figure and is_about

[Joe Behling]

I have an instance of an IAO figure

The instance has a corresponding .png which when viewed visually represents a chlorine molecule

I have the class "chlorine"

How do i express that the molecular drawing represents chlorine?

main problem that i am struggling with:

i cannot create an instance of the class chlorine and relate it to the figure using is_about because there is no real-world instance of the chlorine.

Thanks,

Joe

[Bill Duncan]

Here's my take:

The instance of the IAO figure is about the class chlorine.

The .png file is a concretization of the instance of the IAO figure.

-- Bill

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[Bill Hogan]

I agree, but you can't say that in OWL, because you cannot connect the instance (figure) to the class (chlorine) with the object property "is about".  OWL only lets you do such instance-class connections via rdf:type.

Many folks are using punning as a workaround: you create an OWL individual with the same IRI as the class for chlorine, and say that the figure is about the punned individual.  Most folks also say: punned individual IRI rdf:type punned class IRI.

The downside to the approach is that you could end up with large numbers of punned individuals, depending on how many figures (or other ICEs) you have on how many classes.  You also need to think carefully about how you do reasoning / query in such an approach.

Bill

[Bill Duncan]

Here are some other approaches besides punning:

1. Create an annotation property and use that to relate the instance of ICE to the chlorine class. The disadvantage of this is you can't do reasoning using the annotation property, but you can still do SPARQL queries on it. 

2. Use an anonymous class to say that your instance of the ice is about some instance of chlorine. In functional syntax, the OWL would look something like this (ice#1 is the instance of the ICE, chlorine is a class):

ClassAssertion(ObjectSomeValuesFrom('is about' chlorine) ice#1)

In this OWL statement, ice#1 isn't related the class itself, but it is related (via 'is about') to those things which are instances of chlorine. The advantage of this is that it does support reasoning. However, to write a SPARQL query for it, you have to use owl:onProperty, and this can be a pain to get correct.

I've used method #2, but I'm not sure it really necessary. If you don't need to rely on the reasoner, I would probably advocate for method #1. But I don't know the particulars of your project.

-- Bill