How to check for correctess while using units?

[jdacoello]

This question refers to the practical use of a QuantityKind and the expected Unit. According to the ontology, each individual of QuantityKind has asserted a list of multiple units that are expected via the applicableUnit object property.

For example, the quantity kind velocity has the following applicable units:

• KiloM-PER_HR
• MI-PER_HR
• etc...

I am wondering if, while using the ontology in practice, there is a way to avoid using the wrong unit.

For example:
A custom ontology has the concept of Speed. To add context to the values that are measured from this signal, the custom ontology reuses the qudt quantity kind of velocity

eg:Speed qudt:hasQuantityKind qudt:Velocity .

What happens if someone by mistake uses the unit DEG_C (Degrees Celsius), which is of the kind Temperature instead of one of the expected units for velocity?
In other words, what is the proper way to check for correctness?

Thanks!

[steveraysteveray]

One quick way is to check the DimensionVector that a Unit points to, to check if it is the same as the DimensionVector pointed to by the QuantityKind. That at least tells you if the Unit and the QuantityKind are compatible.

Your example would fail that test.

[jdacoello]

I see. Then, @steveraysteveray is this test that you mention implemented..

• ..via SHACL?
• ..with a simple SPARQL query in the application that uses the data?
• ..other way?

Would you mind writing back a toy example?

Thank you!

[steveraysteveray]

Here's a simple SPARQL query to test unit:DEG_C. It's not efficient, with all those OPTIONAL statements, but gives you the idea.

PREFIX qk: <http://qudt.org/vocab/quantitykind/>
PREFIX qkdv: <http://qudt.org/vocab/dimensionvector/>
PREFIX qudt: <http://qudt.org/schema/qudt/>
PREFIX unit: <http://qudt.org/vocab/unit/>

SELECT  *
WHERE {
  BIND (unit:DEG_C as ?unit) .
  OPTIONAL {?unit qudt:hasQuantityKind ?qk .}
  OPTIONAL {?unit qudt:hasDimensionVector ?uVec .}
  OPTIONAL {?qk qudt:hasDimensionVector ?qVec .}
#  FILTER (?uVec != ?qVec) .
}

I commented out the FILTER statement so you could just see the values. You could turn this into a SHACL validation query by including the FILTER statement and putting the whole thing inside a SHACL shape.

[steveraysteveray]

Actually, I took another look with this query (no OPTIONAL statements) and found 5 offending situations, so thanks for leading me down this path!

SELECT  *
WHERE {
  ?unit a qudt:Unit .
  ?unit qudt:hasQuantityKind ?qk .
  ?unit qudt:hasDimensionVector ?uVec .
  ?qk qudt:hasDimensionVector ?qVec .
  FILTER (?uVec != ?qVec) .
}

Results:

[jhodgesatmb]

Since applicableUnit will always return a valid unit for a quantitykind the temperature example would fail since Deg_C would not be in the applicableUnit list. The particular example of Speed does need to be addressed but it is an anomaly (hopefully). In general, SHACL could be used in an application to test for validity, but the vocabularies are internally consistent. Jack

…

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On Feb 16, 2022, at 2:42 PM, steveraysteveray ***@***.***> wrote:  One quick way is to check the DimensionVector that a Unit points to, to check if it is the same as the DimensionVector pointed to by the QuantityKind. That at least tells you if the Unit and the QuantityKind are compatible. Your example would fail that test. — Reply to this email directly, view it on GitHub, or unsubscribe. Triage notifications on the go with GitHub Mobile for iOS or Android. You are receiving this because you are subscribed to this thread.

[jdacoello]

It seems that it is actually a good way to check for consistency within the ontology. Thank you for the examples. I’ll try to use something similar within a SHACL shape.

…

On 25. Feb 2022, at 7:46 PM, steveraysteveray ***@***.***> wrote:  Actually, I took another look with this query (no OPTIONAL statements) and found 5 offending situations, so thanks for leading me down this path! SELECT * WHERE { ?unit a qudt:Unit . ?unit qudt:hasQuantityKind ?qk . ?unit qudt:hasDimensionVector ?uVec . ?qk qudt:hasDimensionVector ?qVec . FILTER (?uVec != ?qVec) . } Results: — Reply to this email directly, view it on GitHub, or unsubscribe. You are receiving this because you authored the thread.