CODEWITHSUNDEEP
owlontology
moondaisy
moondaisy

Reputation: 4481

OWL punning to represent a placeholder or abstract class

I'm trying to develop an ontology to represent a curricula, and in this curricula a student must take 6 elective courses (and has a long list of courses from which to choose).

Right now I have this classes:

- Course
--- Elective (defined class by isElective = true && type = Course)

And all my possible elective courses are instances of the type Course with the data property isElective set to true.

But I want to represent that this 6 elective courses must be taken in a certain way, for instance, a student needs to take 4 of this courses on the last year (Year is a class) of the curricula.

I have been thinking of how to define this placeholder/abstract class, which as I have read isn't possible and doesn't make sense, and came across punning but I don't know if it is what I'm looking for.

Let's say I define a subclass of Course called ElectivePlaceholder, and then then 4 instances of this class where:

ElectiveX instanceOf ElectivePlaceholder
Year5 instanceOf Year
ElectiveX isPartOf Year5

Then I want to have a way to represent that a student choose to take AdvancedMaths (instance of Elective, aka instance of Course with isElective set to true) as it's ElectiveX.

How would I do that? Would punning be useful? Since it allows an object to treated as both a class and an individual.

Update

What I'm trying to model is not what a student chooses but the curricula itself.

Each curricula individual has different requirements as to how many elective courses the students must undertake and in which years. I need to represent this in a way either on the Curricula individual or the Year individual (so it can be inferred for the Curricula).

Right now:

YearX partOf CurriculaX

Upvotes: 0

Views: 255

Answers (1)

Henriette Harmse
Henriette Harmse

Reputation: 4787

Punning will not solve your problem. Punning allows you to refer to say Course as both an OWL class and an OWL individual.

You can achieve your desired result by defining your ontology as follows:

ObjectProperty: hasCourse
    Domain: Curricula
    Range: Course

Class: Curricula
    SubClassOf: 
        taughtInYear some xsd:integer,
        hasCourse some Course 

Class: CurriculaDifficult
    SubClassOf: 
        Curricula,
        hasCourse min 4 ElectiveCourse,
        hasCourse max 9 Course

Class: CurriculaEasy
    SubClassOf: 
        Curricula,
        hasCourse min 1 ElectiveCourse,
        hasCourse max 3 Course

Class: ElectiveCourse
    SubClassOf: Course    
    DisjointWith: NonElectiveCourse

Class: NonElectiveCourse
    SubClassOf: Course    
    DisjointWith: ElectiveCourse

Class: Course

Individual: AdvancedMaths
    Types: ElectiveCourse

Individual: curriculaEasy2018
   Types: CurriculaEasy

   Facts:
     taughtInYear 2018,
     hasCourse someCourseA,
     hasCourse someCourseB,
     hasCourse someElectiveCourseA        

Class Student:
  SubClassOf: takeCurricula some Curricula

Individual: student123
   Types: Student
   Facts:
      takeCurricula curriculaEasy2018

A couple of things to note are:

(1) Abstract classes (that are well regarded programming concepts) cannot be represented in OWL. I explain some surprising things that OWL lacks coming from a programming background here.

(2) Rather than having isElective as a property that you associate with a Course it is better to model it as ElectiveCourse versus NonElectiveCourse that are disjoint. Reason being that if you ever want to extend the definition of NonElectiveCourse you can do that. This is also in coding the reason why it is best to avoid flags.

(3) You have to close your Curricula in some way by stating what the maximum number of courses are otherwise, due to the open world assumption, the reasoner will have no way to know that you have not specified at least 4 ElectiveCourses. I have written about this here.

** UPDATE ** So you can add CurruculaEasy and CurruculaDifficult classes with different numbers of requirements for electives as shown above. You can add a Curricula that is the super class of CurruculaEasy and CurriculaDifficult. For Curricula you add that it subclasses taughtInYear some xsd:integer as shown above.

Upvotes: 2

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