In this paper, we develop a formalism called a distributed constraint satisfaction problem (distributed CSP) and algorithms for solving distributed CSPs. A distributed CSP is a constraint satisfaction problem in which variables and constraints are distributed among multiple agents. Various application problems in Distributed Artificial Intelligence can be formalized as distributed CSPs. We present our newly developed technique called asynchronous backtracking that allows agents to act asynchronously and concurrently without any global control, while guaranteeing the completeness of the algorithm. Furthermore, we describe how the asynchronous backtracking algorithm can be modified into a more efficient algorithm called an asynchronous weak-commitment search, which can revise a bad decision without exhaustive search by changing the priority order of agents dynamically. The experimental results on various example problems show that the asynchronous weak-commitment search algorithm is, by far more, efficient than the asynchronous backtracking algorithm and can solve fairly large-scale problems.Index Terms-Backtracking algorithms, constraint satisfaction problem, distributed artificial intelligence, iterative improvement algorithm, multiagent systems.

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Reminiscence intervention is effective for increasing self-esteem and decreasing behavioural disturbances in individuals with dementia. This paper introduces the concept of a "personalised reminiscence photo video" as a convenient method for reminiscence intervention. The video utilises a slideshow video of personal photos with narration, background music, and pan/zoom visual effects. A group of 15 individuals with dementia watched personalised reminiscence photo videos as well as two types of TV shows: a variety show and a news show. Eighty percent of the subjects (12 out of 15) showed more attention to their personalised reminiscence photo video than to the other two types of TV shows, thus suggesting the effectiveness of personalised reminiscence photo videos for reminiscence intervention.

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We previously developed remote reminiscence conversation and schedule prompter systems via the videophone to improve psychological stability and to assist individuals with dementia to perform household tasks. Our results showed that the psychological stability of 1 patient persisted for 3 hours after remote conversations. The task completion rate afforded by the schedule prompter system, which displays a video reminder series automatically, was 52%. In the present study, we also investigated whether psychological stability was sustained in other patients. Furthermore, motivational prompter videos were added to enhance the original schedule prompter system. We found that 1 in 4 patients living at home showed greater stability while conversing with a conversation partner on the videophone than while watching television programs, and that she remained stable for 3 hours after remote conversations. The task completion rate afforded by the revised schedule prompter system was 82%. These 2 remote systems are promising tools for assisting individuals with dementia in their daily lives.