function makeProduct(toConvert) {
    var product = {
          description:'',
          // ...
          rules: makeRules({
            onFoo(){ product.x = y; }
          })
        };
    angular.extend(product, toConvert);
        return product;
}

function makeRules(opts){
    return {
        onChange: function() {
            console.log("Applying global change rules: ", this);
                    opts.onFoo();
        },
        onInstantiation: function() {
            console.log("Applying instantiation rules: ", this);
        },
        onContextApplication: function(room) {
            this.context = room;
            console.log("Applying context rules: ", this, room);
        },
    }
};