Research On Semantic Coordination Model For Open Environment

Information systems evolve into open and dynamic distributed systems. Such systems include multiagent systems, pervasive computing spaces, and (Semantic) Web services. It is clear that coordination plays an important role. Moreover, current interaction models of Web services being incompatible with the REST architectural model of the Web. Therefore, the distributed systems need a middleware for coordination. Especially, in order to ensure truly Web-compliant service communication, there is need for a middleware solution that is based, on persistent information publication, thus allowing services to exchange information in a reference, space and time decoupled manner. The tuple space coordination model is distinguished by its logically shared memory along with data persistence, temporal and spatial decoupling, as well as independence from any computation language or machine architecture–essential properties for coordination in open and dynamic distributed systems.As distributed information systems become more ubiquitous, autonomous, and complex, the need to ground them on common data models grows stronger. Agents in such systems must be able to exchange information, queries, and requests with some assurance that they have a common meaning. One possible approach is to employ Semantic Web technologies for modeling and reasoning about information. Moreover, in conjunction with the idea of the Semantic Web, intelligent inference-based mechanisms shall allow automated discovery, selection, composition, mediation, and execution of Web services.This dissertation presents a Semantic Web Tuplespaces (SWTs) based on a combination of tuple space coordination model and Semantic Web technologies–URI, namespace, RDF, RDF Schema, OWL DL, SWRL. The SWTs can server not only as a repository of semantic information, but also as a middleware to enable communication and coordination based on the principle of publish and retrieve of semantic information in open and dynamic distributed systems. Furthermore, the SWTs can cope with the requirements of security, privacy, and scalability arising in open and dynamic distributed systems. The thesis describes conceptual model of the SWTs and discusses the necessary extensions to the original tuple space. The main efforts of this work are as follows:⑴New types of tuple spaces and tuples are tailored to represent Semantic Web knowledge in languages of RDF, RDF Schema, OWL DL and SWRL.⑵Due to semantics of RDF(S) and OWL DL are not compatible with each other, deciding upon a suitable tuple-based representation: blank nodes and collections.⑶New coordination primitives and a revision of partial Linda-based operations are defined in order to ensure communication and coordination based on the principle of publish and retrieve of semantic information in the form of tuple.⑷New matching mechanisms are provided, which corresponds to different set of coordination primitives. They are①revised version of traditional Linda matching for Semantic Web knowledge,②abstract syntax matching, and③semantic matching.⑸A access control mechanism based on ontology is provided in order to satisfy the security and privacy requirements of open and dynamic distributed systems. The main works are as follows.①An access policy ontology is developed for defining policy rules.②A novel algorithm is developed for reasoning over policy rules.③New tuple spaces, tuples, coordination primitives, and matching are provided for access policy rules.⑹SWTs meta ontology is defined as a formal description of the structure of SWTs. Using the ontology in this context allows a more flexible and efficient management of the tuple space content and the interaction between SWTs and coordination entities, and meets requirement of scalability w.r.t. the open and dynamic distributed systems.⑺An initial version of the SWTs prototype system has been implemented, which is composed of semantic tuplespace, rule tuplespace, and access policy tuplespace. Experimental evaluation demonstrates that the conceptual model is feasible and the prototype system is applicable for real world applications.