Thanks for the replies. Bluesaga, yes you're right, I could have given a better example, maybe I can release an actual tutorial demonstrating how to use this for something practicle.

Also thanks for the comparison with Abstract classes dscreck - should help someone. I did want to fit this in, but I felt it would bulk out the article so I decided to keep it purely interface based.

__________________
Any fool can write code that a computer can understand. Good programmers write code that humans can understand.