Piggydb is an open source Web note-taking application that provides you with a platform to build your knowledge personally or collaboratively.
With Piggydb, you can create highly structured content by connecting knowledge fragments to each other to build a network structure, which is more flexible and expressive than a tree structure. Fragments can also be classified using hierarchical tags.
Piggydb does not aim to be an input-and-search database application. It aims to be a platform that encourages you to organize your knowledge continuously to discover new ideas or concepts, and moreover enrich your creativity.