This document outlines requirements for personal knowledge management tools based on an analysis of how knowledge workers take notes and manage information. The three main requirements are: 1) Personal knowledge management tools should allow step-wise formalization that balances the costs of authoring content with the benefits of easy retrieval. 2) Tools require a unified conceptual model that can accommodate different levels of formality and supports the conversion of content between representations. 3) Core functions include fast note entry, versioning, linking and grouping of notes, querying, and active assistance with maintenance tasks.