When it comes to fighting spam, Bayesian and ontological approaches are not mutually exclusive.
They could be used together in a highly complimentary fashion.
For example you could use Bayesian approaches, as they are implemented today, to build a spam ontology. In other words, the Bayesian approach would be extended through the addition of knowledge-representation methods for fighting spam.
This is almost the opposite of the Wikipedia-based approach I blogged about recently.
In the Wikipedia-based approach, the ontology consists of ham-based knowledge.
In the alternative I’ve presented here, the ontology consists of spam-based knowledge.
Both approaches are technically viable. However, it’d be interesting to see which one actually works better in practice.
Either way, automated approaches for constructing ontologies, as I’ve outlined elsewhere, are likely to be of significant applicability here.
Another point is also clear: Either way, this will be a computationally intensive activity!