Re: comments on WD-vocab-dcat-20130312

Dear Bill,

Thanks for your feedback on DCAT and sorry it took that long to reply!

Great to know that you find the DCAT document useful!
some further replies inline...

On 5 Apr 2013, at 10:22, Bill Roberts <bill@swirrl.com> wrote:

> I've also found the DCAT document very useful in providing advice on useful standardised metadata terms for describing linked data datasets. (I realise that DCAT is applicable to all kinds of datasets in data catalogues, but I have been applying it in a linked data context). 
> 
> I tend to use a combination of DCAT and VOID to describe such datasets - and generally always provide the minimum set of metadata described in the Data Cube draft (WD-vocab-data-cube-20130312 section 9) plus a few other useful items.
> 
> My comments on the Data Cube document mentioned the usefulness of coverage and granularity information (spatial and temporal) for describing datasets appearing in a catalogue.  This is particularly relevant for data cube datasets, but not only datacube datasets.
> 
> dct:spatial and dct:temporal handle the coverage question - that's fine.
> 
> Granularity is also a useful concept though - if you are looking for say crime statistics, there's a big difference in number of crimes for the whole country versus number of crimes per local government region or crimes per street.
> 
> This may be a complicated concept to describe reliably - in the data cube case, an option might be to use (as the value of some kind of granularity predicate) the class of the smallest type of area used in the values of the area dimension.  In other kinds of dataset it may be harder to define precisely.
> 
> Similarly, temporal granularity is of interest - whether data is provided annually, monthly, daily etc.  This is a separate concept from accrualPeriodicity as it's about the contents of the data not the frequency of update of the dataset.
> 
> Do the authors have ideas for potential standard terms to describe spatial and temporal granularity?
> 

Granularity was part of DCAT but it was removed later. One reason for removing it was that catalogues used it sparsely and inconsistently. Additionally, there was no clear demand for it and we had no concrete recommendation regarding what values can be used for it and whether a single property (granularity) is sufficient or whether two are needed (spatial and temporal granularity). It was decided not to include it in this version of DCAT and leave it as a possible future work.

> One other question: the range of accrualPeriodicity is a Frequency.  Looking into this recently, I found it hard to find a good set of standard URIs for frequencies (yearly, quarterly etc).  Can the authors recommend a standard set for use in this context?
> 
> Would it be easier if the predicate was rephrased as a period (updateInterval or something) rather than a frequency, as there are common terms for year, month etc that could be used as values.
> 

You can use the URIs defined as part of the Content Oriented Guidelines defined as part of the Data Cube work http://www.w3.org/TR/vocab-data-cube/#dsd-cog
Other URIs can be used and DCAT doesn't recommend any. However, t added this to the examples and linked to the Dat Cube document from DCAT Spec.

I agree that updateInterval sounds (much) clearer than accrualPeriodicity, but not sure if this alone justifies adding a new property. In favour of simplicity and consistency (within DCAT and in general), I suggested that we stick with the DCTerms property.

> I would also echo other recent comments on the list that a way of describing an API associated with a dataset would be useful, as a web service or API has some different characteristics to a downloadable file and to a certain extent needs different ways of describing it.

I added a short paragraph to the vocabulary overview section about APIs. DCAT basically cannot describe APIs beyond pointing to an access URL and related pages. It cannot for example describe the parameters to be used with the APIs, etc. Describing APIs was not originally a goal of DCAT and extending  DCAT to support that was not possible giving the resources and time available. 

Thanks again!

Best regards,
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Fadi Maali
PhD student @ DERI
Irish Research Council Embark Scholarship holder
http://www.deri.ie/users/fadi-maali
> 
> Best regards
> 
> Bill
> 
> 
> 
> 
> Bill Roberts, CEO, Swirrl IT Limited
> Mobile: +44 (0) 7717 160378 | Skype: billroberts1966 | @billroberts 
> http://swirrl.com | http://publishmydata.com
> 
> 
> 
>

Received on Tuesday, 25 June 2013 08:38:33 UTC