Types are foundation of knowledge reuse in KF. You can specify that an item is of type 'another item'. Any item can act as a type of any other item of the same class (document, object, action or event). For example, you just finished a project P1, and used KF to describe its component structure, the actions taken and the failures or issues found. You then start a new project P2 that is similar so you tell KF that P2 is of type P1. P2 then inherits from P1 all its tasks and issues, in the form of checklists and potential defects.