RDF types for base types from ISO 19103 - measure types

[jechterhoff]

Description

INSPIRE application schemas use a number of classes from ISO/TS 19103:2005 as base types. As outlined in issue #9, a mapping to an RDF implementation must be found for each of the ISO 19103 types that is used in INSPIRE so that INSPIRE data can be encoded in RDF.

For the measure types from ISO 19103 (Angle, Area, Distance, Length, Measure, Probability, Velocity and Volume), a single mapping is most likely sufficient and could be used for all Measure data types from ISO 19103.

We also need a mapping for the type UnitOfMeasure.

NOTE: The model of ISO 19103 classes sometimes is rather elaborate. GML shows that an actual implementation of these types does not necessarily need to include all information defined for them. A mapping between the information items supported by a particular implementation schema (such as GML) to the conceptual schema (in this case ISO 19103) is also feasible. Due to restrictions of the implementation technology the mapping may even not be 100% complete.

NOTE: the following lists may provide useful starting points for the required mappings

• Mapping ‘Measure’:
  • http://www.qudt.org/qudt/owl/1.0.0/qudt/index.html#QuantityValue
  • http://idi.fundacionctic.org/muo/muo-vocab.html#term_QualityValue
  • http://jcgm.bipm.org/vim/en/1.19.html
• Mapping ‘UnitOfMeasure’
  • http://www.qudt.org/qudt/owl/1.0.0/qudt/index.html#Unit
  • https://www.w3.org/2005/Incubator/ssn/ssnx/qu/qu#Unit
  • http://idi.fundacionctic.org/muo/muo-vocab.html#term_UnitOfMeasurement

Discussion Item

Do you have a suggestion how the measure types from ISO 19103 can be mapped in an INSPIRE RDF implementation?

[jechterhoff]

QUDT appears to be a suitable candidate, specifically because of its industry and standards alignment (for further details, see the presentation on "NASA QUDT Handbook", page 36). The ontology is currently available in version 1.1.

According to various sources on the web, version 2.0 will be a major improvement. Some resources of QUDT v2.0 are published on http://www.linkedmodel.org/. However, I could not find any RDF representations (due to broken links). It is unclear when QUDT version 2.0 might be published. There has not been an update for a year.

[cportele]

There is a current (and growing) thread on unit of measurement aspects in the W3C/OGC Spatial Data on the Web working group that is related: https://lists.w3.org/Archives/Public/public-sdw-wg/2016Jun/0160.html

[jechterhoff]

Thanks for the pointer.
The blogpost http://composing-the-semantic-web.blogspot.de/2009/08/units-ontology-with-spin-support.html on QUDT is interesting. It shows that one can explicitly annotate a value with a specific unit (similar to how it's done in GML) and also use unit-specific datatypes with values such as "8380"^^unit:Centimeter. Then there are also SPARQL extension functions (implemented using the SPIN framework) to automatically convert units.

Now, the blogpost is from 2009, so I'm not sure how valid this is for QUDT 2.0 - which is still work in progress or under review.

[jechterhoff]

The Data on the Web Best Practices: Data Quality Vocabulary defines class Quality Measurement, where the usage note says:

The unit of measure in quality measurement should be specified through the property sdmx-attribute:unitMeasure as recommended by RDF Data Cube Vocab-Data-Cube. The Ontology of units of Measure (OM) [RijgersbergEtAl] provides a list of HTTP dereferenceable unit of measures, which can be exploited as values for sdmx-attribute:unitMeasure.

In DQV a quality measure is used to express dataset precision and accuracy.

[jechterhoff]

The draft INSPIRE vocabularies use a custom implementation of Measure that follows the simple approach from GML:

base:Measure
  a 					rdfs:Datatype ;
  skos:notation  "Measure"^^xsd:NCName ;
  skos:prefLabel "measure"@en ;
  skos:definition "a text representation of a measure value. The decimal value is followed by a space and the unit of the measure." .

Regarding measures and units of measure, the Spatial Data on the Web Best Practices document states [1] that:

• "There is no evidence of best practice here — nor is there consensus on which data model is best for describing units of measure."
• "The W3C Web of Things Interest Group has created a task force to address the challenges of semantic interoperability relating to units of measure, which may lead to emergence of best practices that can be adopted by spatial data publishers."

The draft INSPIRE vocabularies use a custom implementation of Sign:

base:Sign
  a                         rdfs:Datatype ;
  owl:oneOf                 ( "+" "-" ) ;
  skos:notation             "Sign"^^xsd:NCName ;
  skos:prefLabel            "sign"@en .

[1] https://www.w3.org/TR/sdw-bp/#c-unitofmeasure

[namedgraph]

Definitly voting for QUDT here. For example:

base:Measure rdfs:subClassOf qudt:QuantityValue

[namedgraph]

Also worth considering qb:Observation from RDF Data Cube:
https://www.w3.org/TR/vocab-data-cube/#reference-observations