Middleware 2003

ACM/IFIP/USENIX International Middleware Conference

Rio Othon Palace Hotel

Rio de Janeiro, Brazil

16-20 June 2003

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Full Paper Abstracts

Supporting Mobility in Content-Based Publish/Subscribe Middleware

Ludger Fiege, Felix Gaertner, Oliver Kasten and Andreas Zeidler (TU Darmstadt)

Publish/subscribe (pub/sub) is considered a valuable middleware architecture that proliferates loose
coupling and leverages reconfigurability and evolution. Up to now, existing pub/sub middleware was
optimized for static systems where users as well as the underlying system structure was rather fixed.
We study the question whether existing pub/sub middleware can be extended to support mobile and
location-dependent applications. We first analyze the requirements of such applications and
distinguish two orthogonal forms of mobility: the system-centric physical mobility and an application-
centric logical mobility (where users are aware that they are changing location). For logical-mobility we
introduce location-dependent subscriptions as a suitable means to exploit the power of the event-based
paradigm in mobile applications. Briefly spoken, a location-dependent subscription offers to express
interest in all events which are related to a user's current location. We present efficient implementations
for both forms of mobility within the content-based pub/sub middleware Rebeca. Our solutions draw
much of their efficiency from the refined routing capabilities (namely, covering and merging) of the
Rebeca system.

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