Pressentials: A flexible middleware for presence-enabled applications

Abstract

Presence, broadly defined as an event publish-notification infrastructure based on unified communication protocols such as SIP or XMPP, is a key enabler for rich, contextual communication and collaboration. This paper presents the design, implementation and experimental evaluation of Pressentials - a large-scale presence federation and virtualization middleware for enabling context-aware applications. This middleware provides a programmatic interface for aggregating presence from various sources and for composing base presence information into abstract, functionally richer entities for enabling applications. An underlying design consideration is to leverage capabilities of protocols that are being widely deployed today. We present scaling algorithms used within the platform to re-use data and computation commonalities across multiple applications. To highlight the flexibility of the proposed framework, we discuss use-case scenarios (across multiple domains) built using this platform. © 2011 ACM.