DeepaMehta – A Semantic Desktop
Jo¨rg Richter2, Max Vo¨lkel1 and Heiko Haller1
1 AIFB, University of Karlsruhe, Germany
{mvo,hha}@aifb.uni-karlsruhe.de,
http://www.aifb.uni-karlsruhe.de/WBS
2 Co-Founder and Lead Architect of DeepaMehta, Berlin, Germany
jri@freenet.de, http://www.deepamehta.de
Abstract. DeepaMehta is an open source semantic desktop application
based on the Topic Maps standard. It’s conceptualization and especially
the UI have been guided by findings of cognitive psychology, in order
to provide a cognitively adequate working environment for knowledge
workers of all kind. It uses a graph visualization similar to concept maps.
DeepaMehta aims to evolve nowadays’ separated desktop applications
into an integrated workspace, enabling the user to organize, describe,
relate, edit and use almost any information objects.
Introduction In this paper we present the Topic-Map-centric semantic desktop
environment “DeepaMehta”. First we state some psychological requirements for
personal knowledge management (PKM). Then we describe the UI concepts
and their realisation via the Topic Map metaphor. We conclude with a brief
evaluation based on psychological criteria.
Psychological Requirements It should be the main goal of any knowledge
management software, to facilitate creation, externalisation, and (re)construction
of knowledge. Since there is evidence, that conceptual human knowledge is actu-
ally stored in an associative way, comparable to semantic networks [1], it appears
sensible to provide the knowledge worker with a UI, where contents are displayed,
managed, created, and refined in such an associative manner (i. e. items together
with their relations to other items), that enables the construction of semantic
networks—like concept maps [2, 3] do, as well as their more formal derivatives
knowledge maps[4].
Mapping Techniques3 allow the knowledge worker to use his natural sense of
spatial orientation wich easily distinguishes spatial positions and layouts (also
in a plane) to gain orientation in his knowledge space. Research in cognitive and
instructional psychology has shown, that the use of concept-map-like techniques
can have various positive effects on learning and problem solving—i. e. knowledge
generation and -use [5, 4, 6].
3 In this article the term “mapping” is used as coined in the domain of instructional
psychology, i. e. in the sense of creating and using visual knowledge representations
called “maps” like mind-maps, concept maps etc.

A major goal of user interaction design—especially in hypermedia—is to keep
cognitive overhead as low as possible. This is “the additional effort and concen-
tration necessary to maintain several tasks or trails at one time” [7]. Because
human working memory and thus capacity for conscious processing are quite
limited[8], we should avoid wasting it to secondary tasks like worrying about
saving files, dealing with layout and formatting or regaining orientation in the
information environment while writing the actual content.
Fig. 1. A Topic Map (typical DeepaMehta working screen)
Design The design of DeepaMehta is centered around the model of Topic Maps.
Topic maps are a human-oriented approach to encode knowledge and meta
knowledge (knowledge about knowledge). Topic maps consist of topics, asso-
ciations and occurrences. In the semantic web, this relates to resources, relations
and instances. Topic maps form a self-describing type system, much like RDF
schema. We assume some familiarity with Topic Maps and refer the reader to
ISO standard 13250 [9] and RDF [10].
DeepaMehta is an application framework with a Topic-Map-based UI (see
fig. 1), the design of which has been guided by findings in cognitive psychology.
Information of any kind as well as the relations between information items can
be displayed and edited in the same space. The user is no longer confronted with
files and programs. There are no overlapping windows, no menu bars and no
dialog boxes. Topic Maps are individual views on interconnected contents. An
application in this context is a collection of topic types, for which specialised and