Abstract
The purpose of this study is to develop an extension of CODAS method using picture fuzzy sets. In this respect, a new methodology is introduced to figure out how picture fuzzy numbers can be applied to CODAS method. COmbinative Distance-based Assessment (CODAS) is a new MCDM method proposed by Ghorabaee et al. Picture fuzzy sets (PFSs) are a new extension of ordinary fuzzy sets for representing human’s judgments having possibility more than two answers such as yes, no, refusal and neutral. Compared with other studies, the proposed method integrates multi-criteria decision analysis with picture fuzzy uncertainty based on Euclidean and Taxicab distances and negative ideal solution. ERP system selection problem is handled as the application area of the developed method, picture fuzzy CODAS. Results indicate that the new proposed method finds meaningful rankings through picture fuzzy sets. Comparative analyzes show that the presented method gives successful and robust results for the solutions of MCDM problems under fuzziness.
Introduction
Fuzzy sets theory began with Zadeh’s presentation in the middle of 1960 s [1] with the purpose of explaining the uncertainty of entities by assigning membership degrees ranging from 0 to 1. It emerged as a new concept presenting the vagueness in real life problems for all researchers. However, fuzzy sets theory had some diffuculties to express all uncertainty in the real life problem because of the non-membership degree [2]. Therefore, after introducing fuzzy sets theory, many extensions of fuzzy sets have been improved by several researchers.
First extension of fuzzy sets was presented by Atanassov [3] with the idea of intuitionistic fuzzy sets (IFSs). It was introduced as a generalized version of fuzzy set by using membership and non-membership degrees. Atanassov and Gargov [4] and Atanassov [5] presented interval-valued intuitionistic fuzzy sets (IVIFS) that consist of a membership function, a non-membership function, and a hesitancy function. Yager [6] developed Pythagorean fuzzy sets (PyFS) and Wang and Li [7] integrated power Bonferroni mean operator to Pythagorean fuzzy numbers. Lately, Cuong and Kreinovich [8] suggested picture fuzzy sets (PFSs) and explained the principal processings and specifications of PFSs. In real applications, it has been observed that some cases cannot be represented in IFS and Pythagorean fuzzy set (PyFS). For example, considering a voting system, human views contain many such responses: yes, no, abstain and refusal [9]. The picture fuzzy set is constituted with three functions to clarify the degree of membership, the degree of neutral membership and the degree of non-membership. As the only limitation, it is indicated that the sum of three degrees should not pass 1 at all [10]. Cuong [11] introduced the concept of picture fuzzy sets (PFSs) that was the answer for the human’s ideas consisting more than two answers like, yes, no, refusal and neutral. Classical voting system is an illuminative example of this idea because the voters can be grouped into four categories such as vote for, vote neutral, vote against and vote refusal [12].
Many researchers have contributed to the implementation of PFS with the models they have developed. Singh [13] proposed the geometrical interpretation of picture fuzzy sets and correlation coefficients for picture fuzzy sets. Furthermore, Son [14] proposed a novel distributed picture fuzzy clustering method on PFSs. The model between picture fuzzy clustering and intuitionistic fuzzy recommender systems for medical diagnosis is prepared by Thong [15]. Cuong and Hai [16] made a definition as first for fuzzy logic operators and presented important operations for fuzzy derivation forms in the Picture fuzzy logic. Moreover, Cuong et al. [17] studied the representative of picture fuzzy t-norm and t-conorm. Phong et al. [18] presented specific configuration of picture fuzzy relations.
Thong and Son [19] presented Automatic Image Fuzzy Clustering for picture fuzzy sets (AFC-PFS) to accomplish the appropriate number of groups for fuzzy clustering of PFS. Wei [20] presented the multi attribute decision making (MADM) method based on the picture fuzzy cross entropy model proposed in the article. Garg [21] proposed a model on picture fuzzy sets and used it to multiple criteria decision making (MCDM) problems. Son [22] presented the generalized picture distance measures and picture association measures. Moreover, Son and Thong [23] developed some combined prediction models by using picture fuzzy clustering for weather update from satellite image series. Wei [24] presented the TODIM approach for picture fuzzy multiple attribute decision making problems. In 2018, Jana et al. [25] proposed some aggregation operators that is named as Dombi operators for PFSs conditions and applied these actions to MADM process. Wei and Gao [26] proposed the common dice likeness surveys for PFSs. Wei [27] presented picture fuzzy Hamacher collection operators with traditional Hamacher processes at MADM. Wei et al. [28] presented the projection models by using picture fuzzy information for multi attribute decision making problems. Wei et al. [29] defined picture 2-tuple linguistic operators in MADM. Wei [30] also defined some picture uncertain linguistic Bonferroni mean operators for MADM.
Ashraf et al. [31] proposed a model of cubic picture fuzzy sets that was the extension form of picture fuzzy sets. In 2019, Ashraf et al. [32] improved a new approach on geometric aggregation operators and TOPSIS method to understand the ambiguity in decision making problems for picture fuzzy sets. Zeng et al. [33] explored the exponential Jensen Picture fuzzy divergence measure and examined its implementations in multi-criteria decision making (MCDM) problems. Moreover, applications to PFSs can be accomplish to many real world cases like decision-making problems [20, 34], shareholder voting [35], geographic data clustering [36] and weather nowcasting [23].
The motivation of our paper is to integrate the superiorities of CODAS method and picture fuzzy sets. CODAS method’s superiority is that it is based on not only Euclidean distance but also Taxicab distance. Decisions should not be based on only direct distances between ideal solutions and alternatives but also indirect distances. On the other hand, picture fuzzy sets present a possibility for decision makers to express their hesitancy and refusal degrees at the same time. Therefore, we develop a new methodology to overcome MCDM problems, which is based upon CODAS method under picture fuzzy environment. CODAS (Combinative Distance-based ASsessment) method was first presented by Ghorabaee et al. [37]. By considering CODAS method many advantages can be realized that have not considered in other multi criteria decision making (MCDM) methods. The advantage of the CODAS method over other distance-based decision-making methods is that it is based on two types of distances. Using two types of distances in the assessment process leads to improve the accuracy of the ranking results [38].
To show the validity of the proposed picture fuzzy CODAS (PF-CODAS) method, an application to enterprise resource planning (ERP) system problem (adopted from [39]) is presented.
Due to the difficulties and constraints on business organizations, ERP system selection is critical and time consuming process. Nevertheless, the importance of selecting an appropriate ERP system should not be underlined, given the significant financial investments and potential risks and benefits [40]. Selection of the suitable ERP system is important for the successful implementation of ERP projects. Therefore, in this study, a method for removing the ambiguity in linguistic evaluations has been developed for the ERP system selection problem.
The remainder of the paper is organized as follows. In Section 2 literature review on CODAS method and current literature on ERP selection problems are given. In Section 3 the basic concepts of PFS and the steps of the crisp CODAS method are proposed. In Sections 4 and 5, the steps of the proposed PF-CODAS method and an explanatory numerical example are presented, respectively. Finally, a comparative analysis is presented in Section 6 and the study is concluded in Section 7.
Literature review
Because of its approach to MCDM problems, CODAS method has been often employed in the solution of numerous problems in the literature. CODAS method has been extended by almost all of the fuzzy set types except picture fuzzy sets. The integration of picture fuzzy sets and CODAS will fill a gap that has not yet been addressed in the literature. Within the scope of literature research, “CODAS” and “ERP Selection” keywords are searched on the web of science database and a brief analysis is done about the results. These articles are summarized in this section.
Literature review on CODAS method
The CODAS method was firstly presented by Ghorabaee et al. [37] to solve complex MCDM problems. In this study, the results of the CODAS method were compared with some of the actual MCDM methods and as a result, it has been revealed that the CODAS method is an effective application to deal with MCDM problems [41]. Ghorabaee et al. [38] also presented a combined model that contains the fuzzy logic and CODAS method for multi-criteria group decision-making problems to get the best suppliers. In order to develop CODAS method, linguistic terms and corresponding trapezoidal fuzzy numbers (TrFNs) were included.
Panchal et al. [42] proposed an integrated MCDM method for examining the maintenance decision problem in a process industry, and the basis of this method is the fuzzy analytical hierarchy process (FAHP) and a current fuzzy CODAS method. Badi et al. used CODAS method for location selection of desalination facilities [43] and for supplier selection in the steelmaking company [44]. Boltürk [45] presented the pythagorean fuzzy extension of CODAS method, namely Pythagorean fuzzy CODAS, for the problem of selection the best supplier. Later, Boltürk and Kahraman [46] developed an intuitionistic fuzzy CODAS method, called Interval-Valued Intuitionistic Fuzzy CODAS, to select wave energy facility location and the obtained results were compared with crisp CODAS method’s. As a result of the study, a different ranking was obtained by stating the reason for new ranking clearly. Mathew and Sahu [47] solved two material handling equipment (conveyor and automated guided vehicle) selection problem using various newly developed CODAS, EDAS, WASPAS and MOORA methods. The rankings resulted with these four approaches were compared with other popular approaches like TOPSIS and ELECTRE.
Peng and Garg [48] proposed weighted distance based approximation (WDBA), CODAS and a new method for constructing of distance measure and similarity measure to handle interval-valued fuzzy soft decision-making problems. Pamucar et al. [49] introduced Pairwise-CODAS model in which modification of the CODAS method was carried out using Linguistic Neutrosophic Numbers (LNN). Yeni and Ozcelik [50] presented interval-valued Atanassov intuitionistic fuzzy CODAS (IVAIF-CODAS) method for the solution of the MCGDM problem. Adalı and Tuş [51] presented a model including CRITIC to calculate the objective weights and TOPSIS, EDAS, CODAS methods to measure performances of hospital site alternatives.
Interval-valued neutrosophic CODAS method was developed by Karaşan et al. [52] for the selection problem among wind energy plant locations. Ijadi Maghsoodi et al. used hybrid decision-making approaches for a material selection problem [53] by applying Step-Wise Weight Assessment Ratio Analysis (SWARA) method and CODAS and for a site selection problem [54] by applying Best-Worst Method (BWM) method and CODAS. Interval-valued intuitionistic trapezoidal fuzzy sets (IVITrFS) and CODAS method are the basis of a new integrated model proposed by Seker [41]. In this study, a different ranking was obtained and superiority of the new method was explained.
Studies in the literature indicate that various fuzzy number extensions considered under uncertainty are integrated with the CODAS method. In this respect, picture fuzzy extension of CODAS method is emphasized in this study which has not been discussed in the literature yet.
Current literature on ERP selection problems
Market competition between companies in international markets has significantly changed the business environment by decreasing total costs, increasing return on investments, shortening product delivery times and providing sensitivity to customer demands. In this direction, enterprises should use effective corporate information systems in order to increase their competitive advantage. ERP is becoming more critical due to its capability to combine material, finance, and information flow and support organizational strategies [55, 56]. Gable and Stewart [57] defines ERP as one of the best application for accomplishing competitive advantage for enterprises. By this way, it can be concluded that ERP selection process is crucial for ensuring competitiveness and agility of the companies.
All ERP applications have different possibilities. Therefore, any of the ERP application will not provide best solutions to enterprises [40, 59]. It can be stated that examining flexibility of ERP systems will lead decision maker to choose the best ERP system between alternatives.
Many researches have been conducted about ERP selection in literature. Most of the studies have been leaded to explain the ERP selection process for larger enterprises [60–62]. In other way, some studies have focused on small medium enterprises (SMEs) [63–65]. Illa et al. [60] improved a new methodology for ERP selection which is called SHERPA. The mentioned methodology based on natural language definitions of the system domain, user needs and candidate ERP solutions. Badri et al. [66] proposed a 0–1 goal programming model to choose information system between alternatives according to multiple criteria including benefits, hardware, software and other costs, risk factors, preferences of decision makers and users, completion time, and training time constraints.
Lin and Ford [64] developed a road map for SMEs and classified the selection process in five steps. The steps are containing project initiation, business process reengineering, business requirements, creating a business case and the selection process. Yen and Sheu [67] presented competitive preferences as volume and flexibility. Defining ERP selection process as competitiveness, ERP packages should let simple information contribution, higher regional self goverment, easier log in to database and more software applications conformation.
Liao et al. [68] proposed a new model according to the 2-tuple linguistic information computing. Consistency and inconsistency indices have been defined taking into account the information acquired from internal interviews with ERP vendors. In addition, a linear programming model is created to select the most appropriate ERP system.
Vatansever and Uluköy [69] addressed the issue of determining the most suitable software for the manufacturing industry using fuzzy AHP and fuzzy MOORA methods respectively to determine the weight of criteria and to evaluate the alternatives.
A four-step multi-criteria decision making approach has been proposed in 2019 by Hinduja and Pandey [70]. Three MCDM methods, namely DEMATEL, IF-ANP and IF-AHP, were used at different stages of the said approach. Intuitionistic fuzzy sets were used to capture the uncertainties and hesitations in decision makers’ judgments.
Preliminaries
In this section, the preliminaries on picture fuzzy numbers and steps of the crisp CODAS methodology are presented.
Basic concepts of picture fuzzy sets
where μ A (x) (ε [0, 1]) is named as the “degree of positive membership of A”, η A (x) (ε [0, 1]) is named as the “degree of neutral membership of A” and v A (u) (ε [0, 1]) is named as the “degree of negative membership of A”, and μA (x), ηA (x), νA (x) satisfy the following condition: 0 ≤ μ (x) + η (x) + ν (x) ≤1, ∀x ∈ X. Then for x ∈ X, π A (x) = 1 - (μ (x) + η (x) + ν (x)) could be named as the degree of refusal membership of x in A [8].
For two PFNs A and B, according to the Definition 3, then
The CODAS method is a newly developed and one of the current MCDM method. In the method, the distance measurements taken as a basis for selecting the best alternative from the available options are Euclidean and Hamming. The primary idea of CODAS method can be stated as the best option should have the farthest distance from the negative ideal solution. When the Euclidean distances of two options have the same crisp number, Hamming distances are compared to choose the best one [37]. The steps of CODAS method are as follows [37, 43]:
The threshold parameter (τ) can be set by decision-maker and this parameter’s value is between 0.01 and 0.05. If the difference between Euclidean distances of two alternatives is less than τ, these two alternatives are also compared by the Taxicab distance.
The higher H i , the most appropriate alternative.
According to definitions of PFS and CODAS method, the steps of presented picture fuzzy CODAS method are listed below.
If the criteria is occurred in cost type, the formulation below is used for normalization of the criteria. There is no need to normalization for benefit criteria in picture fuzzy sets [9].
Picture fuzzy weighted normalized matrix values are calculated by using Equation (8) where wj gets values between 0 and 1.
Score functions and accuracy functions are used to identify negative ideal solutions for all criteria. To calculate score and accuracy functions, Equation (5) and Equation (6) are determined. The lowest scores are defined as negative ideal solutions.
In this step, Equation (7) is implemented for calculating Euclidean distances. For determining Taxicab distance, the normalized hamming distance formula is used illustrated in Cuong and Kreinovich [8] as below:
The threshold parameter (τ) can be adjusted by decision-maker and this parameter’s value must be between 0.01 and 0.05. If the difference between Euclidean distances of two alternatives examined is less than τ, these two alternatives will be also calculated with the Taxicab distance.
In this section, the proposed Picture Fuzzy CODAS (PF-CODAS) method is applied to an example of enterprise resource planning (ERP) system problem which is adopted from [39]. Wei adapted this problem from Liao et al. [68]. There are five possible ERP systems At (t = 1, 2, ... 5) and four unquantifiable evaluation criteria Ci (i = 1, 2, 3, 4). These criteria are function and technology (C1), strategic fitness (C2), vendor’s ability (C3), vendor’s reputation (C4).
All the criteria are benefit-type in this study and the weights were determined by the decision-makers as follows respectively (0.2, 0.1, 0.3, 0.4).
Weights of the criteria for selected problem are known as a scope of this study taken from Wei [39]. There are few studies determining weights of the criteria in the literature. Zhang et al. [72] developed a new approach for the problem of two-sided matching decision making (TSMDM). In this study [72], the primary weight vector is obtained directly from “fuzzy preference relation with self-confidence” based on logarithmic least squares method. This approach also provides algorithms to improve consistency. For another study [73], an approach was developed with multi-granular hesitant fuzzy linguistic term sets for the TSMDM problem. Zhang et al. [73] created optimization models to assign criteria weights by not ensuring clear criteria weight vectors.
In order to determine the most suitable ERP system, the steps of the proposed PF-CODAS approach is presented as follows:
Picture fuzzy decision matrix
Picture fuzzy decision matrix
Weighted normalized picture fuzzy decision matrix and distances
Relative assessment matrix
In order to check the validity of the proposed PF-CODAS method in this study, example application is adopted from Wei [39]. In this context, the results are compared with the existing methods of PF-TOPSIS [74] and picture fuzzy aggregation operators [39]. PF-TOPSIS method is selected due to the similarity to the proposed PF-CODAS. Due to the application of Wei’s example, the results obtained in this study are also compared with the results of picture fuzzy aggregation operators as picture fuzzy weighted average (PFWA) and picture fuzzy weighted geometric (PFWG). The same weights of criteria are considered by these methods. The comparative results are shown in Table 4.
Comparison of proposed method with the existing methods
Comparison of proposed method with the existing methods
The preference order obtained by the proposed method and PF-TOPSIS [74], PFWA, PFWG operators provided by Wei [39] are slightly different but the desired best alternative is same. In all four methods, A3 is the best alternative, and A4 is the worst. According to the Table 5, the results of each method show A3 as the best alternative and A4 as the worst.
Ranking similarity for four methods
The Spearman’s rank correlation coefficient values (rs) are calculated for the comparative analysis of the methods (Table 5). The values in parentheses represent the correspondence for the ranked alternatives between the PF-CODAS method and other three methods as calculated by [75]. For example, the value of 40% at the intersection of the first row (PF-CODAS) and the second column (PF-TOPSIS) was obtained due to the fact that two of the five alternatives (A3 and A4) were in the same order according to the order of the two methods given in Table 4.
Based on the values of Spearman correlation coefficient, the ranks provided by the PF-CODAS method seem very similar to the PFWA method and a 60% correspondence is observed between these two methods. Also, PF-CODAS and PF-TOPSIS (and PFWG) are similar according to observed 40% correspondence [75].
In this paper, picture fuzzy CODAS method is presented based on traditional CODAS method. First of all, picture fuzzy sets and its basic definitions are briefly shown including Euclidean distance, Taxicab distance, score functions and accuracy functions. After definitions, extension of picture fuzzy sets with traditional CODAS method is proposed by methodology of the study. By using picture fuzzy numbers, decision makers can report their agreement, disagreement and hesitancy degrees and add them into decision making process. Finally, a numerical example for ERP selection problem has been given to express the new model and make comparisons between other picture fuzzy methods. As a result of numerical example, we state that Picture fuzzy CODAS method give meaningful results and rankings under fuzziness.
In order to present the validity of the proposed method in this study, statistical analysis is also used in comparison with other methods. Statistical values also indicate that the method presented gives valid results. Considering the difficulty of making decisions under uncertainty, the new method developed in our study will provide effective results in decision-making processes. Compared with previous methods, one of the advantage of our proposed method is that it is based on the negative ideal distance measure with lower processing complexity.
However, the results of this study are limited with ERP selection problem. In future, PF-CODAS method can be applied to many other decision-making problems such as machine selection or vehicle selection problems by management.
