I'm trying to write a very simple cms (for learning purposes) in kohana 3 web framework. I have my db schemas and i want to map it to ORM but i have problems with relations.

Schemas:articles and categories

One article has one category. One category might has many articles of course.

I think it is has_one relationship in article table.(?)

Now php code. I need to create application/classes/models/article.php first, yes?

class Model_Article extends ORM
{
    protected // and i am not sure what i suppose to write here       
}