- Ubiquitous service
A service refers to a software component that performs computation or action on behalf of a system entity. This entity can be the user or another service. Services are usually well-defined in their functionality as well as their inputs and outputs [H. Ryu, GY Hong, and H. James. A Research on Quality Assessment Technique for Ubiquitous Software or Middleware. Technical Report 2004-1, Massey university, New Zealand, 2004 ] .
We identify the five goals of ubiquity, with regards to a service, as Availability, Transparency, Seamlessness, Awareness, and Trustworthiness (ATSAT) as depicted in the figure. These goals may be satisfied to varying degrees based on user needs and operating conditions.
Ideally, a ubiquitous service should be available independent context. The service should be also available regardless of changes in user status, needs, and preferences.
According to Weiser, a good tool is an invisible tool. Weisers notion of disappearance, where a tool is "literally visible, effectively invisible" means that the tool does not intrude on the user consciousness; the user focuses on the task, not the tool. Ubiquitous computing provides smarter unconscious, so that users do more easily and intuitively without requiring user attention and awareness of the underlying technology. Transparency implies more than just a user-friendly interface; the technology should facilitate the task in a non-intrusive way and in this way "hide" the underlying technology from the user [Louise Barkhuus. Ubiquitous computing: Transparency in context-aware mobile computing. In UbiComp 2002, Doctoral Consortium,Gothenborg, 2004. ]
Seamlessness can be defined as the capability of providing an everlasting service session under any connection with any device [Irene Y. L. Chen, Stephen J. H. Yang, and Jia Zhang. Ubiquitous provision of context aware web services. In Proceedings of the IEEEInternational Conference on Services Computing (SCC’06), pages 60-68, 2006] . The ultimate goal is that the system will recognize the user wherever she logs on, on any system, with any equipment, at any time, with the applications in a given state and have them adapt in the best possible way given these surrounding conditions. Seams occur when the service fails to satisfy the minimum QoS requirements set by the end-user.
Ubiquitous devices extend the human senses by providing greater awareness of the surrounding environment. By blending into the physical world, a ubiquitous service bridges the gap between the end-user and his surrounding. We advocate the need for mutual awareness between the user(context) and the service (feedback). Abowd and Mynatt [Gregory D. Abowd and Elizabeth D. Mynatt. Charting past, present, and future research in ubiquitous computing. ACM Trans. Computer-Human Interaction, 7(1):29–58, 2000.] put forth the "five W's" of context,providing a good starting point of the different components that should be put together to provide user context. The five Ws are:- Who (the ability of a device to identify not only its owner, but other people and devices in its vicinity within the environment), What (the ability to interpret user activity and behavior, and using that information to infer what the user wants to do), Where (the ability to interpret the location of the user and use that to tailor functionality), When (theability to understand the passage of time, use it to understand the activities around and to make inferences), and Why (the ability to understand the reasons behind certain user actions).In addition to the system awareness of its user, a ubiquitous environment provides user awareness of the task (i.e. feedback) in a way that may enhance the user's decisions.
We define trust of an entity in a ubiquitous service environmentas the confidence that the entity will behave as expected in a given context. Mutual trust must be established between different entities in a ubiquitous environment in a sense that each entity is assigned a trust value based on its behavior. An entity can be a device, a service or a user. In the latter case, the trustworthiness of a service or a device has psycho sociological aspects that affect its usability. The model of trust in a ubiquitous context should capture both the needs of thetraditional world of computing where trust is based on identity, and of the world of ubiquitous and pervasive computing where trust is based on identity, physical context or a combination of both [N. Shankar and W. Arbaugh. On trust for ubiquitous computing. In Workshop on Security in Ubiquitous Computing, Ubicomp 2002.] [cite paper| author = D. Quercia, S. Hailes, L. Capra | title = MobiRate: Making Mobile Raters Stick to their Word | publisher = ACM Ubicomp | date = 2008 | url = http://www.cs.ucl.ac.uk/staff/d.quercia/publications/quercia08mobirate.pdf] . In other words, both identity-based and context-based trust relationships should be defined between different entities within a ubiquitous environment.
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