Study On Formalization Of Ontology Evolution With Pi Calculus

With the explosive growth of Internet information, ontology has increasingly been growing into an important network information carrier and representation format. Ontology was originally a philosophical concept, referring to the nature of existence and reality. In today's Information Era and the rapid development of Internet technology, ontology as one of the core concepts of Web 2.0, comes to refer the conceptualization of knowledge in specific domains. With in-depth study of ontology engineering, ontology related topics have aroused an important interest of computer knowledge representation such as in bioinformatics, genetic engineering, aerospace technology, and a wide range of applications in modern industry.Substantial increase in the management of the ontology brings many new challenges. Among them, the ontology evolution is an important area of research in ontology management of ontology engineering. The changes in the domain knowledge, the understanding of the conceptual model and the changes in the representation may lead to ontology evolution. With deeper understanding of the domain, there might be a variety of crossing and integration between different ontology. The size and structural complexity of the ontology with such in-depth, cross-cutting and integration make the ontology more difficult to maintain and manage. Thus, ontology evolution could be unavoidable and more and more urgent.Ontology evolution can be roughly divided into six phases, namely, discovery of the change, the representation of the change, the semantic change, implementation of the change, spread of the change and confirmation of the change. The discovery of the change is the motivation of ontology evolution, and the implementation of the change fulfills the ontology evolution. Among these, the representation of the change is the core and basis of all the phases in an ontology evolution procedure. This article focuses on such representation of the changes.Pi calculus is a process concurrent calculus, which is a convenient mechanism in describing the concurrent information exchange in a formal system. Through the processes and channels, Pi calculus may be used to describe the interaction and communication among various components of system. The communication mechanism is used to describe the information exchange between processes. The processes might transfer the names of the channels, pass the name of as the appropriate message, and match those names to determine whether the contents of the message are in line with expectations, and then continue with the further concurrent or select processes. Ontology evolution has the nature of the concurrent execution, by understanding the full dynamic semantics of the evolution, we find that the needs of ontology evolution involves the exchange of information between internal entities. That is the reason this paper selects Pi calculus as a tool as the representation mechanism of ontology evolution.This work focused on the following areas:1) The establishment of an ontology meta-model. In this paper, we made a thorough analysis of the different structure of ontology and come to the common elementary structure of ontology. Compare the existing meta-model system, the proposed ontology element model consists of a new entity type: individual of property, in order to describe the relationship exists between the specific classes and individuals. The benefit of this model lies to distinguish the conceptual definitions of properties and the examples of individual properties (ordered pair of class individuals), which makes it easier to manage the various entities of an ontology. In addition, the analysis of this basic ontology evolution disclosed the elementary changes corresponding to the structural changes. This prepares for the formal description of ontology evolution and the evolution of the dynamic semantics.2) A Pi Calculus based formalization of ontology evolution. Based on the meta-model of ontology with the various entities, we built a Pi calculus-based formalization of the structural changes in ontology evolution. Four distinct states (initial, waiting, running, dying) were identified and formalized as different processes. This clarifies the various roles of entities of the meta-model in the dynamic evolutional environment. With the in-depth understanding of the semantics of the duplication operator, we defined the process of the initial state. The names of the channels are explored to formalize the entity names of the ontology. This avoids the short of Pi calculus that new process cannot be created afterwards the establishment of the system. Meanwhile, the entity name is described as a channel name, which might be passed in the channel as a message. It prepares the method to formalize the dynamic semantics of the ontology evolution with the information communication of the processes.3) Clarification of the semantics of structural changes. Through the process of communication under the framework of Pi calculus, the semantics of structural changes on the ontology entities was formally described. So as to achieve the dynamic semantics the evolution, we applied the dynamic information delivery mechanism of Pi calculus to ensure the consistency of structural changes in the evolution.4) Feasibility demonstration with specific examples. Through the examples of adding and deleting a class, we showed the applicability of our formal method of the Pi calculus based representation of changes in ontology evolution.