Browsing by Author "Wang, Feng-Jian"

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A Delegation Framework for Task-Role Based Access Control in WFMS
(2011-05-01)
Hsu, Hwai-Jung
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Wang, Feng-Jian
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資訊工程學系
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Department of Computer Science
Access control is important for protecting information integrity in workflow management system (WfMS). Compared to conventional access control technology such as discretionary, mandatory, and role-based access control models, task-role-based access control (TRBAC) model, an access control model based on both tasks and roles, meets more requirements for modern enterprise environments. However, few discussions on delegation mechanisms for TRBAC are made. In this paper, a framework considering temporal constraints to improve delegation and help automatic delegation in TRBAC is presented. In the framework, the methodology for delegations requested from both users and WfMS is discussed. The constraints for delegatee selection such as delegation loop and separation of duty (SOD) are addressed. With the framework, a sequence of algorithms for delegation and revocation of tasks are constructed gradually. Finally, a comparison is made between our approach and the representative related works.
A distributed server architecture supporting dynamic resource provisioning for BPM-oriented workflow management systems
(2010-08-01)
Tsai, Ching-Hong
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Huang, Kuo-Chan
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Wang, Feng-Jian
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Chen, Chun-Hao
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資訊工程學系
Workflow management systems have been widely used in many business process management (BPM) applications. There are also a lot of companies offering commercial software solutions for BPM. However, most of them adopt a simple client/server architecture with one single centralized workflow-management server only. As the number of incoming workflow requests increases, the single workflow-management server might become the performance bottleneck, leading to unacceptable response time. Development of parallel servers might be a possible solution. However, a parallel server architecture with a fixed-number of servers cannot efficiently utilize computing resources under time-varying system workloads. This paper presents a distributed workflow-management server architecture which adopts dynamic resource provisioning mechanisms to deal with the probable performance bottleneck. We implemented a prototype system of the proposed architecture based on a commercial workflow management system, Agentflow. A series of experiments were conducted on the prototype system for performance evaluation. The experimental results indicate that the proposed architecture can deliver scalable performance and effectively maintain stable request response time under a wide range of incoming workflow request workloads. (C) 2010 Elsevier Inc. All rights reserved.
A Study to Improving Anomaly Detection in a TS Workflow
(2016)
Wang, Feng-Jian
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Thanh-Thuy Thi Nguyen
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Lu, Tennyson
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資訊工程學系
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Department of Computer Science
The analysis for the behavior of the artifacts adopted in a workflow can help preventing the execution errors. A temporal (structured) workflow, TS Workflow, is described with the min and max execution time intervals for each process and modeled by control structures (Sequence, AND, XOR, Loop). In the past, the anomalous behaviors of artifacts in a workflow are redefined to simplify artifact analysis in a workflow. However, some anomalies detected in the previous work might not occur if the temporal factors are considered in each process, because their corresponding processes cannot run continuously or concurrently due to temporal factors. In this work, the analysis work is improved by filtering out above anomalies in a TS workflow. Our work also handles the loop structure that complicates the analysis work and was not concerned in conventional analysis works.
An iterative expanding and shrinking process for processor allocation in mixed-parallel workflow scheduling
(2016-07-20)
Huang, Kuo-Chan
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Wu, Wei-Ya
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Wang, Feng-Jian
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Liu, Hsiao-Ching
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Hung, Chun-Hao
Parallel computation has been widely applied in a variety of large-scale scientific and engineering applications. Many studies indicate that exploiting both task and data parallelisms, i.e. mixed-parallel workflows, to solve large computational problems can get better efficacy compared with either pure task parallelism or pure data parallelism. Scheduling traditional workflows of pure task parallelism on parallel systems has long been known to be an NP-complete problem. Mixed-parallel workflow scheduling has to deal with an additional challenging issue of processor allocation. In this paper, we explore the processor allocation issue in scheduling mixed-parallel workflows of moldable tasks, called M-task, and propose an Iterative Allocation Expanding and Shrinking (IAES) approach. Compared to previous approaches, our IAES has two distinguishing features. The first is allocating more processors to the tasks on allocated critical paths for effectively reducing the makespan of workflow execution. The second is allowing the processor allocation of an M-task to shrink during the iterative procedure, resulting in a more flexible and effective process for finding better allocation. The proposed IAES approach has been evaluated with a series of simulation experiments and compared to several well-known previous methods, including CPR, CPA, MCPA, and MCPA2. The experimental results indicate that our IAES approach outperforms those previous methods significantly in most situations, especially when nodes of the same layer in a workflow might have unequal workloads.
Analyzing Artifact Anomalies in a Temporal Structural Workflow for SBS
(2014-01-01)
Wang, Feng-Jian
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Mandalapu, Parameswaramma
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資訊工程學系
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Department of Computer Science
A service-based system (SBS) defined with minimum and maximum execution time can be easily transferred into a temporal structured workflow. The analysis technique on a temporal structured workflow can thus be applied on SBS. In the past, there were several researches working on artifact anomaly detection in a workflow. Their results are useful and have been published. However, their works does not consider temporal factor and the anomalies detected may not exist in a real system. In other word, they are less effective in a temporal structural workflow (TS workflow). Neither for SBS. Besides, the time complexity of these methods are NP, not efficient either. In this paper, we re-define the anomalous behaviors and develop an approach to discover artifact anomalies in a TS workflow. In the approach, we design several algorithms to detect the anomalies defined. By using our approach, workflow and SBS designers can detect artifact anomalies more precisely inside their TS workflow and thus might prevent run-time errors more effectively.
Analyzing inaccurate artifact usages in a workflow schema
(2006)
Wang, Feng-Jian
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Hsu, Chia-Lin
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Hsu, Huin-Jen
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資訊工程學系
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Department of Computer Science
There are many works done and successful results for workflow, but few researchers work in artifact analysis. A workflow execution may fail because of incorrect structures, or resource conflict. It might also fail due to inaccurate artifact manipulation e.g., inconsistency between data flow and control flow, contradictions between artifact operations.... etc. This paper identifies six types of artifact inaccuracy impacting on workflow execution. Moreover, algorithms to detecting artifact inaccuracies in workflow specifications are demonstrated.
Constructing a Service Software with Microservices
(2018-01-01)
Wang, Feng-Jian
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Fahmi, Faisal
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資訊工程學系
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電機資訊國際碩士學位學程
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Department of Computer Science
The microservice architecture is a variation of a Service-Oriented Architecture (SOA) that allows a service to be broken down into a number of smaller but independently concurrent rimming units so that both performance and maintainability of the application can get a big improvement. In this paper, we introduce an approach to constructing a software with layered and distributed microservices using object-oriented specifications. The proposed approach could increase the concurrency of the application system and thus improve the performance and could increase the reusability of microservices.
Detecting artifact anomalies in business process specifications with a formal model
(2009-10-01)
Wang, Ching-Huey
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Wang, Feng-Jian
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資訊科學與工程研究所
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Institute of Computer Science and Engineering
Many business process analysis models have been proposed, however there are few discussions for artifact usages in workflow specifications. A well-structured business process with sufficient resources might fail or yield unexpected results dynamically due to inaccurate artifact specification, e.g. an inconsistency between artifact and control flow. or contradictions between artifact operations. This paper, based on our previous work, presents a model for describing the input/output of a workflow process and analyzes the artifact usages upon the model. This work identifies and formulates thirteen cases of artifact usage anomalies affecting process execution and categorizes the cases into three types. Moreover, the methods for detecting these anomalies with time complexities O(n(2)) less than O(n(3)) in previous methods, are presented. Besides, the paper uses an example to demonstrate the processing of them. (C) 2009 Elsevier Inc. All rights reserved.
Dynamic Activities on An Agent-based Workflow Management System
(2005)
Wang, Jian-Wei
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Li, Chi-Cheng
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Wang, Feng-Jian
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資訊工程學系
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Department of Computer Science
Workflow management systems (WfMSs) are usually designed to run with the workflow (process) definitions and artifact definitions from repository. The static characteristics for process definitions might reduce the practicability of the systems. The cost to develop a WfMS is so high that it is reasonable to take the flexibility of system architecture into account. In this paper, we present an approach to adapt to dynamic changes on workflow definitions with agents. In our agent-based workflow system, the definition of a workflow can be modified by the agent itself. Therefore, agents can modify their guidance for workers, and the system will be more flexible to meet the specification modification.
Dynamic Provisioning of a Parallel Workflow Management System
(2008)
Tsai, Ching-Hong
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Huang, Kuo-Chan
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Wang, Feng-Jian
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資訊工程學系
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Department of Computer Science
Most work/flow management systems nowadays are based on centralized client/server architecture. Under this architecture, the response time of request might increase unacceptably when the number of users who login to the system increase quickly and a large amount of requests are sent to the centralized server within a short time period. Parallel server architecture could help to resolve the performance bottleneck of a single server. However, a static parallel architecture with a fixed number of servers is not efficient at resource utilization because the numbers of users and their requests usually change time by time, especially for big and fast changes. This paper presents an effective architecture of dynamic resource-provisioning and then the implementation for a parallel workflow management system. There are a series of experiments conducted and the results indicate that it is an effective approach to handling the time-varying workloads in real world WfMS.
Dynamic Resource Provisioning for Interactive Workflow Applications on Cloud Computing Platform
(2010)
Zhou, Hui-Zhen
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Huang, Kuo-Chan
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Wang, Feng-Jian
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資訊工程學系
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Department of Computer Science
Cloud computing opens new opportunities for application providers because with the policy "add as needed and pay as used" they can economize the cost for computing resources. In cloud environments, issues such as resource allocation and dynamic resource provisioning based on users' QoS constraints are yet to be addressed for interactive workflow applications. This paper develops an effective load metric, remaining tasks, for interactive workflow applications. Based on this metric load dispatching and dynamic resource provisioning approaches are proposed which outperform existing methods under a series of simulation evaluations. Experimental results show that the proposed approaches offer application providers better maintenance of QoS-satisfied response time under time-varying workload, at the minimum cost of resource usage.
Improving the Detection o Sequential Anomalies Associated with a Loop
(2019-01-01)
Fahmi, Faisal
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Huang, Pei-Shu
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Wang, Feng-Jian
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資訊工程學系
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電機資訊國際碩士學位學程
Workflow models are widely applied in business software design. A workflow model contains a set of systematic ordered tasks to achieve designated business goal(s) under the designed flow control. Analyzing artifact usage during design phase can prevent unexpected artifact result due to abnormal artifact operation(s). A sequential anomaly indicates a pair of activities operating on the same artifact that can result in redundant write or missing production. On the other hand, the iteration of a loop structure in a workflow cannot be statically analyzed, thus, detecting process of artifact anomalies in a loop is costly. In this paper, we present an effective method to detect all anomalies associated with a loop by removing the redundant computation due to the repeated structure of the body and control in the iterations. After the removing, the anomalies can be detected on a single iteration generated instead. Here, the process of anomaly detection is now simplified into two phases: First, a workflow model is transformed into a corresponding C-tree structure and next, the proposed anomaly detection methodology is applied to the C-tree. Compared with current approaches, our method can reduce the space complexity and decrease the execution times of anomaly detection as linear.
Improving Workflow Anomaly Detection with a C-Tree
(2017-01-01)
Wang, Feng-Jian
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Chang, Alex
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Lu, Tennyson
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資訊工程學系
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Department of Computer Science
To guarantee the correctness of workflow execution, it is essential to analyze the structural and artifact integrity of workflows. The current best approach of artifact workflow anomaly detection is O(vertical bar E vertical bar) for structured workflows, however, each of the anomalies returned in the approach contains (artifact, operator) at each workflow node. In this paper, we present an innovative methodology which contains the following two characteristics: 1) A C-Tree (defined in Section 3) structure which separates sequential and parallel issues in workflow analysis and increases the convenience and elegancy of anomaly detection; and 2) A loop-reduction method which helps lower the size of nodes to be analyzed while not losing the abilities of detecting anomalies within workflow models. The anomaly detection is done by 1) transforming the BPMN into the C-Tree, 2) and detecting the anomaly in the C-tree. Compared with current best approach, 1) Our method can show the first operator and its location of an anomaly detected directly, although it cannot speed up the execution time, 2) The execution times of anomaly detection inside loop is decreased, and 3) Our method can detect concurrent (parallel) workflow anomaly based on C-Tree.
Online Scheduling of Workflow Applications in Grid Environment
(2010)
Hsu, Chih-Chiang
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Huang, Kuo-Chan
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Wang, Feng-Jian
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資訊工程學系
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Department of Computer Science
Scheduling workflow applications in grid environments is a great challenge, because it is an NP-complete problem. Many heuristic methods have been presented in the literature and most of them deal with a single workflow application at a time. In recent years, there are several heuristic methods proposed to deal with concurrent workflows or online workflows, but they do not work with workflows composed of data-parallel tasks. In this paper, we present an online scheduling approach for multiple mixed-parallel workflows in grid environments. The proposed approach was evaluated with a series of simulation experiments and the results show that the proposed approach delivers good performance and outperforms other methods under various workloads.
Online scheduling of workflow applications in grid environments
(2011-06-01)
Hsu, Chih-Chiang
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Huang, Kuo-Chan
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Wang, Feng-Jian
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資訊工程學系
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Department of Computer Science
Scheduling workflow applications in grid environments is a great challenge, because it is an NP-complete problem. Many heuristic methods have been presented in the literature and most of them deal with a single workflow application at a time. In recent years, several heuristic methods have been proposed to deal with concurrent workflows or online workflows, but they do not work with workflows composed of data-parallel tasks. In this paper, we present an online scheduling approach for multiple mixed-parallel workflows in grid environments. The proposed approach was evaluated with a series of simulation experiments and the results show that the proposed approach delivers good performance and outperforms other methods under various workloads. (C) 2010 Elsevier B.V. All rights reserved.
Reducing Anomaly Detection in a TS Workflow
(2015-01-01)
Wang, Feng-Jian
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Thanh-Thuy Thi Nguyen
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Mandalapu, Parameswaramma
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資訊工程學系
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Department of Computer Science
Nowadays workflow management systems (WfMS) are widely used for improving business processes and providing better quality of services. The analysis of workflow can facilitate locating problems in business processes and prevent repeated errors during workflow execution. A temporal workflow is described with the min and max execution time intervals for each process and modeled by control structures (Sequence, AND, XOR, Loop). These time intervals are essential factors for the analysis and anomaly detection in a workflow. In our previous work, we provided redefined definitions for anomalous behaviors and algorithms to detect anomalies within a temporal workflow. However, an essential factor, a loop structure and its temporal effects are not discussed yet. In this paper, our work extends the analysis to the workflows containing loop structure. To simplify the anomaly detection inside the loop, we first transform the loop into an XOR structure branch, perform a series of analyses and then design an algorithm to find the anomalies more efficiently. We also make an analysis for the contribution due to the algorithms.
Scheduling online mixed-parallel workflows of rigid tasks in heterogeneous multi-cluster environments
(2016-07)
Wang, Yi-Rong
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Huang, Kuo-Chan
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Wang, Feng-Jian
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資訊工程學系
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Department of Computer Science
Workflow scheduling on parallel systems has long been known to be a NP-complete problem. As modern grid and cloud computing platforms emerge, it becomes indispensable to schedule mixed-parallel workflows in an online manner in a speed-heterogeneous multi-cluster environment. However, most existing scheduling algorithms were not developed for online mixed-parallel workflows of rigid data parallel tasks and multi-cluster environments, therefore they cannot handle the problem efficiently. In this paper, we propose a scheduling framework, named Mixed-Parallel Online Workflow Scheduling (MOWS), which divides the entire scheduling process into four phases: task prioritizing, waiting queue scheduling, task rearrangement, and task allocation. Based on this framework, we developed four new methods: shortest-workflow-first, priority-based backfilling, preemptive task execution and All-EFT task allocation, for scheduling online mixed-parallel workflows of rigid tasks in speed-heterogeneous multi cluster environments. To evaluate the proposed scheduling methods, we conducted a series of simulation studies and made comparisons with previously proposed approaches in the literature. The experimental results indicate that each of the four proposed methods outperforms existing approaches significantly and all these approaches in MOWS together can achieve more than 20% performance improvement in terms of average turnaround time. (C) 2016 Elsevier B.V. All rights reserved.
Separation of Concerns in Analysis of Artifact Anomalies within Workflow Models
(2016)
Wang, Feng-Jian
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Lu, Tenny
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Hsu, Hwai-Jung
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資訊工程學系
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Department of Computer Science
Workflows which realize parts of business goals in a particular order automate the business processes within enterprises. To guarantee the correctness of workflow execution, analyses on structural integrity of workflows are essential. However, comparing to the sequential activities, the activities executed in orders, the anomalies caused by parallel activities are far more complicated for analysis. Therefore, separation of concerns among sequential and parallel issues while doing analysis can reduce the complexity among analysis time and human recognition. In this paper, we propose an innovative methodology considering sequential and parallel issues separately within workflow models to detect anomalies in a given workflow. As a result, the cost for anomaly detection is lowered and the complexity for human recognition of the anomaly issues is reduced.
The Development of Cloud Computing and Its Challenges for Taiwan
(2012)
Chu, William C.
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Chang, Chih-Hung
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Lu, Chih-Wei
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Chen, Juei-Nan
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Wang, Feng-Jian
Along with the growing attention, cloud computing is not only changing the computing paradigm, but also the style of computing in which dynamically scalable and virtualized resources are provided as services over the Internet. Cloud computing introduces a lot of chances, as well as, challenges in the new trend. Taiwan has been well known as a major Information Communication Technology (ICT) manufacturing traditionally. Many Taiwan\'s hardware products have been top ranked in the global market. Taiwan has realized the trend that Cloud Computing is leading to and has reacted to integrate its resources from the government, industry, academia, and research centers, by initiating strong incentive programs for cloud computing, with an intension to transform an ICT Island into a Cloud Village. In this article, we describe the status of the development of cloud computing technologies and its future challenges for Taiwan.
Using Artifact Flow Diagrams to model Artifact Usage Anomalies
(2009)
Hsu, Hwai-Jung
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Wang, Feng-Jian
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資訊工程學系
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Department of Computer Science
Workflow is a set of tasks which are systematized to achieve certain business goal(s), where the tasks run in a particular order under automatic control. Artifacts, collections of data items, are necessary for task (process) executions in a workflow. However, an execution may yield unexpected results due to improper artifact manipulation: e.g., activities miss artifact or artifact conflict occur at an activity dynamically. Therefore, the analyses on artifact usage in design phase are very important for quality insurance. This paper presents a model of artifact flow diagrams to state the artifact usage anomalies in processes transmitting artifacts based on DCDC, Distinct Control and Data Channel, model. There are four types of artifact usage anomalies identified in DCDC and the formal statement of each anomaly is described correspondingly for future study of anomaly search.