Byung-Gon Kim

The index organizations for RDF and RDF schema

In semantic Web, metadata and ontology for representing semantics and conceptual relationships of information resources are essential factors. RDF and RDF schema are the W3C standard models for describing metadata and ontology. Therefore, storing and querying RDF and RDF schema is one of major tasks in applications on the semantic Web. Many existing studies are mainly tailored to RDF triple statements without considering RDF schema. And most studies are focused on querying over simple triple statements and pass over various query forms such as keyword-based query and path-based query. In this paper, we propose two indexing techniques considering both RDF and RDF schema. First, we present a path index for processing structure-based query of RDF and RDF schema. Path index stores all path information in graph models of RDF and RDF schema and supports hierarchical relationships between classes or properties. Second, we describe a keyword index for processing keyword-based query. Keyword index stores all resources that contain indirectly or directly a certain keyword in RDF. So, if users keyword is given, all resources that contain a corresponding keyword can be retrieved easily

Design of Storage Structure for Path-Based Query on RDF and RDF Schema

In the Semantic Web, metadata and ontology for representing semantics and conceptual relationships of information resources are essential factors. RDF and RDF Schema are the W3C standard models for describing metadata and ontology. In this paper, we focus on a result of analyzing available query patterns considering both RDF and RDF Schema. And we propose a structure to store and query using path information in graph models of RDF and RDF Schema. The proposed structure supports whole query patterns fairly. We can retrieve entities that are reached from a certain class, property, resource, or literal in RDF and RDF Schema without a loss of performance because of multiple joins with tables. And, through encoding schemes, we determine easily hierarchical relationships between classes or properties.

A filtering method for k-nearest neighbor query processing in multimedia data retrieval applications

Efficient query processing in multi-dimensional indexing structures is an important issue for effective employment of multimedia data applications. A considerable number of studies, to date, have been conducted in this area. However the efficiency of the proposed solutions generally deteriorates as the dimension of the data increases. We introduce a filtering method for efficient processing of k-nearest neighbor queries in multi-dimensional indexing structures. The proposed method is based on the R*-tree, and uses a vantage point for effective similarity searches. Through the use of a vantage point we are abler to filter out data objects and decrease the distance computation time. Experimental results show that the k-nearest neighbor search that uses the proposed method consistently outperforms the search performance that uses the existing method for the R*-tree.

Management System for OWL Documents in Distributed Environment on the Semantic Web

In the current Web, it is not possible to manage information resources manually and intelligently. And most users prefer more accurate information. To overcome these limitations of the current Web, the semantic Web was conceived. Unlike the current Web, in the semantic Web, metadata and ontology play important roles for advanced information retrieval systems. For describing semantics and reasoning about information resources on the Web, RDF, RDF Schema and OWL are proposed by W3C. OWL has rich expressive power and is considered as the next standard language for describing metadata and ontology. The related information resources are placed in distributed systems on the Web. So, for providing seamless services without the awareness of far distance, efficient management of the distributed information resources is required. And to be provided with richer query results, people need to acquire related information through integrating the distributed ontologies. Among languages for describing metadata and ontology, only OWL can support dispersibility of Web. In this paper, first we classify features of OWL for supporting distributed environment on the Web and propose strategies for united query processing of the distributed ontologies. Secondly, we suggest methods of storing ontologies according to the proposed strategies. Finally, we propose an indexing method to improve query answering performance.

Storage structure and management skills for RDF schema versioning in RDB environment

With the growing use of Internet information exchange, interest about semantic Web is rising for satisfying the users various requests. Ontology is a basic building concept for semantic Web and ontology language such as RDF/RDF schema is a basic tool for constructing ontology system. One of the major points when constructing ontology with RDF/RDF schema is versioning because ontology knowledge is not static but change as times go by. Therefore, ontology systems should provide versioning skills which reflect changes in domain, changes of data concept, and changes of relations between data resources. This paper discusses the problems of RDF schema versioning and provide storage structure and management skills for RDF schema versioning in RDB environment. We introduce version graph and transitivity rule which is used for version selection for some data. Finally, we introduce a storage structure for implementing the versioning scheme