• 제목/요약/키워드: Ontology Schema

검색결과 102건 처리시간 0.022초

RSS와 OLAP 큐브를 이용한 FOAF의 동적 관리 기법 (A Dynamic Management Method for FOAF Using RSS and OLAP cube)

  • 손종수;정인정
    • 지능정보연구
    • /
    • 제17권2호
    • /
    • pp.39-60
    • /
    • 2011
  • 웹 2.0 기술이 소개된 이후 소셜 네트워크 서비스는 미래 정보기술의 기초로서 중요하게 인식되고 있다. 이에, 웹2.0 환경에서 소셜 네트워크를 구축하기 위하여 온톨로지 기반의 사용자 프로필 기술 도구인 FOAF를 활용하기 위한 다양한 연구가 이뤄지고 있다. 그러나 FOAF를 이용하여 소셜 네트워크를 생성 및 관리하는 대부분의 방법은 시간의 흐름에 따라 변화하는 사용자의 소셜 네트워크를 자동적으로 반영하기 어려운 단점이 있으며 다양한 소셜 미디어 서비스가 제공되는 환경에서는 FOAF를 동적으로 관리하기가 쉽지 않다. 따라서 본 논문에서는 기존 FOAF를 이용한 소셜 네트워크 추출방법의 한계를 극복하기 위하여 사용자 프로파일 기술 언어인 FOAF와 웹 저작물 출판 매커니즘인 RSS를 OLAP 시스템에 적용시켜 동적으로 FOAF를 갱신하고 관리하기 위한 방법을 제안한다. 본 논문에서 제안하는 방법은 수집한 FOAF와 RSS 파일들을 스타스키마로 설계된 데이터베이스에 넣어 OLAP 큐브를 생성한다. 그리고 OLAP 연산을 이용하여 사용자의 연결관계를 분석하고 FOAF에 그 결과를 반영한다. 본 논문에서 제안하는 방법은 이기종 분산처리 환경 하에서 데이터의 상호호환성을 보장할 뿐만 아니라 시간의 흐름에 따른 사용자의 관심 및 이슈 등의 변화를 효과적으로 반영한다.

시맨틱 웹 자원의 랭킹을 위한 알고리즘: 클래스중심 접근방법 (A Ranking Algorithm for Semantic Web Resources: A Class-oriented Approach)

  • 노상규;박현정;박진수
    • Asia pacific journal of information systems
    • /
    • 제17권4호
    • /
    • pp.31-59
    • /
    • 2007
  • We frequently use search engines to find relevant information in the Web but still end up with too much information. In order to solve this problem of information overload, ranking algorithms have been applied to various domains. As more information will be available in the future, effectively and efficiently ranking search results will become more critical. In this paper, we propose a ranking algorithm for the Semantic Web resources, specifically RDF resources. Traditionally, the importance of a particular Web page is estimated based on the number of key words found in the page, which is subject to manipulation. In contrast, link analysis methods such as Google's PageRank capitalize on the information which is inherent in the link structure of the Web graph. PageRank considers a certain page highly important if it is referred to by many other pages. The degree of the importance also increases if the importance of the referring pages is high. Kleinberg's algorithm is another link-structure based ranking algorithm for Web pages. Unlike PageRank, Kleinberg's algorithm utilizes two kinds of scores: the authority score and the hub score. If a page has a high authority score, it is an authority on a given topic and many pages refer to it. A page with a high hub score links to many authoritative pages. As mentioned above, the link-structure based ranking method has been playing an essential role in World Wide Web(WWW), and nowadays, many people recognize the effectiveness and efficiency of it. On the other hand, as Resource Description Framework(RDF) data model forms the foundation of the Semantic Web, any information in the Semantic Web can be expressed with RDF graph, making the ranking algorithm for RDF knowledge bases greatly important. The RDF graph consists of nodes and directional links similar to the Web graph. As a result, the link-structure based ranking method seems to be highly applicable to ranking the Semantic Web resources. However, the information space of the Semantic Web is more complex than that of WWW. For instance, WWW can be considered as one huge class, i.e., a collection of Web pages, which has only a recursive property, i.e., a 'refers to' property corresponding to the hyperlinks. However, the Semantic Web encompasses various kinds of classes and properties, and consequently, ranking methods used in WWW should be modified to reflect the complexity of the information space in the Semantic Web. Previous research addressed the ranking problem of query results retrieved from RDF knowledge bases. Mukherjea and Bamba modified Kleinberg's algorithm in order to apply their algorithm to rank the Semantic Web resources. They defined the objectivity score and the subjectivity score of a resource, which correspond to the authority score and the hub score of Kleinberg's, respectively. They concentrated on the diversity of properties and introduced property weights to control the influence of a resource on another resource depending on the characteristic of the property linking the two resources. A node with a high objectivity score becomes the object of many RDF triples, and a node with a high subjectivity score becomes the subject of many RDF triples. They developed several kinds of Semantic Web systems in order to validate their technique and showed some experimental results verifying the applicability of their method to the Semantic Web. Despite their efforts, however, there remained some limitations which they reported in their paper. First, their algorithm is useful only when a Semantic Web system represents most of the knowledge pertaining to a certain domain. In other words, the ratio of links to nodes should be high, or overall resources should be described in detail, to a certain degree for their algorithm to properly work. Second, a Tightly-Knit Community(TKC) effect, the phenomenon that pages which are less important but yet densely connected have higher scores than the ones that are more important but sparsely connected, remains as problematic. Third, a resource may have a high score, not because it is actually important, but simply because it is very common and as a consequence it has many links pointing to it. In this paper, we examine such ranking problems from a novel perspective and propose a new algorithm which can solve the problems under the previous studies. Our proposed method is based on a class-oriented approach. In contrast to the predicate-oriented approach entertained by the previous research, a user, under our approach, determines the weights of a property by comparing its relative significance to the other properties when evaluating the importance of resources in a specific class. This approach stems from the idea that most queries are supposed to find resources belonging to the same class in the Semantic Web, which consists of many heterogeneous classes in RDF Schema. This approach closely reflects the way that people, in the real world, evaluate something, and will turn out to be superior to the predicate-oriented approach for the Semantic Web. Our proposed algorithm can resolve the TKC(Tightly Knit Community) effect, and further can shed lights on other limitations posed by the previous research. In addition, we propose two ways to incorporate data-type properties which have not been employed even in the case when they have some significance on the resource importance. We designed an experiment to show the effectiveness of our proposed algorithm and the validity of ranking results, which was not tried ever in previous research. We also conducted a comprehensive mathematical analysis, which was overlooked in previous research. The mathematical analysis enabled us to simplify the calculation procedure. Finally, we summarize our experimental results and discuss further research issues.