Is there any relation between the class that implements interface and that interface?

Question

Consider this class hierarchy:

• Book extends Goods
• Book implements Taxable

As we know, there is a relationship

Answer 1

Well there's "supports-the-operations-of". Personally I don't find the "is-a", "can-do" etc mnemonics to be terribly useful. I prefer to think in terms of what the types allow, whether they're specialising existing behaviour or implementing the behaviour themselves etc. Analogies, like abstractions, tend to be leaky. If you know what the different between interface inheritance and implementation inheritance is, you probably don't need any extra phraseology to express it.