A Grammar-Based Process Modeling and Simulation Methodology for Supply Chain Management Mohsen Mohammadi1,*, Muriati Bt. Mukhtar1, and Hamid Reza Peikari2 1
Information Science and Technology, Universiti Kebangsaan Malaysia, Bangi, 43600, Malaysia
[email protected] 2 Graduate School of Business, Universiti Kebangsaan Malaysia, Bangi, 43600, Malaysia
Abstract. In order to respond to customer demands, supply chains must be rapidly reconfigured and evaluated. This has given rise to supply chain simulation as an important tool to aid in the evaluation of supply chain configurations. Part of the reconfigurations involved designing and redesigning business processes. Hence, business process simulation is an integral part of supply chain simulation. Supply chain simulation models are usually large-scale complex models. It is thus usual for the simulation experts to get overwhelmed with the simulation process itself. This paper intends to propose a methodology, combining two approaches (i.e. grammar-based business process modeling and simulation) to facilitate process thinking (reengineering). This methodology bridges the gap between business process modeling and simulation by providing the grammatical approach. This paper presents a novel approach to design business processes based on grammar-based process modeling, eventdriven process chains (EPC) and discrete event simulation. This paper illustrates that the grammar-based process modeling approach is applicable to the simulation of dynamic systems such as supply chains as well as representing detailed description of the processes and events. More detailed and advanced analysis, and discussions will be reported in future papers. Keywords: Event-driven process chain, grammar-based modeling, process simulation, supply chain, Business Process Reengineering.
1 Introduction The uncertainties in business environment change business models in supply chain. Therefore, it is needed to create/change business process in the shortest possible time to respond to the uncertainties of environment. In the design of new business processes, simulation facilitates the validation of the processes to ensure that they will work as designed. Simulation is used to evaluate supply chain performance and is an integral part of the decision making process in supply chain management. Business process-based simulation provides a precise, visual method to analyze and compare the performance before and after business process engineering [1]. For a *
Corresponding author.
H. Badioze Zaman et al. (Eds.): IVIC 2011, Part I, LNCS 7066, pp. 77–86, 2011. © Springer-Verlag Berlin Heidelberg 2011
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manufacturing supply chain, manufacturing patterns such as manufacturing process model, which focus on process modeling, process management, process analysis, and process reengineering [2] will form an important input in the supply chain simulation model. As such, in order to develop supply chain simulation models, the modeler is required to use several approaches and tools in order to capture the important facets of the supply chain. Tools such as the Business Process Modeling (BPM), Business Process Simulation (BPS) and discrete event simulation are usually used. However, these tools have limitations and they need to be complemented by other tools. For instance, Business Process Modeling (BPM) has a static structured approach to business process improvement. It provides a holistic approach on how the business operates by documenting the business processes. However, BPM does not provide any information about the dynamics of the business and how the changes in business process with the minimum risk is possible. To provide a dynamic approach to the business and to consider the impacts of change in such dynamics without risk, the concept of Business Process Simulation (BPS) was developed by researchers and practitioners [3]. However, the diagrams in Business Process Modeling and Business Process Simulation are not sufficient to describe the details of a complex system and its processes [4]. There are numerous studies about Business Process Reengineering (BPR), in which each have used different methodologies. For example, [5] have introduced a methodology based on five business process modeling languages to integrate business process. [6] have proposed a general framework to assess a reengineering project, from its strategic planning stage to post-implementation phases [7] on the other hand have proposed a conceptual model to demonstrate the links between organizational re-structuring and behavioral changes to reengineer business processes. All of such studies have focused on business processes while in order to link between process modeling and process simulation; it is needed to have descriptive details of events and processes. Therefore, it is needed to apply a Grammar-Based Process Modeling. Applying such an approach, can improve the simulation of complex systems such as supply chains. Moreover, using a grammar-based process modeling approach is essential to prevent repeating the sub-processes and events of the system. The objective of this paper is to apply a Grammar-Based Process Modeling and Simulation methodology for supply chain management to illustrate more details of the system and its processes. [8] developed a simulation model by proposing an analytical framework for integrated logistic chain and this paper by using Arena 10 applies a simulation model based on numerical example in [8]; however it does not show the key performance indicators (KPI) and optimization of the model but show the possibility of using the information in simulation and analyzing them to have the results.
2 Literature Review The grammatical approach to design and redesign supply chain processes has received some attention. It is because this approach can balance and integrate the use of the other process modeling approaches [9]. MIT process handbook recommends the use of grammar-based approach to model the organizational and system processes [10]. Using this approach, each of the processes of a supply chain can be further described, modeled and modularized in more detailed activities and processes. The representation of the supply chain processes using this approach is easy to maintain because the processes can be described in hierarchical chunks [11].Many process
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simulation tools can be integrated into the manufacturing process, and can be used to reengineer and optimize the manufacturing process model which lead to the improvement of many performance indices. Process models can be developed and supported by different systems such as workflow management system which support the decision making of managers in the business environment [2]. Business Process Simulation is an important part of the design and redesign of business processes. It provides quantitative reports about the impacts of a process design on process performance. Moreover, it provides quantitative evidences to decide the best process design. Simulation of business processes overlap with the simulation of other event systems [12].Simulation has enabled companies to deal with the impacts of the changes in their sites’ parameters without any unwanted or uncalculated effects on their operations and outputs. Business processes and companies knowledge can become much more transparent and understandable with an explicit, standard documentation [13]. The EPC [14] has been developed in 1992 by the team of August-Wilhelm Scheer at the Saarbrücken University in a joint research project with SAP AG. for modelling business processes with the goal to be easily understood and used by business people. The basic idea of EPC is that events trigger functions, or the executed functions cause events. The activities of a business process can be model by functions, and events are created by processing functions[15]. Three different tools applicable for BPS are process execution, process modeling and simulation. Jansen-Vullers and Netjes [12] developed a framework to find strengths and weaknesses of simulation modeling and process modeling tools. As shown in the Table 1, these tools for each of the evaluation criteria ranges from very bad (– –) and bad (-) to neutral (+/–), good (+) and very good (++). Table 1. Modeling capabilities [4] Feature Ease of model building Formal semantics/verif. Workflow patterns Level of details Animation Scenarios
ARIS + – – ++ + +
FLOWer + –– + ++ –– ––
Arena + +/– + ++ ++ +
3 Model Description As shown in Figure 1, a supply chain model was considered with the following assumptions: Three suppliers: Supplier 1, Supplier 2, Supplier 3 Two Semi-finished manufacturers: Semi-finished manufacturer 1, Semi-finished manufacturer 2 :One Final manufacturer: Final manufacturer One Distributor: DC Two Warehouse: Warehouse1, Warehouse2 Three Retailers: Retailer1, Retailer2, Retailer3 and Ultimate Customers.
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Fig. 1. The supply chain model
3.1 The Methodology An efficient business process is a critical factor for any business to succeed. Business process modeling facilitates the understanding and analysis of the business process, and business process simulation is an effective technique to evaluate and diagnose business processes in an organization [16]. Due to different issues and shortcomings in time, costs, and users’ skills, the advanced simulation and optimization techniques have not been widely applied [16].The methodology to design business process reengineering modeling is presented in the following flowchart(Figure 2)
Fig. 2. The Methodology of Business Process Reengineering Modeling
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3.2 The Workflow The workflow of the supply chain model illustrated in Figure 3 has been considered without the retailers.
Fig. 3. Workflow diagram
3.3 Grammar-Based Modeling in Supply Chain Process Numerous manufacturing process modeling approaches can be used in process view such as workflow modeling approach and event-driven process chain. Many process simulation tools can be integrated to the manufacturing process model. This optimizes and reengineers the manufacturing process model which lead to the improvement of many performance indices [2]. The element for representing the Supply Chain Process with structural form can be defined [4]: Process: Pi= Event: Ei= Resource: Resource(Ei)={Rj,j=1,2,...•Rj Rj X,X=document or material} Rj= Dependency: Dependency (Di) = 3.4 Modeling the Process In order to represent the workflow of the model, we used Event-Driven Process (EPC) modeling language using ARIS Express 2.3. the events, processes and junctions in this software include and, or, xor. The model has been illustrated in Figure 4. The graph in a model is more intuitive than grammatical model. The above models can represent dynamic process with their representation logic and graphical symbols.
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Fig. 4. Event-driven process chain diagram
3.5 Description of the Events and the Process There are a lot of constraints and relationships among the processes of a supply chain, which can be represented by the grammatical approach [9]. In a model, grammatical model is less intuitive than graph; but diagram cannot represent all information related to processes of a supply chain [9]. Then, in order to ensure the legibility of the model, the basic information of the processes of a supply chain can be represented by diagram as an accessorial tool. Table 2 illustrates the basic information of the grammatical model and provides detailed description of the events and the processes of the model. Table 2. Description of the events and the processes Process Name P1 Produce material 1
Agent Supplier1
P2
Produce material 2
Supplier2
P3
Produce material 3
Supplier3
P4
Produce semi-finished semi-finished product 1 product manufacturer 1 Produce semi-finished semi-finished product 2 product manufacturer 2 Produce final product final product manufacturer
P5
P6
Input Order bill of material 1 Order bill of material 2 Order bill of material 3 material 1 & material 2
Output Material 1
Pre Post D1 D2
Material 2
D3
D4
Material 3
D5
D6
Produce form manufacturer 1
D7
D9
material 2 & Produce form material 3 manufacturer 2
D8
D10
material 1,2,3
D11 D12
Produce final manufacturer
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Table 2. (continued) P7 P8 P9 Event E1 E2,E3 E4 ….. D D1 …. D7 D14 ….
Distribution
Distribution Final productPrepare for D13 center warehouses Storing in Warehouse Warehouse 1 Prepare for Store in D15 1 warehouse 1 warhouse1 Storing in Warehouse Warehouse 2 Prepare for Store in warehouse D16 2 warehouse 2 2 Description Resource Pre. Receiving bill of order material 1 form Null semi-finished product manufacturer 1 Are similar to E1 … Material 1 is produce by manufacturer 1 Input E1
Output P1
Rule Flow
E4,E5 P7
P4 E10,E11
and xor
D14 D17 D18 Post. D1
D7
3.6 Arena Model and Simulation Results Based on the supply chain model shown in Figure 5 and information from Table 2 with a more details, a sub-model was simulated in Arena 10 by eliminating the retailers. As shown in the proposed sub-model illustrated in Figure 2, each of the
Fig. 5. The simulated sub-model
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manufacturers can procure their materials from the suppliers 1, 2 and 3 and after producing the final product, send them to the distribution centers. Distribution centers decide about the distribution of the products to the warehouses based on a 50% 2-way by chance decision type. The simulation was designed run the replication for 500 times within 720 days before giving the results. Some of the results of the simulation related to entities (time), and process have been illustrated in Figure 6,7. Figures illustrate the process related to suppliers, manufacturers, distributors and warehouses. Our objective is not to show the key performance indicators (KPI) and optimization of the model but to show the possibility of using the information in simulation and analyzing them to have the results.
Fig. 6. The process result-time per entity
Fig. 7. The accumulated time result
4 Conclusion Business process modeling (BPM) provides management with a static structured approach to business improvement, providing a means of documenting the business processes, and business-process simulation (BPS) allows management to study the dynamics of the business. In the context of business process change BPS can be helpful. Thus BPM and BPS help to facilitate process thinking.This paper provides a
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preliminary analysis only and more findings with details will be presented in future reports. However, despite the preliminary analysis provided in this paper, it has numerous findings and contributions. First, it illustrated that grammar-based process modeling can be used with business process simulation to improve the transparency of the system description and its process details. Moreover, since the modeling and simulating the processes include modeling the inputs, outputs, resources, workflow, etc, using a grammar-based modeling can bring about more flexibility of the supply chain dynamic simulation. Besides, a dynamic environment like supply chain includes its specific mechanisms and rules. Because these rules can be represented grammatically, therefore, in order to simulate a rule-based supply chain, the approach presented in this paper can be useful.
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