Research On Dependability Assurance For Internetware

Active and autonomic software services which are distributed on the nodes of Internetcan collaborate with each other in various manners. It forms a new software paradigmcalled Internetware. Internetware provides an effective means for integration ofheterogeneous resources, and helps people to make full use of the large number ofsoftware services on Internet. And system architecture of Internetware becomesincreasingly complex with the increasing of functional requirements. Therequirements of ensuring trustworthiness have become increasingly prominentbecause that the running environment of Internetware transfers from the traditional"closed, static, controllable" environment to "open, dynamic and decentralized"Internet environment. However, there exist some shortcomings in currentInternetware trustworthiness assurance techniques, such as, the constraint mechanismof trust relationship, accurate recommendation trust information, rational trustinformation attenuation parameters, systematic for trust evolution model, propertrustworthiness assessment, etc. To address the above issues, the thesis has studiedtrustworthiness assurance techniques of Internetware. The main contributions andinnovations are as follows:(1) In aspect of individual entities, the thesis studies trustworthy entity model ofInternetware. A strong trustworthy intelligent Internetware entity model which isintrospective, self-evident and autonomous is proposed. Formal entity dependabilitydescription Language (EDSADL) is defined, so that entities can protect their owntrustworthiness level through introspection mechanism and send announcements forverification. System structure of separating business function modules andtrustworthiness protection module is designed, which ensures the confidentiality ofthe entities’ own business details while giving publicity to their trustworthinessprotection mechanisms to the outside world.“Context-aware--strategy scheduling--behavior trigger "mechanism is designed, so that entities have the ability to perceivestimulation of environment and evolve autonomously. The mechanism ensures that entities can response properly at the time of external environment trustworthinesschanging.(2) In aspect of collaboration among entities, the thesis studies constraint mechanismof trust among Internetware entities. Design by contract ideas are introduced to clearthe rights and obligations of both collaboration sides by “commitment–assessment”mechanism starting from the perspective of service users and providers. It definesconstraints for bilateral specification of collaboration among entities from low-levelinterface semantics to high-level trustworthiness. Description methods ofpre-condition, post-condition and invariant of a trust contract is defined, which ensuretrustworthiness of service users, providers and service interactions. It provides astrong assessment basis for collaboration, cooperation and competition of entities.(3) In aspect of trust transfer parameter, the thesis studies calculation of trust transferattenuation parameters among entities. Process of trust attenuation based onassessment is proposed by integrating advantages of subjective trust and objectiveassessment. Recommendation trust information from entities is integrated throughstep by step calculations and information merging on the basis of trustworthinessassessment of entity environment. Trust transfer attenuation parameter is calculatedby amending the integrated recommendation trust information by use of assessmentsresults of the inter-entity transfer trustworthiness. The method gives full considerationto the impact of external environment and entities conditions to subjective trust value,which makes calculation of trust transfer attenuation parameters among entities moreobjective and accurate.(4) In aspect of the whole system, the thesis studies Internetware trustworthinessevolution model. A formal Internetware architecture modeling method is proposed.An Internetware system structure model is established by structure analysis. AnInternetware trustworthiness evolution model based on hierarchical Petri nets ispresented according to the Internetware system structure model. All kinds of basiccollaboration relationships among entities are modeled in the upper Petri net, whichcomposites the description of the overall system structure and reflects the evolution oftrust relationship among entities. Contract negotiation strategy within entities is modeled in the underlying Petri net. Trust contract negotiation with path guiding isdesigned based on trust level. So that, an Internetware trustworthiness evolutionmodel is established from the perspective of the overall system with combining staticand dynamic, clear structure, and unified description.(5) In aspect of system test and trustworthiness evaluation, the thesis studiesInternetware trustworthiness evaluation model. A trustworthiness evaluation methodwhich suite heterogeneous, structural, dynamic Internetware is proposed. AnInternetware trustworthiness evaluation system is defined, which integrates traditionalstatic metrics and dynamic metrics for Internetware by tree structure. Trustworthinessassessment metrics and its calculation method based on the structural model isproposed, which covers assessment for trustworthiness of Internetware system and itsentities according to description of structual relationship and semantic relationshipamong entities. The model not only is able to evaluate the whole system, but alsohelps users to select optimal entities.