Case Studies on Context-Aware Mobile Multimedia Services
Ojala, Timo, Journal of Digital Information Management
The research community has introduced a large volume of context-aware systems , which have adopted different definitions of the slippery notion of "context" . The systems typically involves mechanisms for context acquisition, preprocessing, representation, management and utilization in an application. The raw context data is acquired from different types of sources or "sensors", where the term "sensor' has to be understood very broadly. The raw context data may be subjected to different forms of preprocessing, for example to deal with missing data or to elicit higher level abstractions such as logical relationships or activities. Different models have been developed for representing context data in formats understood by computers and users, ranging from simple key-value pairs to extensive ontologies . Different types of centralized and distributed context management architectures have been proposed for storing and distributing context data to applications. They then utilize context for various purposes such as to adapting the user interface or to retrieving contextually relevant information.
When evaluating context-aware mobile systems, we have to make a distinction whether we evaluate the system architecture  or the user interface . Evaluating the user interface or usability of mobile systems is difficult due to extra interaction and evaluation challenges in the mobile domain. The interaction challenges include the mobile context of use, rich device functionality, small device size, lack of direct manipulation, and lack of standardization in handset and software design.
The evaluation challenges relate to data collection (technical, social and legal constraints) and uncontrollable variables (e.g. weather, ambient noise and attention destructors). Important decisions to be made regarding evaluation include what is evaluated (interface metaphors, mental models or UI elements), how (empirical vs analytical) and where (lab vs field). While a lab experiment does not provide a proper simulation of the true mobile context and the real-word factors affecting behavior and performance are missing, a field experiment in turn is time consuming, expensive, and suspect to data collection difficulties and uncontrollable external variables.
The six case studies presented in this paper demonstrate the utilization of context data in different types of context-aware mobile multimedia services. Each service employs a simple key-value context model and centralized context management architecture for storing or retrieving contextually relevant information. First five case studies originate from the Rotuaari --Context-Aware Mobile Multimedia Services research project . Each of them involved empirical evaluation in the field in form of a user evaluation with real users in true environment of use. It is a fundamental usability assessment method providing direct information about how the system is used and what are the exact problems . The sixth case study, panOULU Luotsi, is a joint effort of the Wireless Cities project  and the panOULU network . Some of the services are now in "production" use, either as a public service or as a commercial product.
SmartRotuaari was an early demonstration of the new mobile multimedia services that emerging wireless broadband Internet would eventually facilitate. SmartRotuaari comprised of a wireless multi-access network, SmartWare architcture for deploying context-aware mobile multimedia services, a web-based CPI (Content Provider Interface) for content management and a collection of functional prototype services . The design and implementation of the system started in 2002, leading to empirical evaluation in form of a large-scale field trial executed at downtown Oulu in fall 2003. SmartRotuaari was motivated by the needs of both companies (i.e. mobile service providers, technology providers, retailers etc. …