Determining user presence using context in a decentralized unified messaging system (IPAD-UMS)

1. I TRODUCTIO UMS can be described as a system that allows for communication between users via a number of communication technologies over heterogeneous network infrastructures[1]. It integrates networking technologies such as Ethernet, ATM, IEEE 802.11, GSM and UMTS alongwith various devices such as laptops, tablet PCs, desktops, mobile phones, smartphones, PDAs, fax machines and landline phones. In other words, it allows the users to access their different types of messages by logging into one inbox from these different devices[2]. The user is able to create, modify, access and administer messages belonging to various formats on a single device to which he/she has immediate access. This form of ‘anywhere’, ‘anytime’ access to ‘anykind’ of messages enables the UMS to become ubiquitous and pervasive[3, 4].