Search results

The purpose of this paper is to demonstrate that process verification has matured to a level where it can be used in practice. This paper reports on new verification techniques that can be used to assess the correctness of real‐life models.

The proposed approach relies on using formal methods to determine the correctness of business processes with cancellation and OR‐joins. The paper also demonstrates how reduction rules can be used to improve the efficiency. These techniques are presented in the context of the workflow language yet another workflow language (YAWL) that provides direct support for 20 most frequently used patterns found today (including cancellation and OR‐joins). But the results also apply to other languages with these features (e.g. BPMN, EPCs, UML activity diagrams, etc.). An editor has been developed that provides diagnostic information based on the techniques presented in this paper.

The paper proposes four properties for business processes with cancellation and OR‐joins, namely: soundness, weak soundness, irreducible cancellation regions and immutable OR‐joins and develop new techniques to verify these properties. Reduction rules have been used as a means of improving the efficiency of the algorithm. The paper demonstrates the feasibility of this verification approach using a realistic and complex business process, the visa application process for general skilled migration to Australia, modelled as a YAWL workflow with cancellation regions and OR‐joins.

Business processes sometimes require complex execution interdependencies to properly complete a process. For instance, it is possible that certain activities need to be cancelled mid‐way though the process. Some parallel activities may require complex “wait and see” style synchronisation depending on a given context. These types of business processes can be found in various domains, such as application integration, B2B commerce, web service composition and workflow systems. Even though cancellation and sophisticated join structures are present in many business processes, existing verification techniques are unable to deal with such processes. Hence, this paper plays an important role in making process verification a reality.

The increasing popularity of XML has generated a lot of interest in query processing over graph‐structured data. To support efficient evaluation of path expressions structured indexes have been proposed. Extending the proposed indexes to work with large XML graphs and to support intra‐ or inter‐document links requires a lot of computing power for the creation process and a lot of space to store the indexes. Moreover, the efficient evaluation of ancestors‐descendants queries over arbitrary graphs with long paths is a severe problem. This paper aims to propose a scalable path index which is based on the concept of 2‐hop covers as introduced by Cohen et al.

The problem of efficiently managing and querying XML documents poses interesting challenges on database research. The proposed algorithm for index creation scales down the original graph size substantially. As a result a directed acyclic graph with a smaller number of nodes and edges will emerge. This reduces the number of computing steps required for building the index. Thus, computing time and space will be reduced as well. The index also permits ancestors‐descendants relationships to be efficiently evaluated. Moreover, the proposed index has a nice property in comparison to most other work; it is optimized for descendants‐or‐self queries on arbitrary graphs with link relationships.

In this paper, a scalable path index is proposed. It can efficiently address the problem of querying large XML documents that contain links and have cycles. Cycles in the graph stress path‐indexing algorithms. An overview about 2‐hop cover and the algorithms that used to build the index are given.

This paper works on the updating problem. Since the construction of the index is quite complex its construction make sense for some time. However, this means it is currently dealing with the problem of updating XML‐documents.

This paper presents an efficient path index that can test the reachability between two nodes and evaluate ancestors‐descendants queries over arbitrary graphs with long paths.

This paper seeks to propose a methodology based on Petri nets to evaluate the reliability parameters of a screening system in paper industry. The effects of failures and courses of action on the system performance have also been investigated.

Generalized stochastic Petri nets (GSPN), a class of Petri nets, has been used to model the interactions amongst the active/standby units of the system; and Markovian approach has been used to evaluate the reliability parameters. The data related to equipments' operational behavior were collected, processed and quantified. Using the data, reliability analysis of system in the long run conditions has been carried out. The sensitivity analysis has been performed to study the effect of failure/repair rates of each unit of the system on system performance.

The methodology adopted in this paper provides a better understanding on the behavior of the system through its graphical representation. The reachability graph generated with Petri net model helps to identify the state space evolution of the system.

Reliability analysis of a screening system of the paper industry presented in this paper will help management in deciding upon the maintenance strategy to be adopted with the objective of improving the performance of the system and consequently reducing the operational and maintenance costs.

Deadlock is a rather undesirable phenomenon and must be well solved in flexible manufacturing systems (FMS). This paper aims to propose a general iterative deadlock control method for a class of generalized Petri nets (GPN), namely, G-systems, which can model an FMS with assembly and disassembly operations of multiple resource acquisition. When given an uncontrolled G-system prone to deadlocks, the work focuses on the synthesis of a near-optimal, non-blocking supervisor based on reachability graph (RG) analysis.

The concept of a global idle place (GIP) for an original uncontrolled G-system is presented. To simplify the RG computation of an uncontrolled G-system, a GIP is added temporarily to the net model during monitor computation steps. Starting with one token and then by gradually increasing the number of tokens in the GIP at each iteration step, the related net system is obtained. The minimal-covered-set of all bad markings of the related net system suffering from deadlock can be identified and then removed by additional monitors through an established place-invariant control method. Consequently, all related systems are live, and the GIP is finally removed when the non-blockingness of the controlled system is achieved. Meanwhile, the redundancy of monitors is also checked.

A typical G-system example is provided to demonstrate the applicability and effectiveness of the proposed method. Experiments show that the proposed method is easy to use and provides very high behavioral permissiveness for G-system. Generally, it can achieve an optimal or a near-optimal solution of the non-blocking supervisor.

In this work, the concept of GIP for G-systems is presented for synthesis non-blocking supervisors based on RG analysis. By using GIP, an effective deadlock control method is proposed. Generally, the proposed method can achieve an optimal or a near-optimal, non-blocking supervisor for an uncontrolled G-system prone to deadlocks.

The purpose of this paper is to propose a new generic hybrid Petri Net (PN) model combined with the lowest makespan cut (LMC) for job shop scheduling problems in mold manufacturing to minimize the makespan of the mold part manufacture schedule.

The LMC algorithm finds a solution close to the optimal solution. The searching of the LMC algorithm starts from the lowest estimated makespan (lowest makespan). Almost all of the lowest makespans (LM) are infeasible makespans. A shifting percentage (SP) is added to the LM to obtain the shifting makespan (SM). The SM is compared with the completion time computed from the reachability tree of the Petri Net (PN) model. If the completion time is greater than the SM, the corresponding branch is cut from the reachability graph, and the SM will be compared with another branch from the reachability tree. There are two scenarios. In the first scenario, there is no feasible solution resulting from the comparison of the completion time and the SM, because the SM is lower than all of the feasible solutions. Therefore, the SP is used to increase the SM. On the contrary, in the second scenario, there is a feasible solution: the SP is used to reduce the SM. In the first scenario, a makespan that is lower than the optimal makespan is found. In the second scenario, a makespan that is greater than the optimal makespan is found. After getting close to bounds of the optimal makespan, the least makespan found in the bounds is the best solution.

The integration of the Petri Net (PN) model and the LMC algorithm can help to improve the production efficiency. In a case study, the proposed algorithm is being compared with other heuristical methods which are practical examples of mold makespans based on the shortest and the longest processing times. The schedule or the sequence obtained by the proposed algorithm is 30% less than the other methods.

This research will consider scheduling multiple mold. The mold design and the mold testing phase are not considered.

The time to produce a mold is very important. Reducing the mold production time will provide more time for mold assembly and testing. The aim of LMC algorithm is minimize the makespan. The time to produce a mold is reduced by finding the best sequence of the jobs and machines.

This paper proposes the new generic hybrid Petri Net model combined with LMC for job shop scheduling problem in the case of mold making shop to optimize the makespan of mold parts scheduling.

Sustainability has been on the executive agenda for years and it is now one of the fastest growing supply chain management trends. The purpose of this paper is to analyze the barriers for the adoption and implementation of the sustainable supply chain management (SSCM) concept.

This study has been divided into two phases such as identification of barriers and qualitative analysis. First, to identify the most influential barriers, the authors offer a systematic literature review, taking 188 papers published from 2010 to November 2016 into account. The investigation phase led to the selection of 15 barriers based on the literature in consultation with industrial experts and academicians. Second, the interpretive structural modeling qualitative analysis was used to find out the mutual influences between the 15 barriers by a survey.

Further, the authors propose and illustrate the cross-impact matrix multiplication applied to classification analysis to test a framework that extrapolates SSCM barriers and their relationships. “Inadequate information technology implementation” has been identified as the most important barrier that may force organizations to implement SSCM practices to ensure their business sustainability.

The authors presented some limitations in their research in some fields which could allow new researchers and practitioners to conduct the future research to grow in different dimensions.

Practitioners or policymakers usually are not familiar with these types of research works; that is why most of these surveys remain theoretical and conceptual. Future investigation needs to be done in practical application domain instead of merely giving opinions.

Based on the authors’ research, the researchers have more attention to work in conceptual analysis due to other fields, but the authors believe that even with the implementation of SSCM, many remarkable areas still exist for future research which could help in development. The authors also provide more details in this paper.

The purpose of this paper is to resolve the problem of complex system diagnosis with unobservable events such as Hall thruster.

Fault class is defined by unobservable transitions subset. Every fault class is departed into four levels of alarm. The level of alarm for a fault class is identified by constructing basis reachability graph and computing j vector and basis marking. Certain factor values of diagnosis results are given by introducing two fuzzy operators. A two‐directional reasoning strategy is adopted which are forward reasoning and backward reasoning.

Using basis reachability graph and notions of basis marking and j vector, fuzzy Petri net with unobservable transitions can resolve the diagnosis problems with high accuracy and efficiency.

The relationship between unobservable events must be known.

The method shows its superiority when it is applied to unobservable systems such as spacecraft.

A novel fuzzy Petri net framework for unobservable system multi‐fault diagnosis is put forward which introduces some new ideas.

The purpose of this paper is to demonstrate the use of Petri nets in a job shop setup for the improvement in the utilization of machines.

The study discusses concepts such as reachable state, token and matrix equations set, and demonstrates the improvements in machines’ utilization in a job shop. It makes use of algorithms to generate reachable markings to obtain utilization. The study not only describes the application of theory, but also extends the body of knowledge on Petri nets and job shops.

In this study, machines’ utilization has been studied in a job shop with six machines and eight products. The study finds that substantial utilization improvement in job shop set up can be obtained through the application of Petri nets. The study also exposes that Petri nets are mostly used for machines, jobs and tools scheduling problems, but its use in machines’ utilization is neglected. The framework and application presented here along with generalizable findings, is the first to report about machine utilization improvement in job shop manufacturing environment.

Job shops are characterized by high unit production cost, low investments, low volume and high variety, complex flows, flexible and skilled work force, general purpose machines, high material handling; resulting in poor utilization of machines. Therefore, the findings of this study can help in reducing such costs through better machine utilization. This can help in increasing the competitiveness of the companies.

The contribution of study lies in investigating and improving stage wise utilization in a job shop setup. It has never been reported before.

The purpose of this paper is to create the inventory scheduling model for supply chain system.

Aiming at the problems of analysis and modeling of multi‐agent system, an agent‐oriented Petri net (AOPN) model is proposed by introducing the characteristics of agent based on Petri net, and formalization definition of AOPN is presented. Combined with the inventory scheduling in supply chain system, inventory scheduling model based on AOPN is constructed. On the basis of the inventory scheduling model, its program model is designed. Then the reachability of the inventory scheduling model is analyzed and its soundness is verified.

The AOPN model and inventory scheduling model based on AOPN in supply chain system are found.

The reasonable basic function design of various agents are main limitations.

A very useful tool of analysis for the modeling of inventory scheduling in supply chain system.

The paper presents a new modeling method of inventory scheduling in supply chain system. This paper is aimed at researchers and engineers.

The key objectives of this study were to investigate the interactions among the lean, green management practices and organizational sustainable performance measures and explore the possibility of simultaneous implementation of these concepts for improving the organizational sustainable performance.

Using the interpretive structural modeling (ISM) technique, the interactions among the lean, green practices and organizational sustainable performance measures were established. A focus group which consisted of purposively selected 15 experts was utilized in the primary data collection.

In Sri Lankan context, water and material consumption reduction, energy efficiency, water pollution and greenhouse gas reduction were identified as the dominant green practices, while pull production, lot size reduction, continuous improvement, preventive maintenance, employee involvement and cycle time reduction were the dominant lean practices. Inventory level, profitability, quality, cost, employee satisfaction, customer satisfaction, lead time, resources consumption (material, water, energy) and waste generation were determined as the dominant sustainable performance measures. The resulting ISM-based structural model which consisted of eight levels concluded that firstly lean practices influence the green practices and afterward green practices affect the sustainable performance measures.

The aim of this study was to develop a hypothetical structural model to explain the interactions among the lean, green management practices and organizational sustainable performance measures. But this hypothetical model was not empirically tested in the current study. So further study is required to empirically test the proposed model.

Currently organizations who practice for sustainable performance engages, lean and green practices separately without understanding on which practices are stared when and how. So, through the findings of this study, organization who desire to improve the sustainable performance are recommended to begin the journey with lean practices and subsequently move in to green and handle both lean and green initiatives through one functional unit.

The existing literature does not possess a model for explaining the lean–green synergy and organizational sustainable performance and this study successfully fills this gap. Also the study proposes for the practitioners, when and how the lean and green practices should be initiated and implemented for rising the sustainable performance of an organization.