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Distributed and Self-organizing Systems
Distributed and Self-organizing Systems

Towards Awareness and Control in Choreographed User Interface Mashups


Mashups utilizing publish-subscribe-based inter-widget communication approach do not require users to establish connections between widgets explicitly. Communication, i. e. data and control flows emerge as soon as widgets are put together in a workspace (so called choreographed user interface mashups, cf. [1]). Technically, this is achieved by employing the event-driven approach via publish-subscribe messaging pattern (pub/sub): widgets autonomously subscribe and publish messages on different communication channels, so-called topics. A message bus running within a browser takes care of delivering messages to all interested parties, i. e., widgets subscribed to the corresponding topics.

This, however, implies a lack of awareness and control by end users - an implication which was confirmed in the interviews and observations during the user studies [2]. A profound analysis of the described problems, analysis of possible solutions from related research fields and implications for the PubSub-based systems can be found in the corresponding paper [3].

The presented approach developed in the course of the OMELETTE project makes use of several extensions to the choreographed mashup composition model. For example, users are able to restrict communication between widgets using so called restrictions, i.e. block one-to-one or one-to-many connections between widgets. Available communication channels and publication-restrictions can be visualized by the platform in order to inform the user about which widgets exchange which data.

Online Demo

To try out the demo, click on the icon on a widget border and select "Show/Hide Communications". To prevent the widget from receiving or sending messages select "Isolate Widget". To block a direct connection between two widgets click on the corresponding arrow. Hover the mouse over it to see which message types (topics) are transferred between the widgets.


Further Readings

[1] Scott Wilson, Florian Daniel, Uwe Jugel and Stefano Soi. Orchestrated User Interface Mashups Using W3C Widgets. ICWE 2011 Workshops, June 2011, Springer, Pages 49–61.

[2] The OMELETTE Project (FP7/2010-2013 GA n 257635). D7.4 - evaluations of demonstrators report. Public deliverable, 2013.

[3] Olexiy Chudnovskyy, Stefan Pietschmann, Matthias Niederhausen, Vadim Chepegin, David Griffiths, Martin Gaedke. Awareness and Control for Inter-Widget Communication: Challenges and Solutions (Conference Paper) Proceedings of 13th International Conference on Web Engineering (ICWE2013). Aalborg, Denmark. July 08-12, 2013

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