Simple, unconnected knowledge fragments can be used as a personal journal or a diary, aided by the calendar interface, and you can use the full-text search facility to find and retrieve the information. However, as you connect ('relate') knowledge fragments to one another, the knowledge in your database becomes more useful and valuable.
Structurally the relationships between fragments resemble a network; this is less limiting than other types of relationship such as the tree structure, where each node can only have one parent. Piggydb allows relationships between fragments to be as complex as you need.
A well-built network of related fragments can be navigated easily using the Tree View, and arbitrary parts can be viewed using the Document View which renders in a "printer-friendly" format.