Study On Dynamic Adaptability In The Migrating Workflow System

The migrating workflow is an emerging technology that applies the mobile computing paradigm to workflow management. 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. In the migrating workflow system, workplace is the running location of migrating instances. It provides safe running environment and workflow services for migrating instances on behalf of the workflow participants. Workflow services are not only the data resources of the participants but also their business activity or business sub-process. A migrating instance is the business process executor, which is modeled from a defined mobile agent prototype. It not only executes well-defined structured business process, but also deals with incomplete workflow explanation. The workflow explanation need not plan all the activities, transfer relations and describe all the accessible workplace, place services, service rules and service steps for migrating instances. Incomplete workflow explanation may be partly defined based on the original information of business process, and be extended by the service finding, migrating decision-making and cooperation between migrating instances. Consequently the migrating workflow model can greatly enhance the dynamic adaptability of business process and executable environment. Especially, the model adapts to those incompletely defined business process management of multi-terrain, mlti-organization caused by the diverse process rules or executing environment.Accordingly, dynamic adaptability of migrating workflow provides the dynamic adaptable methods and establishes corresponding work mechanism for migrating instances and workplaces. It makes the migrating workflow system to forecast, modify and re-construct its flow when business process rules and workflow services are changed. Thus it ensures that the business process with incomplete explanation can be executed correctly in dynamic workflow environment.There are many aspects about dynamic adaptability of migrating workflow. This study is mainly supported by the National Natural Science Foundation of China under "Research on the methods of migrating workflow object oriented". The process dynamic adaptability, service dynamic adaptability and running environment dynamic adaptability of the migrating workflow are mainly discussed. Firstly, the process dynamic adaptability studies the decision-making ability of the migrating workflow system in order to discover and optimize migrating route and deal with incomplete workflow explanation. Secondly, the service dynamic adaptability focuses on the service substitution mechanism that is object and semantic oriented in order to avoid halt of the business process because of the unusable or changed services. Lastly, the running environment dynamic adaptability provides the cooperative apperceiving and learning method of migrating instances in order to make up the cognitive deficiency of environment. The main contributions of this thesis are described as follows:1. Research on process dynamic adaptability of migrating workflow. In the migrating workflow, because of the incomplete workflow explanation, all the workplaces that migrating instance needs are not planed at the beginning. So the system must adjust Itinerary graph according to the the change of the process. If the migrating workflow system is provide with the ability that may plan activities and workplaces during flow running, it has process dynamic adaptability. Chapter 3 presents an object-oriented migrating decision-making method. Improving on the basic genetic algorithm, this method provides an improved hybrid genetic algorithm with enhanced EAX operator and reinforcement mutation operator. Large experiments on TSP instances show that this method outperforms other heuristic methods in route plan. Based on this method, the migrating instance can dynamically adjust its workplaces and complete the task with the excellent use of resources. This method is validated in the environment of migrating workflow and shows that the workplace may be reasonable adjusted to enhance the self-adaptation ability of business process.2. Research on service dynamic adaptability of migrating workflow. The workplace provides running service (such as migraing in, migrating out, safety protection and so on) and workflow service (such as data service, automatically transfer service and so on). The workplace logic abnormity mainly denotes that the workflow service that the workplace provides is changed, is not carried through according to a plan or is not produced expected results. The workflow service dynamic is that when a service is not accessed casually another equivalent service may be found and substituted to complete the same task. Chapter 4 presents a service ontology substitution mechanism based on the description of ontology and provides a flexible migrating workflow system framework. When the migrating instance finds that the service is changed, it may find substituted service to execute. When service deletion, service invalidation, and service overtime or service abnormity appear, the migrating instance may substitute a new service for exceptional service to ensure the continuous execution of workflow. This mechanism makes the workflow changeable, namely that in order to adjust the existing flow it need not redesign a new work folw. Thus the resources can be made the best use and the workflow efficiency can be enhanced greatly.3. Research on running environment dynamic adaptability of migrating workflow. The workplace provides a running environment to the migrating instance, in which the migrating instance can obtain a service list that the current workplace may provide and the information about other instances that rest on the same workplace. If the migrating workflow system may response and deal with those abnormity brought by workplace physical fault, it poses the ruuning environment dynamic adaptability. Because above abnormity, in the running environment the migrating instance apperceives some partly incomplete information. Chapter 5 investigates a planning model and an efficient, dynamic and flexible method which makes the migrating instance to possess partly perceptive, competitively cooperative and self-learning abilities. The migrating instance makes use of this incomplete information to make an initial plan and obtains a feasible strategy set. Afterwards, the migrating instance obtains the recent information of its fellow. According to this information and its initial planned strategy set, the migrating instance makes incomplete global plan. The planning method of the migrating instance makes the migrating instance to adapt to multiform changes and enhances the self-adaptive ability of the system.The main innovative contributions of this thesis are:1. This thesis proposes a process dynamic adaptability method based on optimized planning algorithm of migrating rout. This method is based on the traveling salesman problem (TSP) model in which a city denotes a workplace, and then a hybrid genetic algorithm RMGA with improved EAX operator and reinforcement mutation operator is proposed. The core of RMGA lies in the using heterogeneous paring selection instead of random paring selection in EAX and the construction of reinforcement mutation operator, named RL-M, by modifying the Q-learning algorithm and applying it to those individuals generated from modified EAX. The experimental results show that RMGA outperformed the known genetic algorithm in the quality of solutions and the running time. Based on the heuristic transcendent knowledge, the system dynamically plans the migrate route using this method.2. This thesis proposes a service dynamic adaptability method based on workflow service substitution mechanism. This method incorporates knowledge ontology to provide a service ontology substitution mechanism. This mechanism makes the migrating instance to find substituted service or resource to continually execute when preconcerted service or resource cannot be obtained. This thesis also provides a method that can realize this mechanism in the migrating workflow model. The ontology substituting mechanism may realize automatic service-finding and the service dynamic combination based on domain ontology. Under the support of the domain ontology and the base of similarity measurement in ontology, the relevancy measurement between services is computed and service combination is formed.3. This thesis proposes a running environment dynamic adaptability method based on local planning algorithm of migrating route. In the running environment, the migrating instance apperceives incomplete information. So the environment may be modeled by partially observable Markov decision processes (POMDP). On this condition a local route planning algorithm algorithm is provided to solute such uncertain POMDP approximately optimal strategy. The certain limited historical information of the migrating instance is kept and incorporated with the belief state--probability distribution over all of the possible states to decide the optimal strategy. The validity of this method is validated through the simulation on the instance of migrating workflow.The dynamic adaptability of migrating workflow that this thesis proposes has been testified in emulational experiments. But the dynamic adaptability problem is complex, so there are many aspects to be improved. 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 correctness validation in workflow process alteration only depends on the tool of process definition, but its granularity is insufficient. So multilayer partition and multilayer validation of the modified process model should be made to ensure its correctness.2. Some theoretical problems of service adaptability should be solved, such as the semantic and formalized methods of the migrating workflow service variety. Next, we should summarize and conclude from application practice in order to establish a general classified system about service variety. 3. From the point of view of the running environment adaptability implementation, the problems of local least path and repeat path should be further investigated. We should further improve on route planning algorithm.Based on above investigation work, we hope to make a further analysis, comparison and improvement.