You have had enough of all the UML tools in the market, as they are all very cumbersome to use. Hence you have decided to design your own UML tool. However, during design, you realize that certain parts will be really complicated. For example, you have a Diagram object that is made up of lots of other objects. This diagram object can be used for creating a variety of other diagrams including class and sequence diagrams. When you create it you only want to specify its type and content. What design pattern should you use here?

In the Tips section, the tiers under N-Tier architecture need to be indented. Currently they are at the same indentation as the parent.