Re: Scientific Measurements

Hi

Just a couple of answers to points that have been raised.

There is a move within the IVOA to convert the unit used into an extension of QUDT
http://www.astro.gla.ac.uk/users/norman/ivoa/unity/RELEASE-NOTES

QUDT is being used "in the wild" within the Open PHACTS project (upon which I work) and we recommend its use for this purpose.
http://www.openphacts.org/specs/2012/WD-rdfguide-20120823/
 Several life sciences datasets have been converted using QUDT. Although one of our data providers has also used the UNITS ontology
https://code.google.com/p/unit-ontology/
which we are mapping to the QUDT.

Alasdair


On 5 Jun 2013, at 23:29, Holger Knublauch <holger@topquadrant.com> wrote:

> Units of measurement are important for quality data, and IMHO the W3C missed the opportunity to include a clean mechanism for units into RDF or RDF Schema itself early on. As a result, vocabularies such as QUDT were created by 3rd parties (my employer TopQuadrant in this case) and RDF developers are still confused what to do.
> 
> Maybe schema.org can do a better job. Just some random input. With QUDT some of the use patterns are to
> 
> - use the units as XSD datatype of the RDF literals (this would not work with schema.org right now, because the datatypes there are a fixed enumeration while in RDF this is open-ended).
> 
> - use "reified" objects that are pairs of a value plus another property for the unit.
> 
> - attach the (default) unit to the property itself. This makes computations based on those values easiest because no normalization needs to be done, but obviously not everyone (e.g. in the US) would be happy to convert everything into metric units and prefer to use units such as feet.
> 
> A 4th option is used by schema.org in some places, allowing values to be strings consisting of a number plus a unit's abbreviation, e.g. "10 ft".
> 
> I do believe that there is no harm (but many benefits) if the schema.org properties would point to a default unit so that people just need to enter a number as the property value. This could be part of a comment, but better would be a property attached to the property itself. If another unit than the default is needed then the string encoding (option 4) might be the most pragmatic approach. Engines that use schema.org data could quite easily translate those values into proper, normalized RDF literals before writing them into an RDF triple store. Ontologies such as QUDT would be useful for such normalizations because they already contain the unit abbreviations and their conversion factors in (SPARQL-friendly) machine readable form. I had written up details on how to achieve that with SPIN here
> 
> http://composing-the-semantic-web.blogspot.com.au/2009/08/units-ontology-with-spin-support.html
> 
> In general, I see the role of schema.org twofold: for collecting data schema.org should make it easy for people to use, and therefore support flexibility in how such values are encoded as strings. But for processing and storing data, a normalized, strict version of schema.org can be used.
> 
> HTH
> Holger
> 
> 
> On 6/6/2013 6:08, William L. Anderson wrote:
>> And just to add to the soup there is Catalog QUDT: The QUDT, or 'Quantity, Unit, Dimension and Type' collection of ontologies define base classes, properties, and instances for modeling  physical quantities, units of measure, and their dimensions in various measurement systems.
>> 
>>   http://www.linkedmodel.org/catalog/qudt/1.1/index.html
>> 
>> -Bill Anderson
>> 
>> 
>> 
>> On Jun 5, 2013, at 12:35 PM, Alex Milowski <alex@milowski.com> wrote:
>> 
>>> 
>>> 
>>> On Wed, Jun 5, 2013 at 10:04 AM, Thad Guidry <thadguidry@gmail.com> wrote:
>>> 
>>> But that Type stems from eCommerce & Trade ... but it's all primarily based on UNECE codes... and those happen to have Measurements defined even scientific ones if you dig deep enough in it.
>>> 
>>> See the "master list" here: http://www.unece.org/cefact/xml_schemas/index.html  and scroll down and you will see the UNECE MeasurementUnit sections and others.
>>> 
>>> 
>>> BTW, poke me in eye with a red hot poker for making me read an XML Schema to find a three letter code.  ;)
>>> 
>>> Too bad they (or schema.org) doesn't have a flat list of the codes.
>>>    -- 
>>> --Alex Milowski
>>> "The excellence of grammar as a guide is proportional to the paucity of the
>>> inflexions, i.e. to the degree of analysis effected by the language
>>> considered."
>>> 
>>> Bertrand Russell in a footnote of Principles of Mathematics
>> 
> 
> 

Dr Alasdair J G Gray
Research Associate
Alasdair.Gray@manchester.ac.uk
+44 161 275 0145

http://www.cs.man.ac.uk/~graya/

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