7. The system of claim 1 comprising a topic detector arranged to automatically detect at least one topic of a document of the document repository and to save the topic as an annotation of a node of the graphical structure and/or as an annotation of the document in the document repository.
7. The system of claim 1 comprising a topic detector arranged to automatically detect at least one topic of a document of the document repository and to save the topic as an annotation of a node of the graphical structure and/or as an annotation of the document in the document repository. 10. The system of claim 7 comprising a user node topic aggregator arranged to aggregate or select amongst topics of documents of the document repository which have been authored or consumed by the same user, the topics of the authored or consumed documents having been automatically detected by the topic detector.