5. The method of claim 3 , wherein the user's manipulations comprise adding content to the document and deleting content from the document, comprising assigning a topic to the document based upon content added to or deleted from the document, and wherein the step of maintaining the affinity variable comprises updating the affinity variable for the topic assigned to the document based upon the added or deleted content.
3. The method of claim 1 , comprising updating the affinity variable for a topic based upon the user's manipulation of a document to which the topic is assigned.