Naming a model class

[eluser]mattalexx[/eluser]
In the docs, it mentions this:

Code:

class Blogmodel extends Model {}

Then it mentions this:

Code:

class User_model extends Model {}

What's the best way to name my models? Should I use the underscore or not? If the object name has more than one word, which one is it?:

Code:

class Item_Image_model extends Model {}

Code:

class Item_image_model extends Model {}

Code:

class ItemImage_model extends Model {}

Code:

class ItemImageModel extends Model {}