
>> One of the information that is typically included concerns the spatial
>> resolution of a dataset. This is expressed either by a distance -
>> e.g., data have a 1km resolution - or with an equivalent scale (i.e., a
>> fraction) - e.g., 1:1,000,000.
>>
>> I include below two XML code snippets to show how this is expressed in
>> ISO 19115:
>>
>>
>> Spatial resolution as distance (1,000 m):
>>
>> <gmd:spatialResolution>
>>     <gmd:MD_Resolution>
>>       <gmd:distance>
>>         <gco:Distance
>> uom="http://standards.iso.org/ittf/PubliclyAvailableStandards/ISO_19139_Schemas/resources/uom/ML_gmxUom.xml#m">1000</gco:Distance>
>>
>>       </gmd:distance>
>>     </gmd:MD_Resolution>
>> </gmd:spatialResolution>
>>
>>
>>
>> Spatial resolution as equivalent scale (1:1,000,000):
>>
>> <gmd:spatialResolution>
>>     <gmd:MD_Resolution>
>>       <gmd:equivalentScale>
>>         <gmd:MD_RepresentativeFraction>
>>           <gmd:denominator>
>>             <gco:Integer>1000000</gco:Integer>
>>           </gmd:denominator>
>>         </gmd:MD_RepresentativeFraction>
>>       </gmd:equivalentScale>
>>     </gmd:MD_Resolution>
>> </gmd:spatialResolution>
>>
>>
>> Property dct:conformsTo (or a specific subproperty to be defined) can be
>> used to specify the spatial resolution of a dataset / distribution, but
>> three things are missing:
>>
>> 1. How to model the notion itself of (spatial) resolution.
>>
>> 2. How to express in RDF quantity values (e.g., 1m, 2km, 3s, 4h, 5l) and
>> fractions.
>>
>> 3. How to glue #1 and #2
>>
>> Actually, solutions exist to address point #2 - as the QUDT vocabulary
>> [1] mentioned during our first joint call [2]. But, to the best of my
>> knowledge, there's currently no best practice on how to use them.
>>
>> This situation is also the reason why in GeoDCAT-AP the decision taken
>> was to dump spatial resolution into a free-text field - a provisional
>> "mapping" meant to be replaced in the future with a more appropriate
>> approach.
>>
>>
>> So, looking at DQV, I wonder whether dqv:QualityMeasure (and the related
>> properties and classes) are generic enough to model also this
>> information. E.g. (just trying):
>>
>>
>> a:Dataset dqv:hasQualityMeasure [ a dqv:QualityMeasure ;
>>     dqv:hasMetric :spatialResolutionAsEquivalentScale ;
>>     dqv:value "0.000001"^^xsd:decimal ] .
>>
>>
>> another:Dataset dqv:hasQualityMeasure [ a dqv:QualityMeasure ;
>>     dqv:hasMetric :spatialResolutionAsDistanceInMetres ;
>>     dqv:value "1000"^^xsd:decimal ] .
>>
>>
>> Not sure this is correct. In particular, it is unclear to me whether
>> this is the correct way (in DQV) of modelling the notions of resolution,
>> distance / equivalent scale, and units of measurement. In the examples
>> above, they are all merged together in one instance of dqv:Metric -
>> which, besides resulting in a strange N-headed beast (formally
>> speaking), is not scalable.
>>
>>
>> A final (general) note:
>>
>> In my understanding, spatial (as well as temporal) resolution can be
>> considered as a specific type of data granularity. From this
>> perspective, and in order to ensure consistency and interoperability, it
>> would be desirable to have a DQV-based approach to model the general
>> notion of granularity, that could then be used as a basis for specific
>> types (as spatial / temporal resolution).
>>
>>
>> Cheers,
>>
>> Andrea
>>
>> ----
>> [1]http://www.qudt.org/
>> [2]https://www.w3.org/2016/02/17-sdw-minutes
>>
>>
>> On 07/03/2016 08:08, Antoine Isaac wrote:
>>> Dear Phil, Linda,
>>>
>>> Thanks a lot for this. This is in fact quite an important requirement;
>>> I've flagged it as an issue at
>>> https://www.w3.org/2013/dwbp/track/issues/243
>>>
>>> It may however take some time to come back to you, as we still have many
>>> issues. Actually we had granularity in scope, when we started with DQV.
>>> But this was downplayed as the DWBP requirements were very vague then.
>>> Do you have some precise examples from SDW, i.e. showing what data would
>>> look like, and its problems?
>>>
>>> Best,
>>>
>>> Antoine
>>>
>>> On 3/3/16 10:46 AM, Phil Archer wrote:
>>>> Antoine, Riccardo,
>>>>
>>>> As Antoine will recall, the Spatial Data WG, here represented by
>>>> Linda, has a particular interest in the DQV. An issue that comes up a
>>>> lot in spatial datasets is that of precision and accuracy (the fact
>>>> that Magna Carta was signed in 1215 is accurate, just not very
>>>> precise, saying it was signed at 1215-06-15T00:00:00 is precise but
>>>> inaccurate). It occurs in general datasets too but it's particularly
>>>> acute for spatial.
>>>>
>>>> On last night's SDW call, I was asked to put you in touch with linda
>>>> specifically to talk about this, in particular, how you might express
>>>> these ideas in the DQV?
>>>>
>>>>
>>>> Process note: I'm archiving this in the SDW's public comment list to
>>>> avoid having to sign you all up to yet another mailing list.
>>>>
>>>> For tracker this is ACTION-149
>>>>
>>>
>>
>> --
>> Andrea Perego, Ph.D.
>> Scientific / Technical Project Officer
>> European Commission DG JRC
>> Institute for Environment & Sustainability
>> Unit H06 - Digital Earth & Reference Data
>> Via E. Fermi, 2749 - TP 262
>> 21027 Ispra VA, Italy
>>
>> https://ec.europa.eu/jrc/
>>
>> ________________________________
>>   This message (and any attachments) is for the recipient only. NERC
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-- 
Andrea Perego, Ph.D.
Scientific / Technical Project Officer
European Commission DG JRC
Institute for Environment & Sustainability
Unit H06 - Digital Earth & Reference Data
Via E. Fermi, 2749 - TP 262
21027 Ispra VA, Italy

https://ec.europa.eu/jrc/

Received on Saturday, 9 April 2016 22:40:11 UTC