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Ontology Supported Systems Engineering: Classes or Instances?

Wrtitten by Ciset Gestor
Category: Technical Debates
31 January 2014

Thinking ontologies, what is the difference between a term being an instance of a class and a term being specialized from another term?

Systems Engineering has plenty of challenges today, and one of them, at least for me, is to improve the quality of the overall system and its associated life cycle work products. In The REUSE Company we are committed to produce processes, methods and tools for quality management (up to now in regards to Requirements) based on the application of Ontologies.

Using ontologies in Systems Engineering seems to be nice and fancy, but many problems arise, especially in regards to how system knowledge must be represented inside the ontology.

The content of this document is the first one of a series of topics that affect very much the engineers at The REUSE Company when designing tools for our customers.

In order to prepare the reader to understand our concern, I have to state that we have a strong debate in our little group of researchers and engineers regarding the following question:

Should a Systems Engineering ontology be represented using Classes or using Instances?

To make it clear, If our customer is developing a new airplane, for example the AX344, should the AX344 be represented in our ontology as a class named AX344 or as an instance of a class named AIRPLANE?

See in the following graph the representing possibilities:

Ontology Supported Systems Engineering: Classes or Instances?

Having:

Ontology Supported Systems Engineering: Classes or Instances?

First Solution: Class – Instance

Second Solution: Class-Class

Third Solution: Instance- Instance

Besides the structural differences between all the solutions (in the first one we use a relationship between one class and its instance, in the second one we use a relationship between two classes and in the third one we use a relationship between two instances). What is the difference at knowledge level? Isn’t it an AX344 an airplane in all the solutions?

In any case, the implemented solution in the Requirements Quality Suite for its version V14 will be the following:

The terminology in the ontology will always be at instance level and it will be possible to create, on demand, to instance – Class relationships between the instance terms in the ontology and new generated classes, only for grouping purposes.

See you in next post.

What is your opinion about this topic?

Language disclaimer:

Dear reader, unluckily for me, the native language inside my brain does not seem to be EnglishJ. This could mean that I am not very precise when stating my comments or ideas, or even worse, the syntax of my wording can be incorrect. If you are native English, please, try to forgive them thinking in how would you suffer answering to me in whatever language than yours. CheersJ

Author: Juan Llorens

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