Dongwon Jeong

Context-Aware access control mechanism for ubiquitous applications

With a rapid development of ubiquitous computing technology in the home and community, users can access information anytime and anywhere via personal devices such as PDA and internet mobile phone. Similarly, more flexible access control is required in the ubiquitous applications. In this paper, we propose a context-aware access control mechanism, which dynamically grants and adapts permissions to users according to the current context. We extend the role-based access control(RBAC) model to deal with the context information in ubiquitous environment. Unlike the traditional RBAC, the proposed access control mechanism can consider context information such as location, time and system resources by the context-aware agent and state checking matrix(SCM).

SPARQL graph pattern rewriting for OWL-DL inference queries

This paper focuses on the issue of OWL-DL ontology queries implemented in SPARQL. Currently, ontology repositories construct inference ontology models, and match SPARQL queries to the models, to derive inference results. Because an inference model uses much more storage space than the original model, and cannot be reused as inference requirements vary, this method is not suitable for large-scale deployment. To solve this problem, this paper proposes a novel method that passes rewritten SPARQL queries to the original ontology model, to retrieve inference results. We define OWL-DL inference rules and apply them to rewriting Graph Patterns in queries. The paper classifies the inference rules and discusses how these rules affect query rewriting. To illustrate the advantages of our proposal, we present a prototype system based on Jena, and address query optimization, to eliminate the disadvantages of augmented query sentences. We perform a set of query tests and compare the results with related works. The results show that the proposed method results in significantly improved query efficiency, without compromising completeness or soundness.

Persistent storage system for efficient management of OWL web ontology

This paper proposes a new persistent storage to efficiently manage OWL Web ontologies. The Semantic Web is recognized as a next direction for progress of the current Web. To realize the Semantic Web, various technologies have been developed. Especially, OWL (Web Ontology Language) is the most important and state-of-the-art technology toward the ideal Semantic Web. However, most of research is being focused on designing and building OWL documents (OWL Ontology). One of the most important issues is how to efficiently and persistently store a very large OWL data into database management systems. In this paper, we propose a persistent storage system to achieve the purpose. This paper describes the performance evaluation result on the load time. The experiment result explicitly shows that our proposal provides more enhanced performance comparing with the existing systems.

A message conversion system, XML-based metadata semantics description language and metadata repository

Metadata can be used to precisely represent data semantics. It can also serve to improve data sharing and exchange. Because the various types of metadata are created in different ways, they can suffer from a problem of inconsistency. Recently, metadata gateway methods have been researched to solve this problem. However, the performance of the existing approaches based on metadata schemas is poor and their maintenance (adaptation of metadata changes) is time consuming. In this paper, a novel message conversion system is proposed, which functions by separating the heterogeneous mapping information from the mapping rules of the metadata, in order to overcome the drawbacks of the existing metadata gateway methods. The proposed system controls the standardized data elements dynamically based on the Metadata Registry (MDR), which is one of the most important elements of the ISO/IEC 11179 standard. The problems associated with adding supplementary metadata are resolved, since the standard provides for incorporating additional data elements created in the future. MSDL is defined as a protocol which can be used for exchanging messages between heterogeneous systems, and which ensures that all of the systems have their own independent metadata schemas.

SPARQL Graph Pattern Rewriting for OWL-DL Inference Query

Graph pattern is the key body of a SPARQL query. Prevalent SPARQL query treatment delivers queries to OWL ontology model directly. To obtain inference results, the graph pattern are matched with inference ontology model which is generated by ontology inference engine. Since an inference model occupies much larger space than original model, and can not be reused as inference requirement varies, this method is not suitable to wide deployment in large scale. Alternatively, this paper proposes a novel method which sends rewritten graph patterns to original ontology model to acquire inference results. This method features in the reuse of original model between users, and avoidance of the heavy workload caused by generating and storing ontology inference model. The paper defines the ontology inference rules which affect the query resolving, and addresses a detailed process for rewriting graph pattern based on these rules. A prototype system is implemented to compare our proposal with current approaches. The experiment results show our methodpsilas advantages in aspects of completeness, soundness and effectiveness.

UbiMDR: Supporting Application-Independent Semantic Interoperability for Ubiquitous Applications

This paper proposes UbiMDR, a MDR (Metadata Registry)-based framework for supporting semantic consistency in ubiquitous computing environments. The chief objective of the UbiMDR is to let ubiquitous applications consistently and independently use information of sensors in a variety of sensor fields. Currently, applications depend on their sensor field. In other word, an application can utilize just information from a specific sensor field. To overcome this restriction, many issues from a hardware or software view must be resolved. This paper focuses on the consistent semantic management to provide the semantic interoperability between ubiquitous applications under ubiquitous environment consisting of various and different sensor fields. The UbiMDR provides infrastructure support for semantic consistency, sensor field-independent information utilization, and context-rich application development.

A comprehensive study on handover performance of hierarchical mobile IPv6

Recently, IETF has standardized Mobile IPv6 (MIPv6) and Hierarchical Mobile IPv6 (HMIPv6) for supporting IPv6 mobility. Even though existing literatures have asserted that HMIPv6 generally improves MIPv6 in terms of handover speed, they do not carefully consider the details of the whole handover procedures. In this paper, based on the current IETF standards of both MIPv6 and HMIPv6, we conduct a comprehensive study of all IP-level handover procedures. We also provide a mathematical analysis on MIPv6 and HMIPv6 performance in terms of handover speed, and reveal that the average HMIPv6 handover latency is not always lower than the average MIPv6 handover latency. A vital finding of our analysis is that some optimization techniques for movement detection and duplicate address detection are essential to increasing the benefit of HMIPv6

An algorithm for automatic inference of referential integrities during translation from relational database to XML schema

XML is rapidly becoming one of the most widely adopted technologies for information exchange and representation on the World Wide Web. However, the large part of data is still stored in a relational database and we need to convert those relational data into an XML document. There are existing approaches such as NeT and CoT to convert relational models to XML models but those approaches only consider explicit referential integrities. In this paper, we suggest an algorithm to reflect implicit referential integrities to the conversion. The proposed algorithm provides several good points such as improving semantic information extraction and conversion, securing sufficient referential integrity of the target databases, and so on.

An Efficient Web Ontology Storage Considering Hierarchical Knowledge for Jena-based Applications

Abstract: As well as providing various APIs for the development of inference engines and storage models, Jena is widely used in the development of systems or tools related with Web ontology management. However, Jena still has several problems with regard to the development of real applications, one of the most important being that its query processing performance is unacceptable. This paper proposes a storage model to improve the query processing performance of the original Jena storage. The proposed storage model semantically classifies OWL elements, and stores an ontology in separately classified tables according to the classification. In particular, the hierarchical knowledge is managed, which can make the processing performance of inferable queries enhanced and stores information. It enhances the query processing performance by using hierarchical knowledge. For this paper an experimental evaluation was conducted, the results of which showed that the proposed storage model provides a improved performance compared with Jena.

SS-RBAC: Secure Query Processing Model for Semantic Sensor Networks

This paper proposes a novel secure query processing model for semantic sensor networks. A semantic sensor network (SSN) is a sensor network which includes semantics of sensory data and context information, and relationships between the semantics. In brief, SSN is an extension of the current sensor network (SN) and realized by using semantic Web (SW) technologies. Although various researches have been activated on SSN, there is little activity on how to access data in semantic sensor networks in safe. This paper proposes a new access control model for secure query processing under semantic sensor networks. The proposed security model is based on RBAC (role-based access control) and enables secure access control of ontology for SSNs.