JOURNAL OF INFORMATION SCIENCE AND ENGINEERING 31, 415-432 (2015) 415 Ontology Kernel  A Convolution Kernel for Ontology Alignment * JEONG-WOO SON § , HEE-GUEN YOON ‡ AND SEONG-BAE PARK ‡,+ § Broadcasting and Telecommunications Media Research Laboratory Electronics and Telecommunications Research Institute Daejeon, 305-700 Korea E-mail: jwson@etri.re.kr ‡ School of Computer Science and Engineering Kyungpook National University Daegu, 702-701 Korea E-mail: {hkyoon; sbpark}@sejong.knu.ac.kr Every ontology entity such as a concept or a property has its own structural infor- mation represented as a graph due to the relations with other entities. Therefore, it is im- portant to consider not only its lexical similarity but also structural similarity in ontology alignment. This paper proposes ontology kernel that computes both types of similarities simultaneously. The idea of this kernel is to measure the structural similarity of ontology entities by mapping their entity graphs into the space spanned by entity random walks. The graph of an entity in the kernel expresses all relations with other entities. Thus, the ontology kernel can compare the similarity between entities no matter how complex the entities are and no matter how many kinds of relations they possess. A series of experi- ments with the standard data sets prove the generality and the superiority of the ontology kernel in ontology alignment. Keywords: ontology alignment, ontology kernel, convolution kernel, graph similarity, hyper graph 1. INTRODUCTION Ontology is an explicit, machine-readable specification of a shared conceptualiza- tion of a domain. It can be an information source for various applications. Especially in Semantic Web, an ontology is essential not only as an information source but also for supporting inter-operability among applications. One of the issues related with ontolo- gies is that most ontologies are written separately and independently by human experts to serve particular tasks or application domains. Thus, there are many ontologies even in a single domain, and it causes semantic heterogeneity. This heterogeneity of ontologies for a domain becomes an obstacle for inter-operability of applications. Therefore, a method to merge the related ontologies is required to restore the inter-operability. Ontology alignment aims to merge two ontologies which contain similar semantic information by identifying semantic similarities between entities in the ontologies. Thus, Received August 19, 2013; revised December 18, 2013 & February 13, 2014; accepted March 17, 2014. Communicated by Chang-Shing Lee. * This work was supported by the ICT R&D program of MSIP/IITP, Rep. of Korea (14-000-11-002, Develop- ment of Object-based Knowledge Convergence Service Platform using Image Recognition in Broadcasting Contents and the Industrial Strategic Technology Development Program (10035348, Development of a Cog- nitive Planning and Learning Model for Mobile Platforms) funded by the Ministry of Knowledge Economy (MKE, Korea). + Corresponding author.