I was last week invited as guest speaker at American University In Dubai (AUD) to present a lecture on “Design Patterns”. I presented two patterns namely “Command Pattern” and “Interceptor Pattern”. I gave a code based demonstration as well. The discussion got interesting while we were discussing interceptor pattern i.e when we talked about considering interceptor pattern for languages and grammers. I gave an example of a trading system that allows investors or traders to key in orders as text based queries instead of GUI based interaction.