| A workflow is the automation of procedures where documents, information or tasks are passed between participators according to a defined set of rules to achieve, or contribute to, an overall business goal.The mobile agent computing is a new distributed computing paradigm. A mobile agent is an intelligent entity that can carry the task specification, migrate between sites, and utilize local resources to execute one or more tasks. Since the mobile agent computing has many advantages, such as cutting down network overload and supporting unstable computing environment, it is becoming a hot topic in the distributed computing paradigm research.The migrating workflow management is an emerging technology that applies the mobile-agent computing paradigm to workflow management. According to the framework of the migrating workflow management system proposed by professor ZENG, there are three core elements in a migrating workflow management system: migrating instance, workplace and migrating workflow engine. A migrating instance is the business process executor, which is constructed from a defined mobile agent stereotype. The migrating instances cooperate with one another to accomplish a business process. Workplaces are delegates of the workflow participators, such as an enterprise or organization. A workplace is composed of an anchorage server and its connected workstation network. Migrating instances run on the anchorage server, and the workstations provide actual workflow services for migrating instances. The workflow services may include computing service, data service, human computer interaction service, and so on. The migrating workflow engine is responsible for workflow process definition, workplace organization, the creation of migrating instances and workflow monitoring. Generally speaking, it is the function of the enterprise or organization that triggers the workflow process to manage the migrating workflow. Different from the traditional workflow model, the migrating workflow is a process in which one or more migrating instances migrate continuously and utilize local workflow service to execute their tasks. The workplace layout is one of two key issues in the migrating workflow research. This thesis defines a concept of workflow domain, which is the sum of all workplaces that fulfills the requirements of a given business process. If a workflow domain is configured and fixed before the workflow startup, and the workflow membership does not change during workflow execution, it is named as a static organization workflow domain. If the workflow domain membership can be changed during workflow execution, it is called dynamic organization workflow domain.The other key issue in the migrating workflow research is how to keep the workplaces to offer efficient services in a well-ordered manner. This is called the migrating instance scheduling mechanism. The migrating workflow is a parallel computing model. It not only permits multiple migrating instances to execute on the same business process, but also does it allow an enterprise or organization to take part in multiple business processes. Each business process is executed by its set of migrating instances. As a result, multiple migrating instances may arrive at the same workplace at a time, which can cause two or more migrating instances to contest for the resources from a workplace. Anarchism in resource competition not only tampers with the workplace stability, but also results in abnormal execution of the migrating workflow system.This study is mainly supported by the National Natural Science Foundation of China under Grant No.60473123, based on the migrating workflow framework proposed by professor ZENG This thesis absorbs the research results of relevant fields, focuses on the implementation method of the workflow domain organization model and the scheduling mechanism of migrating instances in workplaces. The study has also built a prototype system to validate the conclusions. The main contributions of this thesis are described as follows:1. The static organization model of the workflow domains and its implementation. The static organization model implementation can be abstracted as the workflow task allocation mechanism through coalition formation. Once a workflow coalition is formed, the workflow creator can not only determine the set of workplaces on which a migrating instance may login, but also map out the travel schemes for those migrating instances based on the business process logical and workflow services provided by individual coalition members. The author has focused on a task-allocation based ability-confidence coalition, where the ability confidence is defined as the level of belief that a workflow creator trusts each coalition member on providing particular services. If an enterprise or organization believes itself have the ability to provide one or more services for certain business process, it can contest some role of the workflow domain. If the workflow creator believes a competitor is competent for a service task, it enlists such a competitor as members of workflow domain. Our research assumes that all enterprises or organizations are rational, and the contest is cooperative. Chapter 2 presents the service ability confidence definition and its calculation, and then develops a task allocation algorithm based on the ability confidence, which is validated in the environment of Collaborative Product Commerce.2. The dynamic organization model of workflow domains and its implementation. For some unstructured business process such as an ad-hoc workflow, it is impractical or unnecessary to define a complete business process description or construct a whole workflow domain for the business process. In contrast to the static model implementation, the dynamic model can be abstracted as a goal-oriented travel layout problem. The author has studied a workplace-navigation based travel layout method, where the navigation indicates travel suggestions for migrating instances provided by a workplace per its service ability comprehension of the workflow domain participators including it self. Following the navigation suggestions, a migrating instance can, without changing it goal, amend its work plan and choose its workplaces. Chapter 3 defines the concept of a navigation thread, creates the migrating workflow navigation model, and then develops a navigation-based migrating instance task execution algorithm. Chapter 2 also validates this research in the environment of Collaborative Product Commerce.3. The migrating instance scheduling mechanism within a workplace. A workplace is the integration of an anchorage server and its connected workstation network, where the anchorage server is the place for migrating instance execution, and the workstation is a workflow service executor. The workplace, as a delegate of the enterprise or organization attending the workflow, provides workflow services for one or more tasks in the business process. When more than one migrating instances login the same workplace, there may be resource contests. The migrating instance scheduling mechanism can be abstracted as a workflow service decision-making problem. This thesis emphasizes on a migrating instance queuing mechanism and workstation preferential choice mechanism. The queuing mechanism helps maintain the stabilization and reliability when many migrating instances utilize the same workflow service on the same workplace. And, the workstation preferential choice mechanism is used to choose the best suitable workstation when many workstations can provide the same workflow service. Chapter 4 first constructs the sole-work-node queuing model and the compound-work-node queuing model, proposes the implementation methods of these models, and then designs a workstation preferential choice algorithm. And finally, the above research is validated in the environment of Collaborative Product Commerce.4. The monitoring and management of migrating instances. In the migrating workflow system, the migrating instance is the mobile computing entity, which may lie in different physical places at different times. So the key issue of migrating instance monitoring and management is how to trace migrating instances. This thesis mainly studies a migrating instance tracing method based on GSM network principles, and designs a running log management policy that combines the dynamic transient storage and persistent storage. Chapter 5 defines the concept of migrating position trace, designs the migrating instance trace method and its log storage policy, and further discusses the procedures of log storage, search and validation.The main innovative contributions of this thesis are:1. The thesis proposes a task allocation method based on ability confidence coalition. This method takes attending enterprises or organizations as rational agents, maps the workflow domain static organization problem into a coalition-based multi-agent task allocation problem. The ability confidence is deduced from ECA role sets of business operation and agent service ability. If a rational agent believes it is capable to provide service for operation A, we say this agent is self-confident with operation A. If a rational agent X believes rational agent Y is capable to provide service for operation A, we say agent X trusts agent Y. We measure both self-confidence and trust as confidence. Because both the self-confidence and trust are mental elements of an action selection agent, compared with profit coalition based task allocation methods, such as the collaborative gaming, that sets absolute abilities to agents, the task allocation method based on ability confidence coalition not only provides a finer actor ability description, but also opens out the intelligence attribute of actors solving problem based on its ability.2. This thesis proposes a workplace-navigation based migrating workflow execution method. This method assumes that each migrating instance has its specific workflow goal, but it is lack of the whole business process description and migration route, so it needs navigation suggestions (a.k.a. navigation thread) provided by workplaces to layout tasks dynamically and help accomplish migration. A navigation thread is the workplace's local knowledge about business processes. The navigation thread is described as a directional graph G=(V, E), with each vertex denotes a service, and each edge denotes the sequential relationship between two services. Note that, each service is corresponding to a concrete task and a workplace in which migrating instance use this service to execute the task. Compared with the traditional approach to improve workflow flexibility through workflow modeling optimization, our proposed navigation mechanism utilizes the workflow knowledge distributed in all workplaces to maximize the flexibility of migrating instance executing tasks. This multi-knowledge source navigation system enables migrating instances to start the workflow under the status of incomplete business process description, which makes it very easy to deal with workflow exception. What's more, this navigation system also makes the workflow flexibility no longer absolutely relying on the foregoing knowledge of workflow designers, thus this method is very suitable to non-structural and inter-organizational workflow management.3. This thesis proposes the queuing-theory based migrating instance service collision resolution method. Considering that a workplace is physically composed of an anchorage server and its connected workstation network, the service collision resolution method establishes the queuing models for sole-work-nodes and compound-work-nodes respectively. Taking into account the time at which a migrating instance arrives at the workplace and the service time, these queuing models schedule migrating instances through a dynamic preferential queue according to service rules. The sole-work-node queuing indicates that migrating instances queue up at workplaces, and the compound-work-node queuing indicates that an anchorage server dispatches migrating instances to queue up at workstations. Although the queuing is a simple idea, it is rarely used in the mobile computing research. However, it is very important to the workflow management because resource contests may cause instability of work nodes, migrating instance abortion, or even the whole workflow failure.Since the migrating workflow is an emerging workflow research field, it is far from mature in both theory and applications. To further the study started in this thesis, the author proposes the following future works:1. The multi-goal decision-making based workflow static organization method. When all self-confidence, trust, and profit are considered at the same time in terms of coalition, the task allocation problem becomes a multi-goal decision-making problem. How to implement the workflow domain static organization model based on multi-goal decision-making, will be one of the topics justified for in-depth discussions.2. The navigation thread semantics and its judgment. The quality of the navigation thread directly dictates the reliability of a migrating workflow system and the validity of the navigation-based migrating workflow execution method. How to describe, distinguish, and evaluate the navigation thread at the higher level of semantics will be another future tasks to fulfill.Based on aforementioned work, research areas such as migrating workflow transaction attribution, multi migrating instance cooperation and semantics-based service detection and combination, should also be explored.
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