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Hi Radu,

On May 7, 2012, at 12:50 PM, Radu Silaghi wrote:

> 
> Hello all,
> 
> Has anybody a use case for gr:displayPosition at http://www.heppnetz.de/ontologies/goodrelations/v1.html#displayPosition ?
> 
> It is a new introduction and not officially documented yet, and I am new to GR and overwelmed at this.
> 
> thanks,
> 
> Radu

You can use this annotation property for indicating a preferred order for the rendering of various types of data. 
A typical example is defining an order for product attributes in a domain extension for GoodRelations.

For instance, if you follow the recipe at

     http://wiki.goodrelations-vocabulary.org/Documentation/Extensions


and define new product properties like

# Properties
foo:hasOperatingVoltage
    a owl:ObjectProperty ;
    rdfs:domain default:TVSet ;
    rdfs:range gr:QuantitativeValueInteger ;
    rdfs:subPropertyOf gr:quantitativeProductOrServiceProperty .
 
foo:hasVideoInput
    a owl:DatatypeProperty ;
    rdfs:domain default:TVSet ;
    rdfs:range xsd:boolean ;
    rdfs:subPropertyOf gr:datatypeProductOrServiceProperty .

then you may want to say that the operating voltage should typically be shown first by a client by adding the statements

foo:hasOperatingVoltage gr:displayPosition "1"^^xsd:integer .
foo:hasVideoInput gr:displayPosition "2"^^xsd:integer .

A client should (but does not have to) order property values by the ordering relation of indicated by gr:displayPosition, if present.

Note that this simple mechanism does allow only a single, global order at the vocabulary level.

The initial reason to introduce gr:displayPosition was that you often need to create a tabular list of opening hours per day of the week, which is difficult only on the basis of gr:hasNext and gr:hasPrevious links between the days of the week. Thus, all days of the week in GoodRelations have a gr:displayPosition property with Mo = 1, Tue = 2, Wed = 3, ..., Sun = 7.

# Example in Turtle syntax

gr:Monday a gr:DayOfWeek;
	gr:displayPosition 1;
...
	rdfs:label "Monday (day of week)"@en.

gr:Tuesday a gr:DayOfWeek;
	gr:displayPosition 2;
...
	rdfs:label "Tuesday (day of week)"@en.

etc.

This allows simple SPARQL queries like

SELECT DISTINCT(?day), ?pos WHERE 
{ ?day a gr:DayOfWeek . 
  ?day gr:displayPosition ?pos. } 
ORDER BY ?pos

which will return this nicely ordered list

day							pos
http://purl.org/goodrelations/v1#Monday			1
http://purl.org/goodrelations/v1#Tuesday		2
http://purl.org/goodrelations/v1#Wednesday		3
http://purl.org/goodrelations/v1#Thursday		4
http://purl.org/goodrelations/v1#Friday			5
http://purl.org/goodrelations/v1#Saturday		6
http://purl.org/goodrelations/v1#Sunday			7
http://purl.org/goodrelations/v1#PublicHolidays		8

If you use nested SPARQL queries, you can nicely create an ordered table of opening hours on the basis of gr:displayPosition.

Hope that helps.

Best wishes

Martin Hepp


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

e-mail:  hepp at ebusiness-unibw.org
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