This is the archive of the goodrelations dicussion list

Dear all:

This question may be relevant for a broader audience:
>
> I think I don't understand the usage of gr:hasUnitOfMeasurement in a 
> UnitPriceSpecification in general.
> If somebody is not sure whether the offering is a bundle (or if the 
> UnitPriceSpecification of a product can meaninfully refer to a "unit 
> or piece"),
> is it wrong to add the property "gr:hasUnitOfMeasurement" with the 
> value "C62"?
> Would it be better to add this property with C62 or ignore this 
> property completely?
>
> I only found one example in our wiki where the value of 
> hasUnitOfMeasurement is not C62 at
> http://www.ebusiness-unibw.org/wiki/GoodRelationsRental
>
Note that the Unit of Measurement is relevant in two aspects of an offer:
- First, it can be used to specify the quantities of individual 
components of a bundle.
- Second, it can be used to indicate the unit to which a price 
specification refers.

Example:

For a simple offer, you could say that you offer to sell 200 grams of 
salami and that the price was 20 euros per kilogram of salami. Then, the 
gr:UnitOfMeasurement attached to the gr:TypeAndQuantityNode is "grams" 
(GRM in UN/CEFACT) and the gr:UnitOfMeasurement attached to the 
gr:UnitPriceSpecification is "kilogram" (KGM in UN/CEFACT).

As soon as there is more than one component included in the offer, the 
only meaningful unit of measurement for the price specification is "C62" 
for unit or piece.

Example:

If you offer 200 grams of salami and 1 liter of beer for altogether 8 
euros, then you would use "GRM" and "LTR" for the two 
gr:TypeAndQuantityNode instances and "C62" for the unit price 
specification.

There can be rare cases of bundles that allow other units of measurement 
for the price specification, but as a rule of thumb, use C62 as soon as 
there is more than one component included the offer.

Relevant exceptions can be found for business functions other than 
gr:Sell - e.g. Rental: If you offer to rent out a pair of skis and 2 
tons of snow, then the price may be specified per hour (HUR in 
UN/CEFACT). But again, those cases are rare (yet still perfectly 
supported by GoodRelations).


Best wishes

Martin Hepp



--------------------------------------------------------------
martin hepp
e-business & web science research group
universitaet der bundeswehr muenchen

e-mail:  hepp at ebusiness-unibw.org
phone:   +49-(0)89-6004-4217
fax:     +49-(0)89-6004-4620
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         http://www.heppnetz.de/ (personal)
skype:   mfhepp 
twitter: mfhepp

Check out GoodRelations for E-Commerce on the Web of Linked Data!
=================================================================

Project page:
http://purl.org/goodrelations/

Resources for developers:
http://www.ebusiness-unibw.org/wiki/GoodRelations

Webcasts:
Overview - http://www.heppnetz.de/projects/goodrelations/webcast/
How-to   - http://vimeo.com/7583816

Recipe for Yahoo SearchMonkey:
http://www.ebusiness-unibw.org/wiki/GoodRelations_and_Yahoo_SearchMonkey

Talk at the Semantic Technology Conference 2009: 
"Semantic Web-based E-Commerce: The GoodRelations Ontology"
http://www.slideshare.net/mhepp/semantic-webbased-ecommerce-the-goodrelations-ontology-1535287

Overview article on Semantic Universe:
http://www.semanticuniverse.com/articles-semantic-web-based-e-commerce-webmasters-get-ready.html

Tutorial materials:
ISWC 2009 Tutorial: The Web of Data for E-Commerce in Brief: A Hands-on Introduction to the GoodRelations Ontology, RDFa, and Yahoo! SearchMonkey 
http://www.ebusiness-unibw.org/wiki/Web_of_Data_for_E-Commerce_Tutorial_ISWC2009