یکپارچه سازی پایداری در درون انتخاب تامین کننده با روش شناسی سیستم خاکستری و مجموعه ناهموار

Supplier selection plays an important role in the management of a supply chain. Recent emphasis on sustainability has made this selection more complex. Decision support tools and methodologies can help organizations and supply chain managers make more effective decisions. Many tools have been developed with a variety of formal modeling techniques. These techniques may be limited for a variety of reasons. To help advance this area of research and to help further integrate sustainability discussion into the supplier selection modeling area, we expand on a novel approach first introduced by (Li et al., 2008). This approach utilizes grey system and rough set theory. Our expansion and contribution includes introduction of additional levels of analysis and application of this methodology, the explicit consideration of sustainability attributes, and insights into the technique with some sensitivity analysis. Implications of the methodology and future research directions, further expanding the methodology and its applications, conclude the paper.

Organizations with complex decisions typically have numerous factors to consider and evaluate in the management of suppliers and supply chains. Eventually managing these suppliers requires a careful balance when seeking to procure supplier services or products. Supplier selection and management can be applied to a variety of suppliers throughout a product's life cycle from initial raw material acquisition to end-of-life service providers. Thus, the breadth and diversity of suppliers makes the process even more cumbersome. As has also been evidenced in the research literature the evaluation of suppliers requires consideration of both tangible and intangible factors (Sarkis and Talluri, 2002). Many times these factors, whether tangible or intangible, are not always very clearly defined. A significant amount of judgment and ‘grey’ area is involved in the evaluation scheme. Within supply chain management the supplier selection decision is one of the critical issues faced by operations and purchasing managers to help organizations maintain a strategically competitive position (Chen et al., 2006). Globalization, outsourcing and offshoring have added to this competitive burden where selection of suppliers has become an even more critical partnering issue. Suppliers are needed to furnish organizations with the necessary products, components, and materials in a timely and effective manner to help maintain a competitive advantage. Commodity and price-based supplier relationships are no longer acceptable for suppliers of critical materials or for organizations that seek to introduce innovative supply chain management issues, especially those that focus on social and environmental concerns (sustainability). These strategic and sustainability factors play a vital role for the long-term resiliency of a supply chain (Seuring and Müller, 2008; Ciliberti et al., 2008; Zhu et al., 2008). Given this rise in managerial and organizational importance, strategic management of suppliers becomes important and a strategic decision model that allows inputs from a variety of managerial functional areas and multiple factor dimensions proves beneficial to management. Also, historical performance of the suppliers and the previous decisions related to these suppliers are critical information that has not been effectively integrated into decision models. The sustainability factors utilized within our model will integrate the ‘triple-bottom-line’ selection factors that include economic/business, environmental and social factors (Robins, 2006). We also provide insights into the evaluation to identify and compare which selections are made when only economic factors versus a complete set of sustainability factors are used for evaluation purposes. Given that strategic decisions in organizations need to incorporate tangible and intangible factors into any analysis that seeks to identify and select critical supply chain partners, more advanced techniques can provide insights (Sarkis and Talluri, 2002). One such toolset integrates grey system theory and rough set theory methodologies (Li et al., 2007; Li et al., 2008). Grey system theory is a generalized form of fuzzy approaches and mathematics. Rough set methodology and theory utilizes set theory to help filter and focus the set of acceptable suppliers and factors in their evaluation. Together these two techniques provide complementary avenues to rank or select preferred organizational suppliers, based concurrently on management/expert opinion and previous supplier performance and decisions. We seek to further develop and apply this tool to help organizations arrive at sustainability focused decisions with respect to supplier selection. This paper advances the use of Grey system and Rough set theory as an effective and realistic modeling approach for supplier selection. To help accomplish this objective the paper begins with a brief discussion on the issues facing organizations in strategic supplier selection. To help set the foundation of this model we summarize a number of sustainability factors that have been considered in the literature. These factors may then be integrated into a “Triple-Bottom-Line” model. Even though we do not present this model in all its detail it provides some starting point for organizations on factors they can consider in evaluating suppliers. The next section of the paper demonstrates an illustrative case application of the proposed model. The results provide interesting managerial insights, implications, and possible avenues for future research and development of the model. These issues will be summarized and presented in the final section. Our contributions from this study include: (1) modeling the decision problem within the context of a sustainable supply chain management decision; (2) incorporating additional layers and levels of variable and decision maker weighting schemes; and (3) providing additional rough set decision environments that help evaluate the sensitivity of the technique, allowing users and researchers to identify advantages and limitations in the approach.

In this paper we have introduced a multi-stage, multi-method approach to help evaluate the supplier selection decision with the recommendation of using sustainability factors. We focused on the integration of generic sustainability metrics and attributes based on the literature and provided examples of various triple-bottom-line attributes that could be included in the methodology. The number and type of attributes provides evidence of the complex nature of sustainability decisions and how techniques to manage these attributes and their application to supplier selection decisions set the stage for the methodology proposed in this paper. This methodology integrates rough set and grey system theory into an eight stage decision support process. Rough set theory allows for distillation of a larger set of suppliers into a smaller set of candidate preferred suppliers, and eventually the selection of a preferred supplier. Grey system theory is capable of integrating intangible and subjective decision maker importance and attributes valuations into the decision process. It also helps in the ranking and further identification of a preferred supplier. Rough set theory application to supplier selection and decision making contributes through use of historical decisions integrating previous organizational knowledge and learning into the latest decision process. As time progresses, organizations can further refine their decision making quality to either maintain some consistency and/or improve their decision process with further weighting and development of attributes that are salient for the organization's strategic direction. This approach helps in this process. We also showed that the final decision may be sensitive to the attributes that are used in the evaluation process. Practically, organizations that do not use the full complement of attributes to select suppliers or for outsourcing in a world where sustainability has gained significant importance by governments, communities, industry, customers, and markets, may have competitive disadvantage consequences.