JuHum Kwon

Visual modeling and formal specification of constraints of RBAC using semantic web technology

The role-based access control (RBAC) model has garnered great interest in the security community due to the flexible and secure nature of its applicability to the complex and sophisticated information system. One import aspect of RBAC is the enforcing of security policy, called constraint, which controls the behavior of components in RBAC. Much research has been conducted to specify constraints. However, more work is needed on the aspect of sharing information resources for providing better interoperability in the widely dispersed ubiquitous information system environment. This paper provides visual modeling of RBAC policy and specifies constraints of RBAC by employing a semantic web ontology language (OWL) to enhance understanding of constraints for machines and people in a ubiquitous computing environment. Using OWL, constraints were precisely formalized according to the constraint patterns and the effectiveness of OWL specification was demonstrated by showing the reasoning process.

Intelligent semantic concept mapping for semantic query rewriting/optimization in ontology-based information integration system

Recently, ontology has been recognized as one of the most suitable global conceptual models for information integration architecture due to its easy taxonomical classification of data model and plentiful support of integrity constraint. However, the concept of mapping from global ontology to local information systems depends mostly on the simple metadata structures that allow for the mapping elements to be extracted with an If-Then-Else comparison statement. This kind of mapping is not suitable for ontology based data model in which the concepts are in the multiple subsumption relations. That is, there needs to be a semantic concept mapping in the case of a global concept that is to be mapped to the most specialized/generalized local concept in multiple Is-A structure, which cannot be mapped with simple direct one to one mapping. This kind of mapping needs inference mechanism to map one concept to substantially many target concepts in the concept inclusion hierarchy for an effective semantic query rewriting/optimization. In this paper, we provide an innovative method for semantic ontology concept mapping using Metadata-Based Logic (MBL) approach, which is equipped with knowledge inference mechanism so that the mapping elements can be reasoned automatically. We present semantic mapping patterns to accommodate subsumption problem and detect incoherence for a given global query. The experimental results gave viable results on the semantic query rewriting/optimization.

Deriving similarity for Semantic Web using similarity graph

One important research challenge of current Semantic Web is resolving the interoperability issue across ontologies. The issue is directly related to identifying semantics of resources residing in different domain ontologies. That is, the semantics of a concept in an ontology differs from others according to the modeling style and intuition of the knowledge expert even though they are the same forms of a concept in each respective ontology. In this paper, we propose a similarity measure to resolve the interoperability issue by using a similarity graph. The strong point of this paper is that we provide a precise mapping technique and similarity properties to derive the similarity. The novel contribution of this paper is that we provide a core technique of computing similarity across ontologies of Semantic Web.

The conflict detection between permission assignment constraints in role-based access control

Assuring integrity of permission assignment (PA) constraints is a difficult task in role-based access control (RBAC) because of the large number of constraints, users, roles and permissions in a large enterprise environment. We provide solutions to this problem using the conflict concept. This paper introduces the conflict model in order to understand the conflicts easily and to detect conflicts effectively. The conflict model is classified as a permission-permission model and a role-permission model. This paper defines two type conflicts using the conflict model. The first type is an inter-PA-constraints (IPAC) conflict that takes place between PA constraints. The other type is a PA–PAC conflict that takes place between a PA and a PA constraint (PAC). Also, the conditions of conflict occurrence are formally specified and proved. We can assure integrity on permission assignment by checking conflicts before PA and PA constraints are applied.

Bridging real world semantics to model world semantics for taxonomy based knowledge representation system

As a mean to map ontology concepts, a similarity technique is employed. Especially a context dependent concept mapping is tackled, which needs contextual information from knowledge taxonomy. Context-based semantic similarity differs from the real world similarity in that it requires contextual information to calculate similarity. The notion of semantic coupling is introduced to derive similarity for a taxonomy-based system. The semantic coupling shows the degree of semantic cohesiveness for a group of concepts toward a given context. In order to calculate the semantic coupling effectively, the edge counting methods is revisited for measuring basic semantic similarity by considering the weighting attributes from where they affect an edge’s strength. The attributes of scaling depth effect, semantic relation type, and virtual connection for the edge counting are considered. Furthermore, how the proposed edge counting method could be well adapted for calculating context-based similarity is showed. Through experimental results are provided for both edge counting and context-based similarity. The results of proposed edge counting were encouraging compared with other combined approaches, and the context-based similarity also showed understandable results. The novel contributions of this paper come from two aspects. First, the similarity is increased to the viable level for edge counting. Second, a mechanism is proviede to derive a context-based similarity in taxonomy-based system, which has emerged as a hot issue in the literature such as Semantic Web, MDR, and other ontology-mapping environments.

RGSN model for database integration

Considering information integration, we have a careful look at many types of collisions based on heterogeneities. We propose a relational global semantic network (RGSN) to solve this problem This is based on the WordNet which defines the relationships among words. The main structure of RGSN is to derive connections among entities in each schema and finally provide a foundation to solve the heterogeneity. We suggest an implementation of SELECT query that can be used in the environment of the integrated heterogeneous databases. It helps users derive data correctly without considering the various schema structures of many local databases. That is prerequisite for the utilization of integrated databases and would be the main contribution of this paper.