Object-Oriented Simulation for Service Supply Chain

Object-Oriented Simulation for Service Supply Chain Jong-Hyuk Moon and Young Hae Lee* Department of Industrial and Management Engineering Hanyang University, S. Korea [email protected], [email protected]

Abstract. Most existing supply chain research focuses exclusively on the manufacturing sector. However, there is a lack of research on the service sector, which is becoming increasingly important in the global economy. In addition, it is harder to design a conceptual simulation model than a manufacture supply chain does to the diversity of structures in the service sector. In this paper, we develop a service supply chain simulation models, based on object-oriented approach using UML analysis/design tools and ARENA® simulation language. We use a conceptual model of simulation because of its diversity and changeability. Objective-oriented modeling has demonstrated an effective simulation design and the practical process. The two main features of the proposed procedure are the definition of a systematic conceptual procedure to design service supply chain models and of a set of rules for the conceptual model translation in an ARENA® simulation language. The goal of this research is to improve the knowledge on service supply chain management with the developed model and support the simulation model development on service supply chain efficient. Keywords: Service supply chain management, Objective-oriented, Simulation.

1

Introduction

The expansion of service industries in the world economy has already surpassed the manufacturing industry in developed country. However, the existing supply chain management literature has been focused on the manufacturing industry applicable and has limited application to service industries. Korea’s mobile manufacturing industry has had great success in the early 21st century. But manufacturing-centered mobile phone industry is difficult that can lead to continued success in the current corporate environment. Korea’s cell phone company had struggled for the market to move to smartphones. Because, the previous market has be competed in performance of product but now mobile industry requires quality of products and services, innovation. The study of supply chain service is made more difficult by the lack of a formal logical structure. Design a standardized model of service supply chain results from a *

Corresponding author.

J.-H. Kim et al. (Eds.): AsiaSim2011, PICT 4, pp. 268–280, 2012. © Springer Japan 2012

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variety of service systems. Therefore, the first step of the study of supply chain service is to include a variety of service systems. According to previous studies of service were targeted as a single service system. However, the service industry also has a complex supply chain structure similar to manufacturing industries. Therefore, research must be worked in terms of the supply chain rather than only considering a single service system. Service supply chain and manufacturing supply chain are part of a very small share in many parts. In particular, the service characteristics of accounted for in Manufacturing supply chain is models that describe inventory / replenishment. In this paper, we develop a service supply chain logical structure and simulation models, based on an object-oriented approach. Service supply chain takes advantage of programming an objective-oriented model to build up a conceptual model of simulation because of its diversity and changeability. Objective-oriented modeling has demonstrated an effective simulation design and the practical process. Especially, it is based on the UML analysis/design tools and on the ARENA® simulation language. The main contributions of this paper exist in three areas: 1) Conceptual model of service supply chain defines for development of simulation, 2) Logical structure of service supply chain simulation model is based on object-oriented approach, 3) We propose to design a simulation model of service supply chain by using ARENA® simulation language. This paper is organized as follows. The service supply chain deals with literature in section 2. In section 3, service supply chain explains conceptual model. In section 4, general model of the service supply chain explains procedure and implementation. In section 5, general model of the service supply chain is applied to the tourism sector, followed by the conclusions and insights in section 6.

2

Literature Review

2.1

Service Supply Chain

The characteristics of services: intangibility, perishability, simultaneity, heterogeneity and customer participation. These characteristics of service make it difficult to develop the general framework that is about the structure of service supply chain. However, there have been some attempts. Armistead and Clark (1993) have applied to the service supply chain through the concept of the value chain. Ellram et al. (2004) proposed service supply chain framework that is included the process of managing and coordinating in the service industry from the first supplier to the final customer. Zhang et al. (2009) developed service supply chain conceptual model based on business process. His conceptual model is composed service providers, service integrators and consumer's demand. Another challenge to building a framework is that unlike manufacturing, service supply chain does not have a standardized Performance evaluation of rating scale. Ahn and Lee (2010) developed service supply chain’s performance measure framework using Fuzzy-AHP.

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Although earlier researches have made a contribution of concept of the service supply chain, such studies have failed to provide a formal model. For example, they cannot precisely define and the role of the elements in service supply chain. 2.2

Supply Chain Simulation

Supply chain Simulation is a dynamic model combining the characteristics of the quantitative, mathematical and computer model. Although simulation has mathematical characteristics, the mathematical model with closed form does not provide the solution. The main area of simulation studies are as follows: Spreadsheet simulation is very easy to use and popular. Sounderpandian (1989) implemented MRP using Spreadsheet simulation. Towill (2003) studied the VMI (vendor managed inventory) model in supply chain using this methodology. System dynamics (SD) was used to demonstrate the bullwhip effect in supply chain. Forrester (1961) classified supply chain that is constructed retailer, wholesaler, distributor and factory. This study analyzed the reactions in a link to each area of supply chain. Forrester (1961) explained through experimental variation of the sensitivity of customer demand. After which Lee et al. (1997) by the amplification of these fluctuations defined bullwhip effect. Higuchi and Troutt (2004) studied the Tamagotchi's supply chain by using system dynamics. The most widely used simulation methodology in the supply chain is discrete event simulation. This method is most appropriate to express the dynamic supply chain system. Vollmann et al. (1997) was making researches MRP, ERP in the lower part of the supply chain system. Object-oriented simulation has proven to be powerful techniques which are reusability and scalability. Rossetti and Chan (2003) studied the supply chain simulation framework by using object-oriented approach. This study established a manufacturing-oriented supply chain based on object-oriented conceptual model. Alfieri and Brandimarte (1997) modeled the supply chain logistics network through object-oriented techniques.

3

Object-Oriented Simulation Model for Service Supply Chain

3.1

Service Supply Chain Structure

The most important part of simulation design is from the physical environment to the process of converting of a conceptual model. Conceptual model design of the study is the first step of the simulation and it is the most influential in all phases. This research proposes service supply chain structure. The structure is to include the wide range of services supply chain system. Service supply chain simulation consists of the four modules which are Customer module, Service Agent module, Service Operator module and Service Provider module. Demand module represents the information of customer demand and customers receive the ordered services. Customers can choose the type of service, or be selected in consideration of their state and environmental. For example, customers can choose

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the tour package in tourism service but in case of hospital and product service center, they are being received in consideration of consumers' health status or condition of the product. Service agent module checks service capacity according to the customer’s service order and it distributes the optimal allocation of service activities. Service operator module is responsible for the design of the service activities to respond to the needs of customers. For example, service operator role is to design a tour package in tourism service and assigns service resource to each service activity. Service provider module supplies to provide services service activity with service resource. Each area of the object of the service supply chain can use to design simulation’s conceptual model. Service supply chain simulation framework is shown in Figure 1. 3.2

Procedure for Developing Simulation Model

In this study, in order to develop the simulation model uses object-oriented methodology. Object-oriented methodology reduces the complexity of simulation modeling by scalability and reusability. This study is based on the UML analysis/design tools and on the ARENA® simulation language. ARENA® simulation package has been made by the SIMAN language, it express feature of animation, input and output analysis in GUI(graphical user interface) environment. UML(unified modeling language) take the blueprint to develop simulation model in various types of software (Booch G. et al., 1999). UML diagram has Class diagrams, object diagrams, use case diagrams, sequence diagrams, etc. UML express each module of the object definitions, parameters, operations in object-oriented service supply chain simulation model. The two main features of the proposed procedure are the definition of a systematic conceptual procedure to design service supply chain models and of a set of rules for the conceptual model translation in an ARENA® simulation language. The following is a simulation model development process.

Fig. 1. Service supply chain simulation framework

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The first step is the design of functional model. The purpose of this step is the analysis phase of service supply chain modules for UML conceptual modeling phase of the simulation. The design phase functional model represents UML use case diagram through the definition of a component. In other words, this phase analyzes role of demand for service, service agent, service operator and service provider, defines message exchange procedure between each module. The second step is the design of dynamic model. The purpose of this step is the interaction of components for the messages and actions represents through the UML sequence diagram. Messages sent from one object to another object means to move the lifeline of one object to another object's lifeline in a sequence diagram. The third step is the design of object model. In this step, the components inside the structure and the relationship through the UML class diagram collect the appropriate class group. The Class diagram is clearly the internal structure of the object that defines each object's name and attributes, relationships with other objects. The last step is the implementation of the general model by UML and ARENA®. This step classifies to express UML classes in classes used in the simulation package ARENA®.

4

General Model for Service Supply Chain

The diversity and complexity of supply chain services makes it difficult to define a general model. However, the definition of a general model is necessary. General model of the service supply chain simulation gives an outline of the basic components and features. 4.1

Functional Model

In general, functional model shows the flow of information within the system. The Internal flow of information relates to resources, targets, and activity. The objective of this phase expresses abstraction of system components through the use case diagram. The use case diagram gathers system's functional requirements. The use case diagram is hierarchically organized so that system's functional requirements represent phase of the abstract level (upper level). This use case diagram provides the basis of design and development. As a result, this step is an important step that reflects the perspective of developers in the areas of applied simulation. Figure 2 shows a use case diagram of the service supply chain. In Figure 2, Service Supply Chain System Actors are customer, Service agent, Service operator and Service provider, system use case is Service Demand, Service Type, Service Processes, Service Procedure, Service Activity, Service Resource and Resource. Of these, Service Procedure, Resource is expanded use case of Service Processes and Service Resource.

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Fig. 2. Services of the supply chain use case diagram

4.2

Dynamic Model

The use case diagram explains service supply chain components and their relationships. The dynamic model can explain the components of each area in service supply through the sequence diagram (Roff, 2003). The message is passed to an object from an actor and this diagram shows system control flow. The sequence diagram represents the interactions between instances of the class and it shows in detail the flow of processing. Thus, a sequential diagram represents all possible paths or single path. Figure 3 shows a sequential diagram of the service supply chain.

Fig. 3. Services of the supply chain sequential diagram

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Object Model

In this step, Depending on the simulation software, developers should consider the type of class related to software. It is important that defines the relationship between classes corresponding to the software. Object model design is based on analysis of the following three categories: The class identification: Class definition depends on the considerations of each developer. There is no standard method for finding all the classes in a system. In this study, the definition of the class proposes to find through the use case diagram. The class relationship identification: Defining relationships between classes make easy model generalization that reduces complexity of the actual implementation of the simulation. The class structure identification: Attribute and operation for each class define through functional model and dynamic model. Attribute is defined by use case diagram, operation is defined by sequence diagram. Figure 4 shows four areas of supply chain services for the class diagram. Four areas of module classes represent the operations and attribute in service the supply chain.

Fig. 4. Conceptual model of supply chain services

ARENA® consists of two structures, one is the EXPERIMENT(static structure), and another one is MODEL (dynamic structure) . ELEMENTS panel is a tool of the EXPERIMENT, BLOCK panel is the process of running the tool by taking the information of ELEMENTS. In this study, the general model of the service supply chain uses the template of the ARENA. The object class of the static structure uses ELEMENTS panel, and dynamic structure uses BLOCK panel and another panel. ARENA® mapping table for converting shown in Table 1.

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Table 1. ARENA mapping table Template Panel

ARENA Class Customer Demand

ELEMENTS Template Panel

BLOCK Template Panel

Advanced Transfer Template Panel

Entities Expressions Attributes Resources Sequences Stations Create Assign Route Dispose Size Delay Release Stations

Modules Class Service Service Agent Operator

Service Provider

● ● ●

● ● ● ● ●

● ● ● ● ● ● ● ●

Based on this table, General model of service supply chain modules expresses class diagram in UML taking into ARENA® Templates. Simulation of the general model is shown in Figure 5. Its aim is to converts for ARENA simulation model. In this UML class diagram, customer demand module uses Entities, Expressions, Attributes in ELEMENTS template, and Create, Assign and Dispose in BLOCK template. Entities generates an event in the simulation model. Demand information of the object is expressed in the Expressions module. Attributes module defines variable property of object.

Fig. 5. General model of service supply chain simulation

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Service agent module uses Attributes, Sequences and Stations in ELEMENTS template, and Stations and Sequences in BLOCK template. Service operator uses Expressions, Route, Station. Service provider uses Resources in ELEMENTS template, and Create, Size, Delay, Release in BLOCK template. Information exchange between classes is shown in Table 2. Table 2. Information exchange class

5

Customer Demand - Service Agent

Modules Class Service Agent Service Operator

Service Operator Service Provider

Information Sharing Class

Customer Index

Order Type

Service Activity

Related ARENA Class

Assign Expressions Element

Sequences

Station Route

Applying to Tourism Services Supply Chain

Tourism service is one of service industry that includes hotel, passenger transport and sightseeing. Service supply consists of various service components in a value service network. Zhang Ying-zi [10] proposed that tourism serve supply chain is a bundle of tourism service product which is oriented to tourists and is based on the order of travel agents arrangement and uninterrupted time. However, most research on the service sector is focused on marketing. Sinclair and Stabler(1997) emphasized the importance of the tourism industry in terms of the supply chain. Page (2003) proposed that supply chain has to be the premise in the tourism industry. 5.1

The Structure of Tourism Services Supply Chain Simulation Model

Tourism service supply chain consists of customer, travel agent, tour operator, service provider on the basis of developed general model in this study. 5.2

Conceptual Model

In this study, the conceptual model of tourism services supply chain is based on a general model presented in section 4. Figure 6 is a conceptual model of tourism supply chain services describes how the demand module generates an event and gives unique characteristics to each customer. This model shows the flow where the Tour agent module confirms customer order and allocates is the travel package process. Tour operator module allocates the service activities to customer. Service provider module supplies service resources.

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Fig. 6. Conceptual model of tourism services supply chain

5.3

Implementation Using ARENA®

Tourism services supply chain consists of six travel package for implement of ARENA®. The process for each travel package is shown in Table 3. Customer's arrival time interval considers expo (6.5) and expo (10). Warm-up period is 2000 hours (EXPO(6.5)), 1000 hours(EXPO(10)). Travel customers to choose the ratio is 13%( Package 1), 12%( Package 2), 10%( Package 3), 20%( Package 4), 23%( Package 5) and 22%( Package 6). Moving time of customer was not considered. Simulation length is 365 days, and repetition is five times. Resources and processing time for each service activities are shown in Table 4. Table 3. Travel Packages process Tour Type Package 1 Package 2 Package 3 Package 4 Package 5 Package 6

Sight 1 Sight 2 Sight 1 Sight 4 Sight 6 Sight 3

Sight 2 Sight 3 Sight 2 Sight 5 Sight 5 Sight 4

Plan Sight 3 End of Tour Sight 4 Sight 6 Sight 1 Sight 5

Sight 4

End of Tour

End of Tour End of Tour End of Tour Sight 6

End of Tour

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J.-H. Moon and Y. Hae Lee Table 4. Resources and processing time for each service activities Type

Resource

Processing Time

Sight 1

Sight 3 Sight 4 Transpor- TransporHotel 1 Hotel 2 tation 3 tation 4 Transpor- Transpor- Restaurant Excursion 1 tation 1 tation 2 3 Restaurant Restaurant Hotel 3 1 2

48

Sight 2

24

36

12

Sight 5

Sight 6

Hotel 5

Hotel 4

Transportation 5 Excursion 2 Restaurant 4

Restaurant 3 Excursion 3 Restaurant 5

24

36

Fig. 7. Object-oriented simulation model of tourism service supply chain in ARENA

Figure 7 is tourism services supply chain simulation model by object-oriented in ARENA environment. 5.4

Experimental Results

Service supply chain simulation model compare results of expo(6.5) with results of expo(10) for model validation. Customer demand’s customer data, service agent's service process data, service operator’s activity data, provider's resource utilization of the Factor analysis according to changes in demand factors do not affect each output data. In addition, the validation of simulation model is that it only generates one of the objects and traces the flow of an object.

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Conclusion

Until now, the service industry has been primarily studied in the fields of management such as marketing. Supply chain simulation research has focused on manufacturing supply chain. Recently, service industry is being important day by day, and service system is made up supply chain. The purpose of this study develops service supply chain simulation model by object-oriented under the ambiguous conceptual model of service supply chain. This research progress defines the property and structure of service supply chain and then, simulation model implement in ARENA®. The result of study, first, structure of service supply chain was defined for development of simulation, and the role of each module in service supply chain was proposed. Second, this study propose general service supply chain model using objet-oriented programming for development of service supply chain simulation model. This general model can apply the future research for service industry. Finally, this study proposes to design simulation model based on object-oriented in ARENA®. In future research, we will develop a hybrid model that uses mathematical optimization and simulation models are mixed. Acknowledgment. This research was supported by Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education, Science and Technology (2011-0002993).

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