INFORMATICA Informatica 1822-88440868-49520868-4952 Vilnius University INFOR497 10.15388/22-INFOR497 Research Article Taxonomy Method for Multiple Attribute Group Decision Making Under the Spherical Fuzzy Environment DiaoFengxia1

F. Diao is a graduate student at the School of Mathematics, Sichuan Normal University. Her research interests include multi-criteria group decision making, fuzzy sets, and spherical fuzzy sets.

 CaiQiang2

G. Wei has an MSc and a PhD degree in applied mathematics from SouthWest Petroleum University, business administration from school of Economics and Management at SouthWest Jiaotong University, China, respectively. From May 2010 to April 2012, he was a postdoctoral researcher with the School of Economics and Management, Tsinghua University, Beijing, China. He is a professor in the School of Business at Sichuan Normal University. He has published more than 100 papers in journals, books and conference proceedings including journals such as Omega, Decision Support Systems, Expert Systems with Applications, Applied Soft Computing, Knowledge and Information Systems, Computers & Industrial Engineering, Knowledge-Based Systems, International Journal of Intelligent Systems, International Journal of Uncertainty, Fuzziness and Knowledge-Based Systems, International Journal of Computational Intelligence Systems, International Journal of Machine Learning and Cybernetics, Fundamenta Informaticae, Informatica, Kybernetes, International Journal of Knowledge-Based and Intelligent Engineering Systems and Information: An International Interdisciplinary Journal. He has published 1 book. He has participated in several scientific committees and serves as a reviewer in a wide range of journals including Computers & Industrial Engineering, International Journal of Information Technology and Decision Making, Knowledge-Based Systems, Information Sciences, International Journal of Computational Intelligence Systems and European Journal of Operational Research. He is currently interested in aggregation operators, decision making and computing with words.

 WeiGuiwuweiguiwu1973@sicnu.edu.cn12∗

Q. Cai was born in 1968. He received the PhD in management science from University of Electronic Science and Technology of China, in 2009. He is currently a professor at the Busines School, Sichuan Normal University. He has contributed more than 40 journal articles to professional journals, such as Journal of Management Sciences in China, Systems Engineering-Theory & Practice, Chinese Journal of Management Science, Journal of Industrial Engineering and Engineering Management, Journal of Systems Engineering, and so on. His current research interests include energy finance, option game theory, computational finance, and technology innovation investment and management.

 School of Mathematical Sciences, Sichuan Normal University, Chengdu, 610101, PR China School of Business, Sichuan Normal University, Chengdu, 610101, PR China Corresponding author. 202226920223347137298202192022 © 2022 Vilnius University2022 Open access article under the CC BY license.

In recent years, the multi-attribute group decision making (MAGDM) problem has received extensive attention and research, and it plays an increasingly important role in our daily life. Fuzzy environment provides a more accurate decision-making environment for decision makers, so the research on MAGDM problem under fuzzy environment sets (SFSs) has become popular. Taxonomy method has become an effective method to solve the problem of MAGDM. It also plays an important role in solving the problem of MAGDM combined with other environments. In this paper, a new method for MAGDM is proposed by combining Taxonomy method with SFSs (SF-Taxonomy). In addition, we use entropy weight method to calculate the objective weight of attributes, so that more objective results can be produced when solving MAGDM problems.

 multi-attribute group decision-making (MAGDM) spherical fuzzy sets (SFSs) taxonomy entropy method Introduction

In order to improve the accuracy of decision-making, Zadeh (1965) put forward the concept of a fuzzy set, in which the relationship between hesitation degree, membership degree and non-membership degree is expounded. Many scholars have done related research on the fuzzy set and extended it further (Li and Wan, 2014a, 2014b; Lei et al., 2021a, 2021b, Wei et al., 2021). On the basis of predecessors, Atanassov (1986) proposed intuitionistic fuzzy sets (IFSs), so many scholars have studied the problem of MADM based on IFSs (Xian et al., 2017a, 2017b; Ye, 2017; Garg, 2018a, 2018b). For example, Liu et al. (2021) used IFSs to deal with uncertainty in data. Kaur and Garg (2018) presented an intuitionistic method for cubic intuitionistic fuzzy environment and carried out a comparative analysis. Liu et al. (2021) proposed an improved precision function to accurately compare some interval IFSs. Xu et al. (2012) used IFSs to deal with the problem of information uncertainty in air target threat assessment. Xue et al. (2021) studied the problem of data retrieval based on IFSs. Lei et al. (2020) defined the intuitionistic fuzzy Taxonomy method. Zhao et al. (2021a) improved TODIM method for IF-MAGDM based on cumulative prospect theory (CPT). Zhao et al. (2021b) extended CPT-TODIM method for interval-valued IF-MAGDM. In addition, scholars (Garg and Arora, 2021; Tao et al., 2021; Zhang et al., 2021; Mishra et al., 2020) et al. also conducted related studies on IFSs. Kutlu Gündoğdu and Kahraman (2019a) extended the IFSs to form spherical fuzzy sets (SFSs), in which the quantitative relations among membership, non-membership and hesitation are defined, and they satisfy 0 ⩽ μ ¯ Z s 2 ( a ) + ν ¯ Z s 2 ( a ) + π ¯ Z s 2 ( a ) ⩽ 1. SFSs have a wide range of applications, such as military, game theory, etc., and also arouse a wide range of interest among scholars. In order to make SFSs work better, Kutlu Gündoğdu and Kahraman (2019a) defined distance and geometric operation. Mathew et al. (2020) proposed a new framework combining AHP and TOPSIS with SFSs. A new spherical fuzzy geometric average formula is proposed to calculate the weight of the spherical fuzzy criterion. Aydogdu and Gul (2020) proposed a new spherical fuzzy set entropy measure, and combined SFSs with WASPAS to evaluate the product, proving the feasibility of the method. Fernandez-Martinez and Sanchez-Lozano (2021) extended SFSs to a wider range of contexts constituting a new field in the context of AI problem studies, thereby expanding the scope for membership levels defined in imprecise cases. In addition, a lot of scholars (Ullah et al., 2018; Kutlu Gündoğdu and Kahraman, 2019b; Zeng et al., 2019; Ashraf et al., 2019) have also carried out related research on it.

Taxonomy was proposed in 1763 and subsequently extended by a Polish mathematical group, and introduced as a means of classifying and determining levels of development (Jurkowska, 2014; Bienkowska, 2013). This method is very useful for classifying, categorizing, and comparing various methods to evaluate the advantages of the attributes of the study (Hellwing, 1968a,b). In recent years, some scholars have applied this method to decision analysis under some circumstances. For example, Xiao et al. (2020) combined the Taxonomy method with IFSs to solve the selection problem of green supply chain, and proposed an objective weighting method to improve the effectiveness of the algorithm. Wei et al. (2020) applied Taxonomy to select and rank low-carbon tourism destinations based on the Pythagorean fuzzy environment. He et al. (2019) combined Taxonomy with Pythagorean 2-Tuple linguistic classification method to select the provision of medical devices, and also adopted comparative analysis to prove the practicality of this method. These examples also prove that this method can be combined with other environments and provides a better decision method for solving MAGDM problems in other environments.

According to the existing literature on the study of SFSs, we have not found a method to use Taxonomy to solve the problem of MAGDM in the background of SFSs. Therefore, it is necessary to combine SFSs and Taxonomy to solve the MAGDM problem in this paper, which will provide a new method to solve the MAGDM problem in SFSs. This paper uses case analysis to carry on the concrete calculation, and also makes the relative comparison with the other methods which have been proved in this environment to confirm the practicability of this method. To this end, this paper has the following research ideas: (1) Use SFSs to express the decision maker’s (DM) overall evaluation of the method. (2) Combine Taxonomy method with SFSs, and present the specific calculation process. (3) Take car rental as an example to present the actual operation method of the algorithm. (4) Compare and verify the method in this paper with the existing method in this environment.

This paper is structured as follows: Firstly, SFSs and Taxonomy methods are briefly introduced and their applications are introduced. Secondly, in order to make readers better understand the method, we listed the formulas and calculation steps related to SFS and Taxonomy in this part. Later, we used the example to carry out specific operations. In order to verify the correctness of this method, we used the existing SF-VIKOR and SF-TOPSIS methods for verification. Finally, we compare and summarize the methods.

 Preliminaries Spherical Fuzzy Sets (Kutlu Gündoğdu and Kahraman, <xref ref-type="bibr" rid="j_infor497_ref_016">2019b</xref>)<italic>.</italic>

The definition of an SFSs, each a to Z s below represents our membership degree ( μ ¯ Z s ( a )), non-membership degree ( ν ¯ Z s ( a )) and hesitation number ( π ¯ Z s ( a )), The relationship between them satisfies the following formula Z s = { a ( μ ¯ Z s ( a ) , ν ¯ Z s ( a ) , π ¯ Z s ( a ) ) | a ∈ A } , where μ ¯ Z s : A → [ 0 , 1 ] , ν ¯ Z s : A → [ 0 , 1 ] , π Z s : A → [ 0 , 1 ]. In addition, they will also need to satisfy 0 ⩽ μ ¯ Z s 2 ( a ) + ν ¯ Z s 2 ( a ) + π ¯ Z s 2 ( a ) ⩽ 1, ∀ a ∈ A.

 (Kutlu Gündoğdu and Kahraman, <xref ref-type="bibr" rid="j_infor497_ref_016">2019b</xref>)<italic>.</italic>

Some basic operations about SFSs.

Add operation X s ⊕ Y s = { ( μ ¯ X s 2 + μ ¯ Y s 2 − μ ¯ X s 2 μ ¯ Y s 2 ) 1 2 , ν ¯ X s ν ¯ Y s , ( ( 1 − μ ¯ Y s 2 ) π ¯ X s 2 + ( 1 − μ ¯ X s 2 ) π ¯ Y s 2 − π ¯ X s 2 π ¯ Y s 2 ) 1 2 } .

The multiplication X s ⊗ Y s = { μ ¯ X s μ ¯ Y s , ( ν ¯ X s 2 + ν ¯ Y s 2 + ν ¯ X s 2 ν ¯ Y s 2 ) 1 2 , ( ( 1 − ν ¯ X s 2 ) π ¯ X s 2 + ( 1 − μ ¯ X s 2 ) π ¯ Y s 2 − π ¯ X s 2 π ¯ Y s 2 ) 1 2 } .

Multiplication by a scalar τ Z s = { ( 1 − ( 1 − μ ¯ Z s 2 ) τ ) 1 2 , ν ¯ X s τ , ( ( 1 − μ ¯ X s 2 ) τ − ( 1 − μ ¯ X s 2 − π ¯ X s 2 ) τ ) 1 2 } , τ > 0 . 0.\end{aligned}\]]]>

X s τ = { μ ¯ X s , ( 1 − ( 1 − ν ¯ X s 2 ) τ ) 1 2 , ( ( 1 − ν ¯ X s 2 ) τ − ( 1 − ν ¯ X s − π ¯ X s 2 ) τ ) 1 2 } , τ > 0 . 0.\end{aligned}\]]]>

For any set of fuzzy numbers X s = ( μ ¯ X s , ν ¯ X s , π ¯ X s ) and Y s = ( μ ¯ Y s , ν ¯ Y s , π ¯ Y s ), this is true for τ , τ 1 , τ 2 ⩾ 0. ( i ) X s ⊕ Y s = X s ⊕ Y s , ( ii ) X s ⊗ Y s = X s ⊗ Y s ( iii ) τ 1 X s ⊗ τ 2 X s = ( τ 1 + τ 2 ) X s , ( iv ) τ ( X s ⊕ Y s ) = τ X s ⊕ τ Y s , ( v ) ( X s ⊗ Y s ) τ = X s τ ⊗ Y s τ , ( vi ) X s τ 1 ⊗ X s τ 2 = X s τ 1 + τ 2 .

(Kutlu Gündoğdu and Kahraman, <xref ref-type="bibr" rid="j_infor497_ref_019">2020</xref>, <xref ref-type="bibr" rid="j_infor497_ref_017">2019c</xref>)<italic>.</italic>

Spherical Weighted Arithmetic Mean (SWAM) and Spherical Weighted Geometric Mean (SWGM). SWAM δ ( Z s 1 , Z s 2 , … ⋯ , Z s n ) = δ 1 Z s 1 + δ 2 Z s 2 + ⋯ + δ n Z s n = { [ 1 − ∏ i = 1 n ( 1 − μ ¯ Z s i 2 ) δ i ] 1 2 , ∏ i = 1 n ν ¯ Z s i δ i , [ ∏ i = 1 n ( 1 − μ ¯ Z s i 2 ) δ i − ∏ i = 1 n ( 1 − μ ¯ Z s i 2 − π ¯ Z s i 2 ) δ i ] 1 2 } , where δ i ∈ [ 0 , 1 ]; ∑ i = 1 n δ i = 1. SWAM δ ( Z s 1 , Z s 2 , … , Z s n ) = Z s 1 δ 1 + Z s 2 δ 2 + ⋯ + Z s n δ n = { ∏ i = 1 n μ ¯ Z s i δ i [ 1 − ∏ i = 1 n ( 1 − ν ¯ Z s i 2 ) δ i ] 1 2 , [ ∏ i = 1 n ( 1 − ν ¯ Z s i 2 ) δ i − ∏ i = 1 n ( 1 − ν ¯ Z s i 2 − π ¯ Z s i 2 ) δ i ] 1 2 } .

(Kutlu Gündoğdu and Kahraman, <xref ref-type="bibr" rid="j_infor497_ref_015">2019a</xref><italic>,</italic> <xref ref-type="bibr" rid="j_infor497_ref_018">2019d</xref>)<italic>.</italic>

The calculation formula of the score function and the accuracy function is given below Score ( X s ) = ( μ ¯ X s − π ¯ X s ) 2 − ( ν ¯ X s − π ¯ X s ) 2 .

The score function is used to compare the size of two fuzzy numbers. If the scoring functions are equal, then compare the calculations and compare the accuracy functions. Accuracy ( X s ) = ( μ ¯ X s ) 2 + ( ν ¯ X s ) 2 + ( π ¯ X s ) 2 .

Note that X s < Y s if and only if

Score ( X s ) < Score ( Y s ) or

Score ( X s ) = Score ( Y s ) and Accuracy ( X s ) < Accuracy ( Y s ).

(Szmidt and Kacprzyk, <xref ref-type="bibr" rid="j_infor497_ref_031">2000</xref>)<italic>.</italic>

Euclidean distance formula: d ( X s , Y s ) = 1 2 n ∑ i = 1 n ( ( μ X s − μ Y s ) 2 + ( ν X s − ν Y s ) 2 + ( π X s − π Y s ) 2 ) .

The Taxonomy Method

Taxonomy was proposed in 1763, subsequently extended by a Polish mathematical group, and introduced as a means of classifying and determining levels of development (Jurkowska, 2014; Bienkowska, 2013). The classical Taxonomy method is given as follows.

Step 1. Calculate the mean and standard deviation of attributes: a ¯ j = 1 m ∑ i = 1 m a i j ; j = 1 , 2 , … , n , S j ⌢ = 1 m ∑ i = 1 m ( a i j − a ¯ j ) 2 ; j = 1 , 2 , … , n . Step 2. Because in matrix decision making alternative solutions have different measurement scales in attributes, this stage is for balancing its different units, so the following formula is used to achieve this goal (Hellwing, 1968a, 1968b, 1968c). L i j = a i j − a ¯ j S j ˆ ; i = 1 , … , m , j = 1 , … , n . Step 3. Calculate the distance of each alternative relative to the other alternatives using the formula below (Hellwing, 1968a, 1968b, 1968c). P a b = ∑ j = 1 n ( l a j − l b j ) 2 , where a and b represent the alternatives being evaluated in order to facilitate the comparison of the two alternatives, and the following composite distance matrix can be obtained: P = p 11 ⋯ p 1 j ⋯ p 1 n ⋮ ⋱ ⋮ ⋱ ⋮ p i 1 ⋯ p i j ⋯ p i n ⋮ ⋱ ⋮ ⋱ ⋮ p m 1 ⋯ p m j ⋯ p m n m × n ; i = 1 , … , m , j = 1 , … , n . Step 4. Calculate the mean and standard deviation of the minimum distance in each row according to the calculation formula o ′ = 1 m ∑ i = 1 m o i ˆ , S o ⌢ = 1 m ∑ i = 1 m ( o i ˆ − o ′ ) 2 .

In this calculation, o i ˆ indicates the optimal distance of each row. Then the formula (23) is used to determine the range that the composite distance matrix should meet. o = o ′ ± 2 S 0 ⌢ .

If every row has a value that doesn’t fall within this range, it will not work, and the mean and standard deviation of each row will need to be calculated again.

Step 5. By the standardized matrix calculation development pattern L i o = ∑ j = 1 n ( L i j − L 0 j ) 2 ; i = 1 , … , m , where L 0 j represents the ideal value of the jth attribute, depending on whether the attribute is benefit type or negative type. L i j represents the standard value of the jth attribute in the ith choice.

Step 6. Calculated the height of development L O = L ¯ i o + 2 S L i o .

Then, calculate the final progression order using the following formula: F i = L i o L o ; i = 1 , … , m .

The Taxonomy Method with SFSs

In this section, we combine Taxonomy method with SFS (SF-Taxonomy) method to solve the problem of MAGDM. Let L = { L 1 , L 2 , … , L m } be a set of alternatives, P = { P 1 , P 2 , … , P n } becomes a set of properties. w = { w 1 , w 2 , … , w i } is the set of weights for each attribute, where ∑ i = 1 n w i = 1. For a MAGDM problem, there are k experts for evaluation, and an expert set L ( k ) is formed, δ i is the weight of the expert, where satisfies ∑ i = 1 n δ i = 1. The steps are given below.

Step 1. Building a decision matrix L ( k ) = [ L i j k ] m × n = l 11 k l 12 k ⋯ l 1 n k l 21 k l 22 k ⋯ l 2 n k ⋮ ⋮ ⋱ ⋮ l m 1 k l m 2 k ⋯ l m n k m × n , i = 1 , 2 , … , m , j = 1 , 2 , … , n . Step 2. Convert the cost attribute to the benefit attribute, for example, given a cost type fuzzy number L i j = ( μ i j , v i j , π i j ) , we can get the fuzzy number of its benefit L i j = ( v i j , μ i j , π i j ) . Step 3. The decision matrices are aggregated using the SWAM operator in conjunction with the expert weights.

Step 4. The entropy weight method is used to calculate the weight of attributes.

The scoring function of the standard matrix is calculated, and the matrix obtained is normalized by the following formula: L ¯ i j = score ( l i j ) ∑ i = 1 n score ( l i j ) ; j = 1 , … , n .

Calculate the degree of entropy E ˆ j = − 1 ln n ∑ i = 1 n l ¯ i j ; j = 1 , … , n , 0 ⩽ E ˆ j ⩽ 1 .

Calculate the rate of degree of entropy ( D i ), and then get the weights of attribute D j = 1 − E ⌢ j ; j = 1 , … , n , w j = D j ∑ j = 1 n D j .

Step 5. The spherical fuzzy composite distance matrix is calculated (SFCDM). SFCDM = ∑ j = 1 n w j d ( μ i j , v i j , π i j ) , ( μ k j , v k j , π k j ) . Step 6. Select the minimum value of each row of SFCDM matrix, and calculate their mean ( S F O ¯) and variance ( S S F O ). From this we can get their online and offline. SF O ¯ = 1 m ∑ i = 1 m SFO i , S SFO = 1 m ( SFO i − SF O ¯ ) 2 . Step 7. Obtain the spherical fuzzy positive ideal solution (SFPIS) of each alternative SFPIS = ( max i μ i j , min i v i j , min i π i j ) . Step 8. Calculate the development pattern (SFDP), from which you can derive the relevant matrix SFDP = ∑ j = 1 n w j ( d ( SFPIS , SFL i ) ) , i = 1 , … , m . Step 9. Calculate the average value and upper limit (SFHLD), from which you can get the final scheme value (SFDA). The minimum value is the optimal calculation scheme: SFHLD = SFD P ¯ + 2 S SFDP , SFDA = SFDP SFHLD .

Case Analysis

A company needs to rent a car for a major event, and there are four types of car rental companies that can offer this service. L = { L 1 , L 2 , L 3 , L 4 } forms a collection of alternative firms. We measured the vehicles provided by these companies using four attributes: cost ( U 1 ), endurance time ( U 2 ), company distance ( U 3 ), and service ( U 4 ), among which U 1 and U 3 are cost-type attributes, while the rest are benefit attributes, the attribute weight is unknown. There are three experts who form Expert Set E = { E 1 , E 2 , E 3 } to score them, among which the expert weights are 0.41, 0.32, 0.27, respectively. Based on their assessment, three decisions were made in L ( k ) , proof of the decision was made by the k decision maker.

Step 1. A fuzzy evaluation matrix is given L p = [ L i j p ] m × n = ( l μ i j p , l ν i j p , l π i j p ) , i = 1 , 2 , … , m , j = 1 , 2 , … , n represents the evaluation of the pth decision maker for the M j criterion of plan W i in SFSs, as below Tables 1–3.

Decision matrix by DM1.

U 1 U 2 U 3 U 4
L 1 ( 0.25 , 0.31 , 0.12 ) ( 0.27 , 0.39 , 0.25 ) ( 0.34 , 0.23 , 0.52 ) ( 0.31 , 0.24 , 0.12 )
L 2 ( 0.11 , 0.25 , 0.31 ) ( 0.11 , 0.35.0.31 ) ( 0.32 , 0.35 , 0.53 ) ( 0.41 , 0.33 , 0.65 )
L 3 ( 0.53 , 0.32 , 0.25 ) ( 0.35 , 0.53 , 0.47 ) ( 0.220.38 , 0.35 ) ( 0.33 , 0.12 , 0.42 )
L 4 ( 0.01 , 0.23 , 0.23 ) ( 0.36 , 0.47 , 0.22 ) ( 0.32 , 0.53 , 0.32 ) ( 0.53 , 0.41 , 0.23 )

Decision matrix by DM2.

U 1 U 2 U 3 U 4
L 1 ( 0.43 , 0.22 , 0.22 ) ( 0.27 , 0.33 , 0.31 ) ( 0.42 , 0.33 , 0.25 ) ( 0.45 , 0.38 , 0.37 )
L 2 ( 0.53 , 0.32 , 0.39 ) ( 0.45 , 0.23.0.13 ) ( 0.42 , 0.38 , 0.36 ) ( 0.59 , 0.15 , 0.32 )
L 3 ( 0.43 , 0.52 , 0.41 ) ( 0.58 , 0.27 , 0.42 ) ( 0.55 , 0.39 , 0.43 ) ( 0.47 , 0.48 , 0.53 )
L 4 ( 0.28 , 0.05 , 0.43 ) ( 0.43 , 0.32 , 0.42 ) ( 0.02 , 0.42 , 0.54 ) ( 0.35 , 0.45 , 0.23 )

Step 2. To transform the cost-type index into the benefit-type index, as shown in Tables 4–6.

Decision matrix by DM3.

U 1 U 2 U 3 U 4
L 1 ( 0.39 , 0.43 , 0.33 ) ( 0.45 , 0.34 , 0.22 ) ( 0.46 , 0.31 , 0.51 ) ( 0.46 , 0.32 , 0.19 )
L 2 ( 0.35 , 0.16 , 0.27 ) ( 0.68 , 0.42.0.31 ) ( 0.33 , 0.58 , 0.31 ) ( 0.35 , 0.35 , 0.22 )
L 3 ( 0.13 , 0.27 , 0.35 ) ( 0.53 , 0.33 , 0.45 ) ( 0.53 , 0.45 , 0.25 ) ( 0.42 , 0.34 , 0.42 )
L 4 ( 0.35 , 0.54 , 0.28 ) ( 0.48 , 0.44 , 0.52 ) ( 0.32 , 0.31 , 0.32 ) ( 0.47 , 0.33 , 0.41 )

Decision matrix by DM1.

U 1 U 2 U 3 U 4
L 1 ( 0.31 , 0.25 , 0.12 ) ( 0.27 , 0.39 , 0.25 ) ( 0.23 , 0.34 , 0.52 ) ( 0.31 , 0.24 , 0.12 )
L 2 ( 0.25 , 0.11 , 0.31 ) ( 0.11 , 0.35.0.31 ) ( 0.35 , 0.32 , 0.53 ) ( 0.41 , 0.33 , 0.65 )
L 3 ( 0.32 , 0.53 , 0.25 ) ( 0.35 , 0.53 , 0.47 ) ( 0.38 , 0.22 , 0.35 ) ( 0.33 , 0.12 , 0.42 )
L 4 ( 0.23 , 0.01 , 0.23 ) ( 0.36 , 0.47 , 0.22 ) ( 0.53 , 0.32 , 0.32 ) ( 0.53 , 0.41 , 0.23 )

Decision matrix by DM2.

U 1 U 2 U 3 U 4
L 1 ( 0.22 , 0.43 , 0.22 ) ( 0.27 , 0.33 , 0.31 ) ( 0.33 , 0.42 , 0.25 ) ( 0.45 , 0.38 , 0.37 )
L 2 ( 0.32 , 0.53 , 0.39 ) ( 0.45 , 0.23.0.13 ) ( 0.38 , 0.42 , 0.36 ) ( 0.59 , 0.15 , 0.32 )
L 3 ( 0.52 , 0.43 , 0.41 ) ( 0.58 , 0.27 , 0.42 ) ( 0.39 , 0.55 , 0.43 ) ( 0.47 , 0.48 , 0.53 )
L 4 ( 0.05 , 0.28 , 0.43 ) ( 0.43 , 0.32 , 0.42 ) ( 0.42 , 0.02 , 0.54 ) ( 0.35 , 0.45 , 0.23 )

Step 3. The above decision matrix is aggregated using the SWAM operator to obtain Table 7.

Decision matrix by DM3.

U 1 U 2 U 3 U 4
L 1 ( 0.43 , 0.39 , 0.33 ) ( 0.45 , 0.34 , 0.22 ) ( 0.31 , 0.46 , 0.51 ) ( 0.46 , 0.32 , 0.19 )
L 2 ( 0.16 , 0.35 , 0.27 ) ( 0.68 , 0.42.0.31 ) ( 0.58 , 0.33 , 0.31 ) ( 0.35 , 0.35 , 0.22 )
L 3 ( 0.27 , 0.13 , 0.35 ) ( 0.53 , 0.33 , 0.45 ) ( 0.45 , 0.53 , 0.25 ) ( 0.42 , 0.34 , 0.42 )
L 4 ( 0.54 , 0.35 , 0.28 ) ( 0.48 , 0.44 , 0.52 ) ( 0.31 , 0.32 , 0.32 ) ( 0.47 , 0.33 , 0.41 )

Step 4. Equations (28)–(31) were used to calculate the objective weight ϖ 1 = 0.3798 , ϖ 2 = 0.5413 , ϖ 3 = 0.0243 , ϖ 4 = 0.0546. Step 5. SFCDM was calculated by equations (32), as shown in Table 8.

The overall decision matrix.

U 1 U 2 U 3 U 4
L 1 ( 0.33 , 0.34 , 0.23 ) ( 0.33 , 0.36 , 0.26 ) ( 029 , 0.39 , 0.45 ) ( 0.40 , 0.39 , 0.25 )
L 2 ( 0.26 , 0.25 , 0.33 ) ( 0.47 , 0.32.0.28 ) ( 0.44 , 0.35 , 0.42 ) ( 0.47 , 0.44 , 0.49 )
L 3 ( 0.39 , 0.34 , 0.35 ) ( 0.49 , 0.38 , 0.45 ) ( 0.40 , 0.37 , 0.36 ) ( 0.41 , 0.39 , 0.46 )
L 4 ( 0.33 , 0.08 , 0.32 ) ( 0.42 , 0.41 , 0.40 ) ( 0.45 , 0.13 , 0.41 ) ( 0.47 , 0.45 , 0.29 )

Step 6. Find the minimum value of each row of SFCDM matrix ( SFO i ), calculate its mean value ( SF O ¯) and its variance ( S SFO ). SFO 1 = 0.1058 , SFO 2 = 0.1058 , SFO 3 = 0.1181 , SFO 4 = 0.1190 , SF O ¯ = 0.1122 , S SFO = 0.0064. Step 7. From SFDP i and S SFO , it can be concluded that its upper and lower lines are SFO = SF O ¯ ± S SFO = 0.1122 ± 0.0064. Step 8. Obtain the optimal distance under fuzzy environment, as shown in Table 9.

The SFCDM.

L 1 L 2 L 3 L 4
L 1 – 0.1058 0.1396 0.1487
L 2 0.10583 – 0.1181 0.1234
L 3 0.1396 0.1181 – 0.1190
L 4 0.1487 0.1234 0.1190 –

Step 9. Compute the development pattern ( SFDP i ). SFDP 1 = 0.1418 , SFDP 2 = 0.088 , SFDP 3 = 0.1639 , SFDP 4 = 0.1004. Step 10. The mean value and variance of SFDP can be calculated. SFDP O ¯ = 0.1234 , S SFDP = 0.0307.

The SFPIS of each alternative.

U 1 U 2 U 3 U 4
( 0.39 , 0.08 , 0.23 ) ( 0.49 , 0.32 , 0.26 ) ( 0.45 , 0.13 , 0.36 ) ( 0.47 , 0.39.0.25 )

Similarly, the upper limit of SFDP can also be obtained by calculation. SFHLD = 0.1849. Step 11. The SFDA was calculated in Table 10.

The SFDA.

L 1 L 2 L 3 L 4
0.7669 0.4757 0.8867 0.5433

From the final value of SFDA obtained above, we can get the final scheme ordering as L 2 > L 4 > L 1 > L 3 {L_{4}}>{L_{1}}>{L_{3}}$]]>. From sorting, we can get L 2 as the optimal scheme we got, so we finally choose L 2 as the optimal provider in this activity.

 Comparative Analysis

In order to verify the correctness of the SF-Taxonomy method, we adopted the examples and original data previously given in the paper, and adopted the SF-TOPSIS (Kutlu Gündoğdu and Kahraman, 2021) and SF-VIKOR (Sharaf, 2021) methods that have been confirmed by scholars for verification. The results obtained by them are compared with those obtained by the method presented in this paper.

Compared with SF-TOPSIS Method

Step 1. The overall weight matrix is calculated and the SWAM operator is used for aggregation (see Table 11).

Shep 2. Calculate the score function of the overall weight matrix (see Table 12).

The overall weight matrix.

U 1 U 2 U 3 U 4
L 1 ( 0.21 , 0.66 , 0.13 ) ( 0.19 , 0.70 , 0.16 ) ( 0.24 , 0.64 , 0.30 ) ( 0.24 , 0.13 , 0.15 )
L 2 ( 0.21 , 0.52 , 0.21 ) ( 0.26 , 0.68.0.18 ) ( 0.21 , 0.73 , 0.29 ) ( 0.41 , 0.33 , 0.65 )
L 3 ( 0.27 , 0.63 , 0.21 ) ( 0.29 , 0.72 , 0.30 ) ( 0.26 , 0.73 , 0.24 ) ( 0.33 , 0.12 , 0.42 )
L 4 ( 0.13 , 0.52 , 0.19 ) ( 0.25 , 0.74 , 0.25 ) ( 0.16 , 0.76 , 0.25 ) ( 0.53 , 0.41 , 0.23 )

Step 3. The optimal distance (SFPIS) and the worst distance (SFNIS) are calculated according to the score function (see Table 13).

The score function of the overall weight matrix.

U 1 U 2 U 3 U 4
L 1 −0.233 −0.299 −0.136 0.132
L 2 −0.071 −0.159 −0.264 0.147
L 3 −0.083 −0.145 −0.213 0.101
L 4 −0.149 −0.240 −0.360 0.204

Step 4. Calculate the distance between the overall weight matrix and the SFPIS and the SFNIS (see Table 14).

The SFPIS and SFNIS.

U 1 U 2 U 3 U 4
SFNIS ( 0.37 , 0.65 , 0.23 ) ( 0.33 , 0.81 , 0.28 ) ( 0.46 , 0.71 , 0.20 ) ( 0.42 , 0.36 , 0.27 )
SFPIS ( 0.54 , 0.56 , 0.15 ) ( 0.55 , 0.63 , 0.30 ) ( 0.57 , 0.56 , 0.23 ) ( 0.55 , 0.48 , 0.26 )

Step 5. Calculate the closeness ratio of each alternative (SFCR) (see Table 15).

The distance between the overall weight matrix and the SFPIS and SFNIS.

D E ( L i j , X j − ) D E ( L i j , X j ∗ )
L 1 0.033 0.078
L 2 0.078 0.081
L 3 0.068 0.074
L 4 0.074 0.080

The closeness ratio of each alternative (SFCR).

Closeness ratio
L 1 0.2947
L 2 0.4893
L 3 0.4789
L 4 0.4807

According to the above calculation results of SF-TOPSIS method with the same data, we can get the final decision ranking of the scheme is L 2 > L 4 > L 3 > L 1 {L_{4}}>{L_{3}}>{L_{1}}$]]>. From the ranking of the results, it is not difficult to see that L 2 is the optimal decision of the scheme, so we will choose L 2 as the best choice for the company’s activities in the end.

 Comparison with SF-VIKOR Method

As above, we will also directly show the calculation results of SF-VIKOR method here.

Step 1.The decision matrix is aggregated using the SWAM operator.

Step 2. The SFPIS and SFNIS are obtained from the aggregation matrix (see Table 16).

Step 3. The weight distance R ¯ i j is calculated by combining the attribute weight (see Table 17).

The SFPIS and SFNIS.

U 1 U 2 U 3 U 4
SFNIS (0.24,0.36,0.34) (0.33,0.41,0.45) (0.27,0.43,0.45) (0.40,0.45,0.49)
SFPIS (0.43,0.18,0.23) (0.39,0.32,0.26) (0.45,0.28,0.36) (0.47,0.39,0.25)

Step 4. The separation measures R ¯ and Q ¯ i can be obtained (see Table 18).

The weight distance R ¯ i j .

U 1 U 2 U 3 U 4
R ˜ 1 j 0.1977 0.3382 0.0100 0.0141
R ˜ 2 j 0.1877 0.0558 0.0168 0.0523
R ˜ 3 j 0.2805 0.4049 0.0117 0.0483
R ˜ 4 j 0.2836 0.3740 0.0229 0.0160

Step 5. Sort R ¯ and S ¯, then determine S ¯ + , S ¯ − and R ¯ + , R ¯ − (see Table 19).

The separation measures R ¯ and Q ¯ i .

P 1 P 2 P 3 P 4
R ¯ 0.3382 0.1877 0.4049 0.3740
S ¯ 0.5599 0.3127 0.7455 0.6966

Step 6. Finally, Q ¯ i can be calculated to obtain scheme ordering. Take ν = 0 (Opricovic, 1998) in the following calculation (see Table 20).

The S ¯ + , S ¯ − and R ¯ + , R ¯ − .

R ¯ + 0.1877 R ¯ − 0.4049
S ¯ + 0.3127 S ¯ − 0.7455

The Q ¯ i .

Q ¯ 1 Q ¯ 2 Q ¯ 3 Q ¯ 4
0.6320 0.0000 1.0000 0.8723

According to Q ¯ i , it can be concluded that its ranking is Q ¯ 2 < Q ¯ 3 < Q ¯ 1 < Q ¯ 4 , so the ranking of the scheme is L 2 > L 3 > L 1 > L 4 {L_{3}}>{L_{1}}>{L_{4}}$]]>. Therefore, it can be seen that Z 2 is the optimal scheme.

 Comparative Analysis

In order to more clearly and intuitively see the results of these two methods and the SF-Taxonomy method, the results are shown in Table 21.

The comparative analysis result.

Methods Consequences
SF-TAXONOMY L 2 > L 4 > L 1 > L 3 {L_{4}}>{L_{1}}>{L_{3}}$]]>
SF-TOPSIS L 2 > L 4 > L 3 > L 1 {L_{4}}>{L_{3}}>{L_{1}}$]]>
SF-VIKOR L 2 > L 3 > L 1 > L 4 {L_{3}}>{L_{1}}>{L_{4}}$]]>

In order to improve the accuracy of comparison, we used the same case above to conduct a comparative study on the SF-TOPSIS method and the SF-VIKOR method, and found that the SF-Taxonomy method formed by applying the Taxonomy method in the SFS environment in this paper was objective and effective. The optimal solution is consistent when the optimal decision is made. There was little difference in the rankings for the rest. In the research of SF-Taxonomy method, entropy weight method is introduced to calculate the objective weight because the attribute weight is unknown, so as to make the result more accurate and objective.

 Conclusion

Through the study of SFSs by scholars and the application of Taxonomy method in other backgrounds, this paper combines Taxonomy method with SFSs to form a new method to solve the multi-attribute decision problem in SFSs environment. In this paper, the concrete steps of SF-Taxonomy method are given. In order to make readers understand the method more clearly, the paper also gives the relevant calculation example analysis. In order to verify the correctness of such methods, the SF-TOPSIS method and the SF-VIKOR method, which have been confirmed by scholars, were compared in the following part of the paper, and relevant comparative analysis was made. The optimal scheme obtained by them in comparison is consistent, which confirms the correctness of this method. In the future, this approach could also have important applications in other contexts.

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