Supply chain system taxonomy: development and application Charu Chandra, Armen Tumanyan Department of Industrial and Manufacturing Systems Engineering University Of Michigan – Dearborn 4901 Evergreen Road, Dearborn, MI 48128, USA Abstract Supply chain management deals with problems that are interrelated to each other. Their modeling and analysis requires use of common data, which may be part of different, sometimes heterogeneous information systems. Decision-making tools need mechanisms for accessing these data, retrieving knowledge about a particular problem, and creating models for solving them. System taxonomy offers classification of these problems, their relationships, and characteristics through multidisciplinary analysis of supply chain (SC) activities and attributes. It can serve as a meta-model for problem model development. These models incorporate knowledge about different problems in supply chain system. This paper makes the case for use of taxonomy as a technique for SC problem classification by offering a framework and illustrating its development through systematic representations. Keywords Supply Chain Taxonomy, Supply Chain Classification, Supply Chain Management, Information Modeling 1. Introduction In a rapidly changing environment, information system is the key to managing any system, especially complex systems, such as a SC. Information organization for SC is a challenging task because of its distributed structure. Besides, SC members are distinct organizations with their own information systems, mostly incompatible with each other. A unified approach is required to integrate these different systems. Shared vocabulary and unified information representation can be useful for this integration. This paper proposes a framework based on these traits for integrating decision-making components. This will enable compatibility of different software tools and adaptability of the entire system to the changing environment corresponding to (a) SC structure and configuration, and (b) SC member’s information system architecture. This paper is organized as follows. First, SC system taxonomy overview presents the overall approach of taxonomy development and its application. The next section describes how taxonomy can be used for information structuring in various fields. A framework for taxonomy development and application components is described. It consists of an information-modeling environment starting from highly generalized system representation, SC domain system taxonomy development, and generic and specific problem model taxonomy building. The last section describes a step-by-step implementation of proposed framework with examples of the four level taxonomy development approach. 2. Supply chain system taxonomy: an overview SC system taxonomy aims to provide a multidisciplinary representation of SC activities and characteristics. It consists of information collection, systematic analysis, and classification of system attributes. Taxonomy is a systematic representation of a system’s existence. Accordingly, taxonomy is built based on principles of system theory. It is a mechanism for structuring the knowledge about a certain domain. System taxonomy is organized for the entire system. SC is an organization, whose components are interrelated to each other. This cohesion makes the system unmanageable, if it is considered as one unbreakable unit. System taxonomy provides mechanisms for dividing SC system into relatively independent units, providing as minimal a coupling between units as possible. Further, iterative decomposition can build a robust hierarchy of describing system characteristics. SC system taxonomy is designed to represent SC characteristics in the form of meta-meta model. This is a very abstract and problem independent representation of the system. SC system taxonomy application encompasses problem model taxonomy development, which incorporates all characteristics with their relationships for a particular problem. The problem model taxonomy is problem dependent and is built embedded in the structure and vocabulary of system taxonomy. Problem solving tools need data models to operate with. Ontological commitments provide connection with variables and contain constraints and rules applied to these variables. A discussion of ontology is out of scope of this paper. It is, however, presented to complete the picture of information modeling environment. Conference Proceedings, 12th Annual Industrial Engineering Research Conference (IERC 2003), Portland, Oregon, May 17 - 21, 2003. 3. Taxonomy in Sciences Taxonomic classification systems have traditionally been designed for structuring the body of knowledge. Logically, taxonomy is mainly motivated by two objectives : 1. To introduce structure into a body of facts. 2. To build a unified and homogeneous view of the domain of interest. Designers of taxonomic classification have followed three principles: system should be 1) organic, 2) simple to grasp, and 3) easy to memorize. Taxonomy originally was developed as a tool for classifying biological organisms. In biology, the assumption is that more homologies two organisms share, closer they must be in terms of evolutionary distance . Taxonomy as a tool is applied for information conceptualization, organization, and structuring; not only in biological science, but also in Chemistry, Organizational Science, Manufacturing Systems, and many other fields of study. One of the fundamental problems of integrating manufacturing enterprises is the lack of theoretical basis. In other engineering disciplines there is always some basic theory to work with, in order to provide insight and conceptual framework. For example, electrical engineers have Ohm’s law and other circuit theorems, and mechanical engineers have Hook’s law, theories of bending, motion and so on. In manufacturing, we have Frederic Taylor’s precepts . The purpose of this paper is to provide theoretical foundation for information organization in a SC. Taxonomy is utilized as the basis for classification and structuring of information in the SC. Taxonomy enhances knowledge and understanding for predicting or controlling manufacturing system behavior . Taxonomy deals with complexity of information by building hierarchical structure of data, wherein any characteristic can be found, used, and updated easily. 4. The Framework Development In the current research methodology for information system design, domain information modeling starts directly from problem identification and then inside the problem, taxonomies of terms and definitions are created , . These approaches are good for stand-alone domain representations (conceptually closed systems). But systems are usually not closed. The isolation from surrounding environment can jeopardize the correctness of information that models are designed to represent. To bridge this deficiency, this paper proposes a novel approach for building an additional layer in information modeling environment for SC: the system taxonomy. It considers SC as a complex system in whole, which contains parts. SC is also a managerial system. In elaborating the framework, SC system features are described in sufficient details. An overall framework for system taxonomy development and application is depicted in Figure 1. General System Observation General System Taxonomy Supply Chain System Observation System Application Taxonomy Specialization ApplIcatIon Specialization Supply Chain Configuration Problem Observation Generic Problem Taxonomy Specialization Supply Chain Production Planning Problem Observation Problem Domain Taxonomy Ontological commitments Repository Retrieving/Storing Data Knowledge Model Knowledge Object model for application Figure 1. Supply chain system taxonomy development and application framework The significance of system approach is that, while all possible aspects of the problem are discussed, only those relevant to the problem are taken into account in decision-making models. General system taxonomy provides high level clustering of characteristics, describing a system. Conference Proceedings, 12th Annual Industrial Engineering Research Conference (IERC 2003), Portland, Oregon, May 17 - 21, 2003. General system stands for a set of things and relationship among these things. Formally, we have S = (T, R) (1), where S,T,R, denote a system, set of things T distinguished within domain S, and relation (or relations) R defined on T, respectively. Thing consists of seven components: T ( I ,O, E , A, F ,M , P ) (2), which are: input, output, environment, agent, function, mechanism, and process respectively. These components of generic system are described below in Table 1 : Input Output Environment Agent Function Mechanism Process Table 1. Seven system components Physical item, information, or service that is necessary to start processes. Physical item, information, or service that result from processing of input. The output is related to the total accomplishment of the function. Physical or sociological factors, within which system elements operate. It relates to resource requirements, both physical and human. Computational or human resources for carrying process. Mission, aim, purpose, or primary concern of the system. Physical or logical facilitators in the generation of an output. Flows, transformations, conversions, or order of steps, which transforms an input into an output. Application taxonomy is a specialization of generic system taxonomy as applied to a SC domain. In SC, four main stages can be distinguished: supply, production, distribution, and consumption, as depicted in Figure 2. The proposed framework considers these as sub-systems, with corresponding seven system components. These system components constitute the wholeness of any system that needs to be investigated. The wholeness is important in analysis stage, but during the design stage only a few components are incorporated into a problem representation, that is those relevant to the problem. Supplier 1 Retailer 1 Raw Material vendor 1 Distribution center 1 Supplier 2 Plant 1 Vendors Retailer 2 Distribution center 2 Supplier 3 Plant 2 Raw Material vendor 2 Retailer 3 Distribution center 3 Supplier 4 Supply stage Customers Retailer 4 Production stage Distribution stage Consumption stage Figure 2. Supply chain system network The seven system components of a SC constitute the upper level of application taxonomy hierarchy and represent the higher level of abstraction in SC information modeling. Iterative decomposition of these brings out more details into the information capturing and representation environment. Sub-components are organized in the form of objects and their groupings through systematic analysis of SC processes and activities. For system taxonomy design, four corollaries are adopted from . Objects or their groupings identification must meet corollary 1: standardization, thereby providing component reusability. Objects are designed not for one particular problem, but from a system perspective, starting from general purpose to more specific purpose, thus corresponding to corollary 2: one component – one purpose. Object groupings are decomposed into small components (sub-groupings or objects) to meet corollary 3: large number of small components instead of few big components. Thus, by separating the information content, the system is made manageable, thereby, satisfying corollary 4: Uncoupled design with less information content. While general relations are defined for a system, conceptual relations are defined for a certain domain. Domain can be defined as a structure (T, W) , where T is the set of things in a domain; W is a set of maximal states of this Conference Proceedings, 12th Annual Industrial Engineering Research Conference (IERC 2003), Portland, Oregon, May 17 - 21, 2003. domain (possible worlds). In other words, W is a collection of all possible instances (objects and their groupings) of a domain. For SC, W is a set of all possible combinations of SC system things. Accordingly, SC system can be represented as a collection of all possible states, with appropriate relationships S (T , W, R) (3). A generic problem taxonomy is a class of problems that can occur in SC. Every problem taxonomy, either generic or specific, must contain information about the following issues: problem description, objectives, strategies, data model, rules pertinent to the problem, methods and approaches for dealing with the problem, and degree of adaptability. Generic problem taxonomy can be derived from application taxonomy by specializing it to a problem, which still can be of a general type. For each possible system instance wW , the intended structure of w according to S is the structure: Sw (Tw , R w ) (4), where Tw is an instance of system things, Rw is the set of extensions (relative to w) of elements of R: R Rw |wW (5). S denotes the set of all “intended world” structures of system, S S w|wW (6). Sw as an instance of the system represents one SC problem and w is all possible states of this particular subsystem. Configuration problem class is concerned with structuring and/or restructuring the network of SC to achieve a specific goal, or a set of goals. Configuration problem adopts from SC system taxonomy the structure and those characteristics and features, which are relevant to this particular problem Sw . Problem domain taxonomy can be built for various issues of a generic problem. Scheduling is one such issue. Taxonomy for this level captures from its upper level, information model general features and through domain observation builds a specific information model that incorporates characteristics involved in solving this specific issue. The last stage in the proposed information-modeling framework is knowledge model building. This is related to Ontology development. Problem solving tools require models (M) to operate with. M ( Sw , I) (7). I are translators (software programs), which connect variables V from data storage to system things T, through observation channel Bw , and represent it in a knowledge representation format (KRF), I (V TwBw ) (8). Translators are especially useful when system has a distributed architecture, and data are stored in heterogeneous platforms. KRF is a format that should be understandable by all system users. Ontology can be presented as continuation of problem representation by adding new features to it. O ( M , A) (9). Constraints are defined for decision modeling for a problem and represented using variables identified for the purpose. A(CV BC ) (10), where A is a set of axioms representing constraints C with variables V, through observation channel BC , Taxonomy development and application framework constitutes the information-modeling environment. Different taxonomy levels represent different levels of abstraction in information representation, from where information or knowledge can be captured and ontology built for it, thus formulating the knowledge for the desired abstraction level. 5. System taxonomy development 5.1 Supply chain domain taxonomy A generic taxonomy structure is applied to each stage in SC organization: supply, production, distribution, and consumption. A common template for information structuring (taxonomy) can be applied to each of the four systems representing these stages. This section presents taxonomy only for production system. Other system components can be similarly represented. SC domain brings specialization to generic structure by incorporating features and issues from SC domain. Object-oriented (O-O) modeling and unified modeling language (UML) provide tools and methodology for deploying taxonomies. A fragment of SC domain application taxonomy in UML diagram is depicted in Figure 3. Application taxonomy is not specific to one SC subsystem. It is general enough to be applied to any component. The seven components of a system are related to SC system class with composition type of relationships. Associations relate subclasses to upper level components. Detailed elaborations of each of these components in turn reveal new classifications described in . This paper is concerned with tying SC domain system taxonomy with the problem representation environment. In SC system taxonomy, problems are formulated mainly at strategic, tactical, and operational levels . Operational or technical system is involved with the actual task performance in an organization such as, production and distribution of products or services. It is involved not only in technical work, but also knowledge utilization. The second level, the tactical or organizational, coordinates and integrates the task Conference Proceedings, 12th Annual Industrial Engineering Research Conference (IERC 2003), Portland, Oregon, May 17 - 21, 2003. performance of the technical system. MRP and capacity planning can be considered as this class of problems. The strategic or institutional level is involved in relating activities of the organization to its environmental system. These are long term planning issues involving investments (fixed costs) decisions for the strategic planning horizon. The management system spans the entire organization by directing technologies, organizing people and other resources, and relating the organization to its environment. Fu n c tio n s Flo w s Pro c e s s e s -Product:Integer -Information:Integer -Material:Integer -Order:Integer -Financial:Integer -Transformation:Integer En viro n m e n t -Means:Integer -Goals:Integer I n pu t -Resources:Integer -Information:Integer -Materials:Integer O u tpu t S u pply C h ain S ys te m -Constraints:Integer -OrganizationalBehaviour:Integer -Market:Integer -Services:Integer -Products:Integer Me c h an is m s Man ag e m e n t -Strategies:Integer -Structures:Integer -Decisions:Integer -Strategic:Integer -Tactical:Integer -Operational:Integer Pro du c tio n U n it -Resources:Integer -Attributes:Integer Ag e n ts -Transportation:Integer -Warehouses:Integer Figure 3. Application taxonomy fragment 5.2 Supply chain generic and domain problem taxonomies Splitting problem representation modeling into two parts provides the means for developing templates that can be applied to specific situations. Templates correspond to Generic problem taxonomies. Concrete applications can use information models provided by domain problem taxonomies. An example of configuration problem is illustrated as a generic problem, and scheduling issue in configuration problem is taken as an example of a specific problem. SC Configuration problem can be projected from SC domain taxonomy as a collection of four subsystems: supply, production, distribution, and consumption. For illustrative purposes, only production system is demonstrated with corresponding characteristics (Figure 4). Similar diagrams can be drawn for other three components of SC system. I n pu t O u tpu t -Products:Integer Fu n c tio n s Minimize lead time Reduce inventory Maximize utilixation -Resources:Integer -Information:Integer -Materials:Integer En viro n me n t Ag e n ts Su pply Ch ain Sys te m Me c h an is ms Stru c tu re s -Structures:Integer -BOM:Integer Flo w s Man ag e me n t Strate g ie s -ResourceType:Integer -BatchSize:Integer -BatchType:Integer -ManufacturingOrientation:Integer -Operational:Integer Pro c e s s e s -Transformation:Integer Pro du c tio n U n it -Product:Integer -Information:Integer -Resources:Integer -Material:Integer -Attributes:Integer -Order:Integer -Financial:Integer Sc h e du lin g MRP Figure 4. Configuration generic problem – Production system UML diagram Scheduling is chosen as a specific issue for which domain problem taxonomy is demonstrated. For providing information model for this problem, four stages of supply chain are included. However, for illustration, only the Conference Proceedings, 12th Annual Industrial Engineering Research Conference (IERC 2003), Portland, Oregon, May 17 - 21, 2003. production stage is depicted in Figure 5. Scheduling issue is concerned with distribution of products among resources in a way so as to achieve maximum resource utilization, minimize lead time for production, and maximize throughput. Figure 5 depicts characteristics involved in this problem that have to be processed by decision-making tools. Su pply Ch ain Produ c tion Plan n in g Proble m Produ c tion Un it -ID:Integer Age n ts Produ c t Tran sportation Re sou rc e -DateOfTransportation:Integer -DateOfDelivery:Integer -Name:Integer -Destination:Integer -Shifts:Integer -Type:Integer -NumberOfHours:Integer -TransportationCost:Integer -Capacity:Integer -TransportationTime:Integer -FixedCost:Integer -DeliveryTime:Integer Re sou rc e Attribu te s Produ c tion -ResourceName:Integer -ProcessingCost:Integer -Defectiveness:Integer -SetupCost:Integer -BreakdownFrequency:Integer -BreakdownDuration:Integer -SetupTime:Integer O u tpu t -PartStatus:Integer -PartType:Integer -Weight:Integer -Size:Integer -InventoryHoldingCost:Integer De man d -Data:Integer -QuantityNet:Integer -QuantityShipped:Integer -PremiumTrend:Integer -Yield:Integer -Part:Integer Figure 5. Information model for scheduling problem 6. Conclusion This paper proposes a novel approach for knowledge organization for SC problem management. Using taxonomy methodology, the article presents a framework of the supply chain system. Each layer stands at different abstract level and serves as the template for the lower level models. The ranking of four levels is: generic system taxonomy, application taxonomy, generic problem model taxonomy, and domain problem model taxonomy. The paper discusses the overall approach of taxonomy development, its application and how taxonomy can be used for information structuring in various fields and gives four taxonomy development examples to illustrate the implementation procedure of the proposed framework. Acknowledgement This research is funded by grants form the University of Michigan-Dearborn under the Research Excellence and Economic Development Fund project, and by Ford Motor Company through the University Research Program. References 1. McCarthy, I., Keith, R. (2000). "Cladistics: a Taxonomy for manufacturing organizations." Integrated Manufacturing Systems 11(1), 16-29 2. 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