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Re: comments on WD-vocab-dcat-20130312

From: Andrea Perego <andrea.perego@jrc.ec.europa.eu>
Date: Sun, 07 Apr 2013 00:46:08 +0200
Message-id: <CAHzfgWDoo3zdnO3Hcw+D8-5opwfwD5vHg9iwsnsoLHajn+Vebg@mail.gmail.com>
To: Bill Roberts <bill@swirrl.com>
Cc: "public-gld-comments@w3.org" <public-gld-comments@w3.org>
I support Bill's proposal about spatial / temporal granularity. This is an
issue we too have in work of the European Commission on the RDF
representation of metadata of different types of information resources
(i.e., not only datasets).

As an example, we have a specific requirement on metadata concerning
geospatial resources. At the EU level, the metadata schema to be used is
defined in the framework of the INSPIRE Directive [1]. Such schema includes
the notion of the "spatial resolution" of a geospatial resource (i.e.,
either a dataset, a dataset series, or a service), which is defined as
follows in the regulation [2] (Part B, Section 6.2):

Spatial resolution refers to the level of detail of the data set. It shall
be expressed as a set of zero to many resolution distances (typically for
gridded data and imagery-derived products) or equivalent scales (typically
for maps or map-derived products).

An equivalent scale is generally expressed as an integer value expressing
the scale denominator.

A resolution distance shall be expressed as a numerical value associated
with a unit of length.

This notion is analogous to the one of spatial granularity, and, as noticed
by Bill, there's no recommendation on how to represent this.



On Fri, Apr 5, 2013 at 11:22 AM, 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?
> 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.
> 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.
>  Best regards
> Bill
> Bill Roberts, CEO, Swirrl IT Limited
> Mobile: +44 (0) 7717 160378 | Skype: billroberts1966 | @billroberts
> http://swirrl.com | http://publishmydata.com

Andrea Perego, Ph.D.
European Commission DG JRC
Institute for Environment & Sustainability
Unit H06 - Digital Earth & Reference Data
Via E. Fermi, 2749 - TP 262
21027 Ispra VA, Italy

DE+RD Unit: http://ies.jrc.ec.europa.eu/DE

The views expressed are purely those of the writer and may
not in any circumstances be regarded as stating an official
position of the European Commission.
Received on Saturday, 6 April 2013 22:46:56 UTC

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