Re: Data Quality Vocab for SDW

Hi Andrea,

Thanks for your feedback, my replies are inline.

On 10 April 2016 at 00:39, Andrea Perego <andrea.perego@jrc.ec.europa.eu>
wrote:

> 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?
>
 You are right, I've changed it accordingly.


> 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?
>

It makes sense to me, I have added it in the example.



>
> 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?
>
Sorry, I am not sure to fully understand your question,  why  do you think
that the level of detail should be expressed as a Annotation?




>
>
> 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/
>
>
>
I have corrected it.
Many thanks.
Riccardo


> 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
>>> is subject to the Freedom of Information Act 2000 and the contents of
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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/
>



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