Zen Mind, Part 1
Dave McComb
We recently conducted a weeklong training session on OWL/DL and Ontology Engineering. Several of the participants would be attend the Semantic Technology Conference the following week, and felt they would get a lot more out of the conference because of the training. On drilling down a bit further, we found that the main benefit in this regard was breaking down their pre-conceived ideas of what semantics is. They were several days into the training before they were deprogrammed enough to completely follow what was going on.
In this article, I want to summarize some of these preconceptions and some ideas that will at least make you aware of them, and may help you get more out of any other studying you may be doing in the area. We call this “Zen Mind” from the Zen masters’ belief that to really learn you have to get as many preconceived ideas out of your head as possible long enough to establish some new patterns. I believe the Zen Masters called it “beginner’s mind.”
In that spirit, let us offer up some preconceived ideas and the “koans” (statements meant to elicit additional thinking) that seem to best address them.
Preconceived idea #1: Properties belong to Classes. People from a relational background make the partially correct analogy between relational attributes and semantic datatype properties, and between foreign key relationships in relational and object properties in semantics. However, this analogy will bite you. Repeatedly, as our students demonstrated.
They had a tough time remembering that the same property can be associated with many different classes. They were so used to each property being unique that, when they did associate the same property with more than one class, they gave it different names (locatedIn, became locatedInState, locatedInCountry, etc.).
The koans we decided were most useful in this case were two:
- Classes are really “sets.” To help get past the idea that classes are some sort of template, as they are in relational and Object Oriented technologies. This seems to help overcome the temptation to believe that the property belongs to the class.
- Properties own classes. When you define a restriction class in OWL/DL, what you have really done is use a pre-existing property to create a set of instances that have “someValues” from that property. It is the property that gives rise to the class, and therefore is more useful to think of the properties owning the classes – at least compared to the classes owning the properties.
So, if you find yourself relapsing into relational thinking, just repeat these two koans until the symptoms disappear.