The proposed method for solving this decision-making problem includes the following parts:
Part 1: Problem Inputs; In this section, the expectations of stakeholders, expert judgments and the required database are collected.
Part 2: Elicitation of attributes and constraints of the problem; In this section, based on the expectations of stakeholders and the expert opinions, problem constraints and effective attributes in decision making are determined.
Part 3: Determination of the relative importance of attributes; In this section, the process of determining the relative importance of attributes by experts or stakeholders is simulated.
Part 4: Identifying decision alternatives and valuing the attributes for each alternative; In this section, according to the constraints of the problem, decision alternatives are elicited from the database. The utilization of KDD techniques to elicit models will be done to determine quantitative values for each of the attributes from the database collected in this section.
Part 5: Evaluating, ranking and storing alternatives; In this section, the final score of each alternative is calculated using the evaluation function and the alternatives are prioritized accordingly. Generated rankings are stored for later analysis.
Part 6: Statistical analysis and sensitivity assessment of outputs; In this section, statistical analysis and sensitivity assessment of iterative problem-solving outputs with relative importance simulated for attributes are discussed. Determining the frequency of positions occupied in ranking, standard deviation, the number of positions occupied by each alternative and other statistical characteristics will be examined in this section.
Part 7: Finally, with statistical analysis and sensitivity assessment of stored outputs, a robust-reliable decision will be made to select benchmark platforms. Figure 1 shows the steps required to achieve a robust-reliable decision.
Implementation Of Methodology:
In this section, the proposed methodology for the decision problem is implemented.
Process inputs:
The inputs of this procedure consist of three main parts; stakeholders expectations, experts judgments, and database.
As can be seen in Figure 1, stakeholder expectations and expert judgments contain certain and uncertain statements. Certain statements will determine the type of decision attributes and constraints. And uncertain statements will determine the relative importance of the attributes. To elicit quantitative models for attributes and determination of their values, a database of automobiles and platforms has been compiled from all over the world. This database includes information such as automobile segments, models, manufacturers, years of production, annual production number, price, type of platform and platform manufacturer.
Elicitation of constraints and decision attributes:
According to the problem statement and the seven expectations of the stakeholders, in this section, the constraints and attributes of the decision problem have been elicited.
The constraints for defining the decision space are as follows:
- The automotive family developed based on each of the platform alternatives must include at least one of the segments of B or C or SS.
- The first automobile manufactured based on each of the platform alternatives must be less than 25 years old.
As can be seen in the problem statement, the stakeholder expectations are qualitative in nature and the measurement criteria are not set for them. Using the expert judgments, four attributes that meet the expectations of stakeholders can be defined which are quantified based on models and values elicited from the database. The four decision attributes extracted based on stakeholder expectations and expert judgments are:
1-Segment adaptation: This attribute is vital in defining the degree of compatibility of the platform within the segments that are defined for the development of the automotive family. The valuing is done based on the degree of resemblance between developed segments based on each alternative of the platform in the database and stakeholder expected segments.
2-Price: The price attribute itself consists of two sub-attributes; the minimum price and the price range of the automobiles developed based on each platform alternative. It is worth noting that since the automobiles have been manufactured in different countries over various periods of time, all prices should be standardized based on an underlying currency. U.S. dollar with its value in 2019 has been chosen here.
3-Platform flexibility: This attribute contains two sub-attributes; the number of segments covered by each alternative platform and the number of models produced based on each platform alternatives. Basically, a greater number of segments as well as number of models indicates a more flexible platform.
4-Platform popularity: it is also known as an attribute describing the level of popularity and reliance on a platform. Here this attribute is divided into two sub-attributes; the number of manufacturers using the platform, and the annual production rate of the automobiles based on the platform.
Generation of the relative importance of attributes:
The relative importance of attributes and sub-attributes is a function of stakeholder expectations and expert judgments. Due to the uncertainty in the statements, different expert judgments and different levels of stakeholder expectations, the relative importance of the attributes will also be variable and include uncertainty. In this study, to achieve a robust-reliable decision for all expert judgments and levels of stakeholder expectations, the process of determining the relative importance of attributes by experts and stakeholders has been simulated. In the simulation with the aim of "realizing the values" and avoiding unexpected values, the following constraints are considered:
- The relative importance of the attributes should be quantified by integers 1 to 9
- The probability distribution function of the relative importance of the attributes is uniform.
- None of the sets of the relative importance of the attributes is similar to each other.
Given that there are four main attributes, and the relative importance value of each attribute can be determined with numbers 1 to 9 based on the Thomas L. Saaty method, the number of possible non-repetitive states will be equal to 6561 states. By removing sets of weights that are multiples of each other, 6223 unique sets of relative importance will remain. Finally, we make the simulated weights of importance dimensionless, so that the total weight of the values in each set is equal to one.
It should be noted that in this study, for the weight of the importance of sub-attributes, constant values are considered. The hierarchical structure of the decision-making problem has been shown in Figure 2.
In Fig. 2 (W1 to W4) are the weight of the importance of the attributes. (w2.1, w2.2, w3.1, w3.2, w4.1, w4.2) are the weight of the importance of the sub-attributes. (P1 to P34) indicates the number of platform alternatives.
Alternatives definition and valuing the attributes:
By having applied the constraints in the database, the decision space is shrunk to 34 alternatives for the benchmark automotive platforms selection. Overall, the design space includes the database with 546 automotive models in 11 automotive segments that are developed based on 34 platforms.
In the design and decision-making process for new products, using data related to successful previous products will be a smart approach to reducing the level of uncertainty and lack of knowledge. In this study, in the decision-making process, instead of determining the values of each of the attributes based on human judgment (which is always accompanied by some degree of uncertainty), the values of the attributes are elicited from the database using KDD techniques. This approach has led to the elimination of uncertainties caused by human judgment in determining the values of attributes. On the other hand, given that the database contains the information of successful products that have been produced and tested, the values obtained for the attributes will be quite reliable.
Due to the different ranges of values of each attribute, to have a correct evaluation, the values of each attribute must be normalized. Different methods have been proposed in different references to normalize the values of attributes [61][62-65]. In different references, depending on the type of data and the decision-making method used, the normalization method has been proposed [63][65]. Accordingly, in this study, the vector normalization method has been used for the attributes. Eq. 1 and 2 have been used for vector normalization.

Table 1 presents the alternative platforms and the normalized values of each attribute. In calculating the values of the second to fourth attributes, the weights of importance of the sub-attributes are considered as follows (w2.1 = 0.5, w2.2 = 0.5 w3.1 = 0.3, w3.2 = 0.7, w4.1 = 0.5, w4,2 = 0.5).
Table 1 Normalized values of each attribute for 34 alternative platforms
Platform popularity
|
Platform flexibility
|
Price
|
Segment adaptation
|
Platform name
|
Alternative number
|
0.095153528
|
0.202686229
|
0.182013536
|
0.164581341
|
BMW CLAR
|
P1
|
0.024685363
|
0.061128889
|
0.16790174
|
0.08429776
|
BMW Life-Drive
|
P2
|
0.117095262
|
0.1470715
|
0.18160435
|
0.180638057
|
BMW UKL
|
P3
|
0.136152202
|
0.158336384
|
0.169173644
|
0.216765668
|
Fiat Compact
|
P4
|
0.107448857
|
0.06940013
|
0.170576084
|
0.080283581
|
Fiat Mini
|
P5
|
0.17902298
|
0.21647163
|
0.17583018
|
0.240850742
|
Fiat-GM Small
|
P6
|
0.078165236
|
0.105478735
|
0.167598151
|
0.130460819
|
Ford Global B
|
P7
|
0.153019627
|
0.105478735
|
0.163470422
|
0.130460819
|
Ford Global C
|
P8
|
0.068347266
|
0.06664305
|
0.147776025
|
0.100354476
|
Ford C2
|
P9
|
0.241278618
|
0.174642301
|
0.178270918
|
0.16658843
|
GM Delta
|
P10
|
0.211685177
|
0.194178426
|
0.166632773
|
0.130460819
|
GM Epsilon
|
P11
|
0.13624777
|
0.169364704
|
0.170583221
|
0.210744399
|
GM Gamma
|
P12
|
0.107185422
|
0.06664305
|
0.140584326
|
0.066233954
|
GM Lambda
|
P13
|
0.204184686
|
0.08318553
|
0.1674529
|
0.066233954
|
GM Theta
|
P14
|
0.205921376
|
0.157863257
|
0.188941466
|
0.130460819
|
Hyundai-Kia J
|
P15
|
0.127523108
|
0.160856901
|
0.167382373
|
0.180638057
|
Hyundai-Kia Small
|
P16
|
0.146401613
|
0.185907185
|
0.165009828
|
0.150531714
|
Hyundai-Kia Y
|
P17
|
0.057020541
|
0.06388597
|
0.150492769
|
0.100354476
|
Mercedes-Benz MFA
|
P18
|
0.061432921
|
0.06664305
|
0.157383536
|
0.100354476
|
Mercedes-Benz W176
|
P19
|
0.237729341
|
0.196935506
|
0.173356415
|
0.182645146
|
Mitsubishi GS
|
P20
|
0.088853527
|
0.06664305
|
0.154548261
|
0.100354476
|
PSA CMP EMP1
|
P21
|
0.171037562
|
0.158099821
|
0.161623071
|
0.16658843
|
PSA EMP2
|
P22
|
0.140163691
|
0.15534274
|
0.171256795
|
0.180638057
|
PSA PF1
|
P23
|
0.145379202
|
0.196935506
|
0.168637612
|
0.200708952
|
PSA PF2
|
P24
|
0.308422349
|
0.299184034
|
0.178562202
|
0.244864921
|
Renault-Nissan B
|
P25
|
0.16117707
|
0.127535376
|
0.171880116
|
0.130460819
|
Renault-Nissan C
|
P26
|
0.13977093
|
0.20820039
|
0.165136531
|
0.232822384
|
Renault-Nissan CMF
|
P27
|
0.107789784
|
0.15534274
|
0.168483536
|
0.16658843
|
Toyota B
|
P28
|
0.210957747
|
0.230257031
|
0.171609233
|
0.232822384
|
Toyota MC
|
P29
|
0.216064009
|
0.236007754
|
0.163940179
|
0.25088619
|
Toyota TNGA
|
P30
|
0.210119856
|
0.218992147
|
0.173267714
|
0.214758578
|
VW A
|
P31
|
0.201984047
|
0.182913542
|
0.175347234
|
0.180638057
|
VW A0
|
P32
|
0.180643915
|
0.196935506
|
0.251429802
|
0.130460819
|
VW MLB
|
P33
|
0.350619573
|
0.307691837
|
0.174337794
|
0.266942906
|
VW MQB
|
P34
|
Evaluating, ranking and storing of the alternatives:
At this stage, by determining the values of each attribute for the alternatives, and simulating the process of determining the relative importance of the attributes, the evaluation process of each alternative can begin. This process will be iterated as many times as simulation of the relative importance of attributes (6223 times) and finally, the obtained rankings will be stored for further analysis and identification of the robust-reliable decisions.
It is important to choose the right decision-making method that has the most reliable solution with the least complexity. For this study, the SAW method was selected due to the fact that this is the most widely used and oldest multi-attribute decision-making method [a, b, w, q, e, nr4]. Considering the type of the decision problem, i.e., decision-making under uncertainty with a large number of decision alternatives, this method will be superior to others in terms of reducing computational complexity. In this method, the evaluation function of each alternative is calculated using Eq. 3.

Statistical analysis and sensitivity assessment of outputs:
By looking at the 6223 stored data of rankings, it is possible to identify the different positions occupied by each alternative and to begin the process of analysis and sensitivity assessment accordingly. Figure 3 shows the positions occupied by each alternative in 6223 repetitions of the decision-making problem.
As can be seen in Figure 3, by changing the importance of the attributes, the alternatives occupy different positions in the ranking. Considering the five required benchmark platforms and the reduction of calculations, only the alternatives that have been able to occupy positions 1 to 5 at least once have been considered for further analysis (P6, P10, P15, P20, P25, P29, P30, P31, P33, and P34). Table 2 shows the frequency of occupancy of each position in the rankings of alternatives.
Table 2 The position occupied by each alternative and the frequency of their occurrence

In order to make the most robust decision, the sensitivity of the positions occupied by the alternatives in the ranking should be analyzed. The positions that have the most abundance could not necessarily be a reliable criterion for making the most robust decision. The parameters of the distribution of occupied positions and the frequency of occupation of each position determine the sensitivity of the position of an alternative in the ranking to changes in the relative importance of the attributes. The concept of standard deviation is a suitable criterion for analyzing the sensitivity of the occupied position of each alternative to the uncertainties of the relative importance of the attributes. Table 3 presents the statistical parameters related to the position of each alternative in the ranking.
Table 3 Statistical status of the alternatives in the ranking
The standard deviation of occupied positions in the ranking
|
The number of occupied positions in the ranking
|
The mean value of occupied positions in the ranking
(Mean rank number)
|
The percent of maximum repetition in
the ranking
|
The most frequented occupied position in the ranking (Mode)
|
Alt.No.
|
1.5801
|
9 positions
|
6.4023
|
%34.7
|
Rank 5
|
P6
|
2.3584
|
13 positions
|
9.3054
|
%27.3
|
Rank 8
|
P10
|
1.4271
|
10 positions
|
7.0700
|
%34.4
|
Rank 7
|
P20
|
0.0645
|
2 positions
|
2.0042
|
%99.5
|
Rank 2
|
P25
|
0.5803
|
4 positions
|
4.2269
|
%83.7
|
Rank 4
|
P29
|
0.5955
|
7 positions
|
3.1862
|
%88.4
|
Rank 3
|
P30
|
0.7667
|
4 positions
|
5.8415
|
%48.8
|
Rank 6
|
P31
|
3.5196
|
21 positions
|
9.0633
|
%15
|
Rank 9
|
P33
|
0.0506
|
2 positions
|
1.0026
|
%99.7
|
Rank 1
|
P34
|
Box diagrams can be used to better represent the diversity and distribution of occupied positions in the ranking. Figure 4 shows this diagram for each of the alternatives listed in Table 3.
In Figure 4, the black dots represent the mean position numbers are occupied by each alternative. The red lines indicate the median value, the lower side of the blue boxes indicates the value of the first quadrant (Q1) and the upper side indicates the value of the third quadrant (Q3). Red plus signs indicate outliers. Horizontal black lines represent the minimum and maximum values, which are defined based on Eq. 4 and 5, respectively.

Identification of the robust-reliable decision:
The following two criteria can be introduced to determine the most robust-reliable decision:
1. Achieving the highest relative position (mean position number) in the ranking for the different relative importance of attributes (desirability criterion)
Since there will be a possibility of change in the positions occupied by the alternatives for different weights of importance of the attributes, and on the other hand, for two alternatives, the highest repetitions may occur for the same positions of rankings, taking into account the mean of position numbers occupied by each alternative is a more reliable criterion for comparing the desirability of alternatives considering.
2. The lowest standard deviation in the occupied positions in the ranking (robustness criterion)
The lower standard deviation for an alternative, shown the higher focus on a given positions in ranking, that means the more robust to changing the relative importance of the attributes. In Table 4, the first five alternatives are selected based on each of the two criteria.
Table 4 Prioritization of alternatives based on two criteria of desirability and robustness
Prioritization based on the desirability
|
|
Prioritization based on the robustness
|
Prioritized alternatives
|
Alt.No.
|
Mean position in the ranking
|
Prioritized alternatives
|
Alt.No.
|
The standard deviation of occupied positions
|
The first
(The most desirable)
|
P34
|
1.0026
|
The first
(The most robust)
|
P34
|
0.05064086
|
The second
|
P25
|
2.0042
|
The second
|
P25
|
0.06450266
|
The third
|
P30
|
3.1862
|
The third
|
P29
|
0.58030464
|
The fourth
|
P29
|
4.2269
|
The fourth
|
P30
|
0.59554597
|
The fifth
|
P31
|
5.8416
|
The fifth
|
P31
|
0.76667009
|
As can be seen in Table 4, the alternatives P34 and P25 in both criteria have a higher priority than the other alternatives. The P30 alternatives are in the third priority of desirability, while in terms of robustness, the alternative P29, which is in the fourth desirability priority, is better than the alternative P30, but this superiority is not enough to affect the final prioritization of the alternatives.
Finally, the most robust-reliable decisions to select benchmark platforms to develop an automotive family according to the defined attributes by take into account all possible scenarios for stakeholders’ expectations and expert judgments can be seen in Table 5.
Table 5 The most robust-reliable decision in choosing the benchmark platforms
Prioritized alternatives
|
Alt.No.
|
Platform name
|
The first
(The most robust-reliable decision)
|
P34
|
VW MQB
|
The second
|
P25
|
Renault-Nissan B
|
The third
|
P30
|
Toyota TNGA
|
The fourth
|
P29
|
Toyota MC
|
The fifth
|
P31
|
VW A
|