A framework for contextual mediation in mobile and ubiquitous computing applied to the context-aware adaptation of maps

Chalmers, D., Dulay, N., and Sloman, M. 2004. A framework for contextual mediation in mobile and ubiquitous computing applied to the context-aware adaptation of maps. Personal Ubiquitous Comput. 8, 1 (Feb. 2004), 1-18.

The authors present “contextual mediation” as an approach to meeting needs and limits arising from context. They illustrate it with a context-aware map application and present experimental results and experiences which demonstrate that contextual mediation enhances the usability of the application in restrictive contexts of use.

Contextual mediation operates by selecting the most appropriate subset of the offered data in order to satisfy a request. This is a form of application-aware adaptation. Different users, in different contexts, will have differing preferences. Mediation must be able to differentiate between useful and unwanted data and use this differentiation to meet goals, such as timely delivery, screen space availability and price limits.

The data to mediate are categorized as follow: A response to a request is called a document. It may be an area of a map, a Web page, etc. The semantic structure of a document is described by elements. In a map a feature would be described as an element, e.g. the river Thames, the M1, which would take types of river and road. The data realizing the document are referred to as variants.

Utility functions are used to select amongst element to define which are useful and which variants of these elements would be the best for a specific context as well as how much degradation the alternative variants cause. A degradation path will reflect the utilities of the data, such that the least important will be offered for degradation first. User contextual cues are location, speed of movement, task (e.g. delivery, tourist), activity (e.g. passenger, driver) and screen size.

The users studies was based on maps printed on cards as the map application developed had some technical, HCI and data distribution limitations. For most users the mediated maps were both faster to use and subjectively better.

The authors define six uses of contextual information:

• Contextual sensing: where the context is sensed, and information describing the current context
• Contextual augmentation: where context is associated with data
• Context triggered action: such as loading map data for the next location predicted
• Contextual mediation: use of context to modify services provided or the data requested to best meet the needs of the user arising form the context of the interaction
• Context aware presentation: adaptation of the user interface or the presentation of data.

Relation to my thesis: Mediation helps dealing with the multiple constraints (technological, economical, physical, human) of ubiquitous systems. It is the process of highlighting the most relevant information according to the context and avoid unnecessary data visualization clutter and network dependance (e.g. managing latency). However, their network model takes does not take into consideration connectivity issues into consideration (only fluctuant throughput). Interestingly, the map application was not used for user studies as some sort of post-prototype evaluation.

Relevant references:
Chalmers D, Sloman M and Dulay N (2001) Map adaptation for users of mobile systems. In: Proceedings of the 10th International World Wide Web Conference (WWW-10), Hong Kong, China, May 2001

Schmidt A, Aidoo KA, Takaluoma A, Tuomela U, van Laerhoven K and van de Velde W (1999) Advanced interaction in context. In: Proceedings of the 1st International Symposium on Handheld and Ubiquitous Computing (HUC’99), Karlsruhe, Germany, June 1999