• Journal of Korea Multimedia Society
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• v.7 no.6
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• pp.832-840
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• 2004

In ubiquitous environments, context is any information that can be used to characterize the situation of an entity such as a person or an object. Many sensors and small computers collect contexts and provide applications with them. Thus, ubiquitous applications need to represent contexts and exploit them effectively. In this paper, we design and implement a context-aware messaging system, called UMS (Ubiquitous Messaging System), based on Java and Jini. UMS can represent various contexts using XML scripts, and communicate text messages regardless of user's location using the proxy mechanism of Jini.

• Journal of KIISE:Computer Systems and Theory
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• v.32 no.11_12
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• pp.617-628
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• 2005

The services for ubiquitous computing environments have to provide automatically user-specific adaptive services in dynamically changed environments with many informations provided by both a user and his/her environment. Workflows used in business and distributed computing environments support service automation by connecting many tasks with rules or orderings of tasks. Therefore we must specify context information on transition condition to support context-aware services by adapting a workflow to ubiquitous computing environments. In this paper, we present a structural context model to specify context information on transition constraints of the workflow. And we propose an uWDL Ubiquitous Workflow Description Language) based on web services, which provides web service interfaces which are standardized and independent on heterogeneous and various platforms, protocols, and languages. The uWDL tan be interpreted and executed by a workflow engine, and provide users autonomic services based on context-awareness.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.18 no.5
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• pp.71-81
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• 2008

In the paper, we designed a context aware task-role based access control system(CAT-RACS) which can control access and prevent illegal access efficiently for various information systems in ubiquitous computing environment. CAT-RACS applied CA-TRBAC, which adds context-role concept for achieve policy composition by context information and security level attribute to be kept confidentiality of information. CA-TRBAC doesn't permit access when context isn't coincident with access control conditions, or role and task's security level aren't accord with object's security level or their level is a lower level, even if user's role and task are coincident with access control conditions. It provides security services of user authentication and access control, etc. by a context-aware security manager, and provides context-aware security services and manages context information needed in security policy configuration by a context information fusion manager. Also, it manages CA-TRBAC policy, user authentication policy, and security domain management policy by a security policy manager.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.4B
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• pp.226-234
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• 2005

Context-Aware is the most important facts to reason a personalized and optimized service and to provide it to user. In the previous researches, user and surrounding environment were main facts of Context-Aware and middleware or center server has been proposed to support Context-Aware. In the daily space(for example, home, office, Car, etc), interactions between user and service can be a important facts of Context-Aware. In this paper, Context Autogenesis service model is introduced, simplified the Context-Aware process and designed the middleware which performs decentralize management for Context-Aware information of user's portable devices, so that problems occurred during the management and operation of existing Context-Aware system can be minimized and supporting user anonymity

• Journal of the Korean Institute of Intelligent Systems
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• v.16 no.4
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• pp.423-429
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• 2006

The systems in the ubiquitous computing environment need to provide users with context-aware services, intelligently interacting with the surrounding environment. Therefore, the systems in the ubiquitous computing environment require context-awareness ability in order to gather and analyze context information in various situations and environments. However, existing context-aware systems lack the ability to systematically generate and handle various types of context information, and only a few systems have ability learning from environment. In this paper, a general context model is defined to describe various contexts and a context-awareness framework is implemented based in the model, which makes it straightforward to handle and generate various types of context from diverse sensor. The framework is designed to allow a system to sensed, combined, inferred, and learned context information, in order to provide users with services in dynamic environments. We have implemented the proposed framework and applied it to a u-Health management system.

• Korea Information Processing Society Review
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• v.11 no.6
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• pp.56-75
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• 2004

In this article we address some system characteristics and challenging issues in developing Context-aware Middleware for Ubiquitous Computing. The functionalities of a Context-aware Middleware includes gathering context data from hardware/software sensors, reasoning and inferring high-level context data, and disseminating/delivering appropriate context data to interested applications/services. The Middleware should facilitate the query, aggregation, and discovery for the contexts, as well as facilities to specify their privacy policy. Following a formal context model using ontology would enable syntactic and semantic interoperability, and knowledge sharing between different domains. Moddleware should also provide different kinds of context classification mechanical as pluggable modules, including rules written in different types of logic (first order logic, description logic, temporal/spatial logic, fuzzy logic, etc.) as well as machine-learning mechanical (supervised and unsupervised classifiers). Different mechanisms have different power, expressiveness and decidability properties, and system developers can choose the appropriate mechanism that best meets the reasoning requirements of each context. And finally, to promote the context-trigger actions in application level, it is important to provide a uniform and platform-independent interface for applications to express their need for different context data without knowing how that data is acquired. The action could involve adapting to the new environment, notifying the user, communicating with another device to exchange information, or performing any other task.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.15 no.2
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• pp.37-52
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• 2005

Traditional access control models like role-based access control model are insufficient in security needs in ubiquitous computing environment because they take no thought of access control based on user's context or environment condition. In these days, although researches on context-aware access control using user's context or environment conditions based on role-based access control are emerged, they are on the primary stage. We present context definitions md an access control model to provide more flexible and dynamic context-aware access control based on role-based access control. Specially, we describe the conflict problems occurred in the middle of making an access decision. After classifying the conflict problems, we show some resolutions to solve them. In conclusion, we will lay the foundations of the development of security policy and model assuring right user of right object(or resource) and application service through pre-defined context and context classification in ubiquitous computing environments. Beyond the simplicity of access to objects by authorized users, we assure that user can access to the object, resource, or service anywhere and anytime according to right context.

• Journal of Korea Multimedia Society
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• v.7 no.8
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• pp.1017-1024
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• 2004

Ubiquitous system requires intelligent environment and system that perceives context in a proactive manner. This paper describes proactive retrieval method using context patterns in ubiquitous computing. And as the user's contexts change, new information is delivered proactively based on user's context patterns. For proactive retrieval, we extract context patterns based on sequential pattern discovery and association rule in data mining. By storing only information to be needed in near future using the context patterns, we solved the problem of speed and storage capacity of mobile devices in ubiquitous computing. We explain algorithms and an example. Several experiments are performed and the experimental results show that our method has a good information retrieval.

• Journal of Intelligence and Information Systems
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• v.12 no.4
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• pp.61-72
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• 2006

Ubiquitous computing technologies become mature enough to be applied in acceptable ubiquitous services. In particular, in u-shopping area, personalized recommender systems which automatically collect the nomadic user-related context data and then provide them with products or shops in a flexible manner. However, legacy cooperative queries and context-aware queries so far do not come up with dynamically changing situations and ambiguous query commands, respectively. Hence, The purpose of this paper is to propose a personalized context-aware cooperative query that supports a multi-level data abstraction hierarchy and conceptual distance metric among node instances, while considering the user's context data. To show the feasibility of the methodology proposed in this paper, we have implemented a prototype system, CACO, in the area of site search in a large-scale shopping mall.

• Korean Journal of Computational Design and Engineering
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• v.11 no.5
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• pp.365-374
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• 2006

The ubiquitous environment is to support people in their everyday life in an inconspicuous and unobtrusive way. This environment requires information such as the person, his/her preferences, and habits which is available in the ubiquitous system. In this paper, we propose the context aware system that can provide the tailored information service for user in ubiquitous computing environment. Our system architecture is divided into 4 domain models such as context awareness, presentation, interface and inference domain. Each domain model can perform some predefined tasks independently. And we suggest the hybrid algorithm combined with fuzzy and Bayesian method in order to reason what is the suitable information for user. We show the possibility for the real application through applying the system to the TGA (Tour Guide Assistant) for Kyoungju historical site.