An Ontology Model Based On SetPi-calculus

Ontology defines the representation and description of the field knowledge in semantic web. It is a shared model of conceptual formal specification. Ontology extracts abstract concepts in the objective world, and definitions relevant connections between concepts and constraints, with the precise mathematical way to make ontology computer-readable. Ontology is the basis of communication language among different entities and consensus of domain knowledge definition, which reflects the common recognition related to the field of concept set. It defines the fields of knowledge and their relationship to achieve knowledge integration, sharing and reuse.But with the massive growth in network data, knowledge and understanding constantly updating, the field of self-generated change expansion, domain ontology is also needed to be adjusted accordingly. Thus, there derived the ontology evolution. Ontology evolution is based on changes that caused adaptive changes by the problems of ontology consistency. Ontology evolution process is generally divided into six phases respectively, that is change capture, change representation, change semantic, change propagation, change implementation and change confirmation. Ontology evolution will lead to the definition of data with unknown term or different interpretations, giving rise to ontology versions incompatible. Because ontology evolution is a complex and trivial process, the various changes will lead to a variety of other related changes, therefore, ontology evolution can not be done manually, but to design the appropriate system to protect the evolution for a variety of inconsistent problems. But the ontology may be reused and depends on the other ontologys, with the increment of dependent ontology, the complexity of ontology evolution is higher. In addition, the ontology evolution can also occur in the distribution systems, so tracking the changes of each ontology and establishing an efficient management system is facing great difficulties.Users'requirement and feedback will lead to ontology modifications, and will cause ontology changes. To design and implementation of ontology management system, to address change and ensure the accuracy of ontology maintenance, first of all need to describe changes with an appropriate format, that is changes require a formal model. However, the existing ontology languages such as OWL, etc., most of all are based on logic, for the formal representation of ontology change, OWL, DL, or other languages can only capture the static semantics, but can not capture the dynamic changes, even if the ontology consistency check can be used with logic implementation, the initial change in the dynamic sense, especially information on the interaction between different entities will be difficult to capture.To find a reasonable modeling tool for ontology evolution, this paper is focused on the process algebra Pi-calculus. Pi-calculus is presented by Robin Milner which is based on CCS mobile processes, that is composed of processes and names. Because Pi-calculus allows the channel to pass the names, so it can depict dynamic topology systems and has the ability to describe the system physical mobility vividly. However, we find Pi-calculus can not add a physical description of the relationship between entities, which become the bottleneck of the modeling study. In order to achieve the ontology evolution modeling, this paper adopted a method of expansion with Pi-calculus.First, based on the concept "collection", this paper expands the syntax of Pi-calculus, adding four operators to realize the function of connection between entities, and named new calculus SetPi-calculus. Then, analysing the expansion of the four operators, presenting five reduction rules, four congruence rules, and define bound names and free names of the four operators.Secondly, shows how to add relationships between entities with a use case, and implement the SetPi-calculus theory in the field of mobile Ad Hoc networks. Experiment shows that SetPi-calculus not only retains Pi-calculus for concurrent systems and describes the ability of mobile systems, but also has the ability to add connections between entities.What's more, this paper will applied SetPi-calculus theory to the modeling of ontology evolution process, representing domain, range, concepts, attributes and instances in a formal way, and mapping ontology entities to SetPi-calculus. In addition, this paper use SetPi-calculus to characterize the evolution process including adding entity, removing entities, entity relationships transfer and establishment of relations between entities as elementary changes. Then, model complex changes and complicated changes by combination with variety of elementary changes, to achieve a complete model of evolution process.Finally, this paper analyzes the consistency of ontology evolution process model, gives various methods for deciding consistency and relevant proof. Experiment shows that this ontology evolution model can saves unnecessary analysis of evolution consistency and improves its efficiency.