A Scalable Middleware for Presence Virtualization and Federation

Abstract. Presence is a key enabling technology for developing rich
context-aware applications. However, there is no general purpose pres-
ence infrastructure available today which is both flexible and highly scal-
able to cater to a wide range of end users (consumers) and applications.
We have introduced earlier [12], the concept of virtual presentities (log-
ical presentities created in response to applications or user queries to
presence systems) and a middleware for the life-cycle management of
the virtual presentities, that leverages the presence infrastructure in a
programmatically flexible and scalable fashion. Given the exponential
rise in the number of presence sources and the rapid emergence of so-
phisticated context-aware applications, the scalability of the middleware
is critical to its efficiency and general acceptability. In this paper, we
present the design to improve scalability further. A scalability measure,
inherent to the system design, is the representation of the presence logic
in applications and those used by end users as persistent queries on pres-
ence data, or the virtual presentities, for potential re-use among multi-
ple applications and end users with identical requirements. This reduces
the effective load on the base presence servers and thereby enabling it
to support more queries. Another scalability measure is to enhance the
life cycle management of the virtual presentities with the introduction
of hierarchical data re-utilization strategy. Besides enhancing the scal-
ability of the virtualization middleware, we have expanded its range of
operation by federating multiple presence domains and thereby enabling
applications and users making use of presence data from different het-
erogeneous, but independent presence domains. In this paper, we present
the detailed design, implementation and performance evaluation of the
enhanced middleware, highlighting the different measures adopted for
scalability and present experimental results to corroborate them.
Keywords: Presence, context, virtualization, scalability, federation

By: Arup Acharya, Xiping Wang, Nilanjan Banerjee, Dipanjan Chakraborty, Koustuv Dasgupta, Shachi Sharma

Published in: RI09008 in 2009


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