2.1. Multi Criteria Decision and Metrics
MCDA provides a systematic framework for evaluating a number of alternatives based on several criteria that may have varying levels of importance. One of the most widely used MCDA methods is the Analytic Hierarchy Process (AHP), which was introduced by Saaty [
1]. AHP breaks down a decision problem into a hierarchical structure consisting of objectives, criteria, subcriteria, and alternatives. Decision-makers’ preferences are represented by a pairwise comparison matrix
for
n elements being compared. The matrix satisfies the reciprocity property
and
. The relative priority weights of each element can then be derived using the eigenvalue method to form a normalized priority vector.
These priority vectors represent the relative level of importance of each element relative to elements at a higher hierarchical level. The reliability of AHP results is determined not only by the priority weight values but also by the consistency of the evaluations provided by the decision-maker. Consistency is necessary because fully independent pairwise comparisons can result in contradictory preference relationships. For example, if criterion A is rated as more important than criterion B, and criterion B is rated as more important than criterion C, the assessment of the relationship between A and C should still follow a consistent pattern. In AHP, the level of inconsistency is generally evaluated using CI and CR.
Saaty [
22] uses a threshold of
as a general criterion for assessing whether the level of inconsistency is still acceptable. However, the use of a single consistency indicator is not always sufficient to fully characterize inconsistency. Brunelli et al. [
23] shows that consistency indices can have different sensitivities to patterns of inconsistency in pairwise comparison matrices. In addition to CR, several alternative indices have been developed, including Koczkodaj’s Index [
24] and the Geometric Consistency Index (GCI) [
25]. Koczkodaj’s Index [Koczkodaj, 1993] is defined as the minimum distance of a triad to its nearest consistent counterpart, extended to matrices of order n > 3 via the maximum such distance over all triads containing a given element, making it a global rather than purely local measure. Koczkodaj and Szwarc [
26] further show axiomatically that centroid- and eigenvalue-based indicators such as CR and GCI can fail to detect arbitrarily large inconsistencies as matrix order grows, a limitation the distance-based indicator does not share. This motivates including it in ThinkDecision as a diagnostic complement, particularly when transparency and auditability are required.
Although AHP is effective for modeling hierarchical decision structures, the assumption of independence among elements does not always align with the characteristics of real-world problems. In many cases, one criterion may influence another, while alternatives may also provide feedback on the criteria used. To accommodate these relationships, Saaty [
2] developed ANP as an extension of AHP. Unlike AHP, which uses a unidirectional hierarchical structure, ANP represents decision problems as a network that allows for interdependencies and feedback between elements and between clusters. These influence relationships are represented through the supermatrix
W, which consists of blocks of local priority matrices. After the cluster weights are taken into account, the unweighted supermatrix is transformed into a weighted supermatrix. If the regularity condition is satisfied, repeated exponentiation of the weighted supermatrix will yield a limit supermatrix, which represents the global priorities of all elements in the network. After the cluster weights are applied, the global priorities are obtained through the convergence of the weighted supermatrix to the limit supermatrix.
ANP has higher computational requirements than AHP because its calculation process involves forming local priority blocks, weighting supermatrices, and iterating until convergence is reached. In AHP, extracting a priority vector from a single
pairwise comparison matrix generally has a complexity of up to
when using the conventional eigenvalue approach. In ANP, each iteration on an
supermatrix can also incur a computational cost of up to
if implemented using dense matrix multiplication. The total computational load further depends on the network size, the sparsity of the supermatrix, the number of iterations, and the convergence tolerance used. A literature review by Sipahi and Timor [
15] shows that AHP and ANP have been widely applied in various decision-making domains. However, in computational implementations, the iteration parameters, stopping criteria, and convergence tolerance must still be explicitly reported to ensure the traceability and reproducibility of the results. Thus, ANP-based decision support systems must not only produce a final ranking but also provide information regarding the formation and convergence of the supermatrix.
The complexity of multi-criteria decision making stems not only from the structure of the relationships among criteria, but also from the decision-maker’s limitations in providing precise evaluations. In practice, preferences among elements are often expressed using linguistic terms, such as “slightly more important” or “much more important.” The single numerical representation in classical AHP is not fully capable of capturing the ambiguity and interpretive variation inherent in such assessments. Therefore, Fuzzy AHP was developed to represent linguistic uncertainty through fuzzy numbers [
3,
4,
27].
One of the most commonly used representations is the Triangular Fuzzy Number (TFN), which is expressed as
where
. The parameters
l,
m, and
u represent the lower bound, the most likely value, and the upper bound, respectively. This structure allows an assessment to be expressed as a range of values, rather than as a single absolute numerical point. The choice of method in Fuzzy AHP is related not only to the form of uncertainty representation but also to the priority derivation procedure and the defuzzification method. The extent analysis method introduced by Chang [
4] is relatively simple computationally but can result in zero weights for certain elements. As an alternative, the fuzzy geometric mean method developed by Buckley [
28] has a structure that is more consistent with the multiplicative characteristics of the pairwise comparison matrix. Furthermore, different defuzzification methods can yield different crisp values and priority orders. Therefore, the derivation and defuzzification procedures used must be explicitly stated so that the analysis results can be traced and reproduced.
Differences in weight derivation methods and forms of uncertainty representation can yield different rankings even when applied to the same problem [
29,
30]. Therefore, the choice of method should not be viewed as a neutral technical decision. Each approach involves a trade-off between computational efficiency, mathematical consistency, interpretability, and the ability to capture uncertainty. Furthermore, the ranking results must also be evaluated through sensitivity analysis to assess whether small changes in weights or model parameters can substantially alter the order of the alternatives. In the context of decision support system development, these conditions highlight the importance of a computational platform capable of providing multiple weight derivation methods, multiple consistency metrics, traceable convergence parameters, and transparent, reproducible analysis outputs. Such a platform serves not only as a computational tool but also as an analytical environment for comparing the methodological implications of each decision-making approach.
2.2. Multi Expert Aggregation and Group Decision Making
Multi-criteria decision-making applied in the real world rarely involves a single expert in assessing objectivity. Nearly all decisions today require a mathematically valid and socially acceptable collective agreement based on a panel of experts with diverse backgrounds and preferences. This section examines the four dimensions that shape the design space for multi-expert aggregation: the mathematical formulation of the aggregation procedure, the axiomatic properties that must be satisfied, the mechanisms for measurement and consensus-building, and the expert weighting scheme.
In the multi-expert aggregation process, Forman and Peniwati [
5] distinguishes two main approaches: Aggregation of Individual Judgments (AIJ) and Aggregation of Individual Priorities (AIP). AIJ combines pairwise comparison matrices before deriving priorities, whereas AIP aggregates individual priority vectors after each expert has completed the evaluation process. AIJ is more appropriate when the expert panel is treated as a single collective entity, while AIP is more appropriate when the autonomy of individual preferences needs to be preserved [
5,
31].
The choice between using the AIJ or AIP method is not a trivial matter. Simply put, AIJ assumes that the expert panel acts as a single entity representing the “organization,” while AIP preserves the individual autonomy of each expert, making it suitable for contexts where experts represent fundamentally different interests [
31]. The selection of an aggregation method must also be complemented by a mathematical operator that is ideal for combining these assessments, taking into account the axiomatic properties of that operator. Based on the study conducted, Aczél and Saaty [
12] states that the geometric mean is the only aggregation procedure capable of simultaneously satisfying three properties: reciprocity, unanimity, and homogeneity.
On the other hand, the arithmetic mean—which intuitively seems simple and reasonable—actually fundamentally violates the reciprocity property: for two ratings
a and
b, the arithmetic mean yields
, whereas the reciprocal is
unless
. Research findings indicate that the arithmetic mean can produce an aggregate matrix that lacks a priority vector consistent with the individual experts’ priority vectors, which constitutes a fundamental violation of the Pareto principle. Saaty and Vargas [
32] demonstrates that this violation theoretically manifests as the rank reversal phenomenon in practice. The theoretical claim above has been confirmed by extensive empirical evidence. Triantaphyllou [
13] experimentally demonstrated that AHP with arithmetic mean aggregation is susceptible to at least two types of rank reversal that do not occur in the multiplicative method
AHP using the geometric mean. The scope of this phenomenon is broader than expected; Maleki and Zahir [
14] conducted a systematic review of more than 80 studies reporting rank reversal and categorized them into seven main variants: (i) addition of identical alternatives, (ii) addition of non-identical alternatives, (iii) deletion of alternatives, (iv) addition of criteria, (v) removal of criteria, (vi) changes in the comparison matrix, and (vii) changes in the aggregation method. In addition to influencing the choice of operators, the characteristics of the expert panel also determine the optimal aggregation strategy.
Ossadnik et al. [
31] measured the relative sensitivity of AIJ and AIP to expert heterogeneity through Monte Carlo simulations and found that AIJ achieves higher aggregate consistency when inter-expert disagreement is low, while AIP is more stable when disagreement is substantial. The practical implications of these two findings converge on a single conclusion: the choice of aggregation operator and the choice of strategy (AIJ versus AIP) are interdependent on the characteristics of the expert panel; thus, practitioners require tools that support systematic exploration of combinations of both, rather than just a single fixed configuration. The discussion of expert disagreement in the previous section assumes that such disagreement can be objectively quantified. This measurement itself is a separate methodological issue that requires the selection of an appropriate metric. For two priority vectors
and
, the
disagreement index is defined in Equation (
1)
The equation above specifies generalization to
E experts via pairwise averages or via Euclidean and Chebyshev distance-based metrics [
33]. However, when disagreement exceeds an acceptable threshold, a formal mechanism is required to steer the panel toward consensus. Dong et al. [
11] proposes an iterative consensus model based on the row geometric mean prioritization method (RGMM), which at each iteration
t identifies the expert with the largest deviation from the current consensus
and suggests an adjustment to the rating as presented in Equation (
2)
Referring to the equation above,
is the convergence rate parameter, and the process continues until
for a predefined consensus threshold
. This approach has been extended in several directions; Altuzarra et al. [
34] proposes a Bayesian framework that treats each expert assessment as an observation with varying precision, Pedrycz and Song [
35] integrated information granularity allocation to optimize aggregation in the presence of substantial disagreement, and Bryson [
36] proposed a consensus measure based on the coefficient of variation that normalizes disagreement relative to the prior scale. These frameworks are conceptually complementary, but they are rarely implemented within a single computational tool; as a result, researchers who wish to compare their effectiveness on the same cases must currently code each method from scratch.
The entire discussion above regarding aggregation, axioms, and consensus relies on one assumption that has not yet been explicitly addressed: the weight of expert opinions. In practice, the assumption of equal weights (
) is often unrealistic because experts on a panel generally have varying levels of expertise, experience, and credibility. The literature offers two main approaches to this problem. Ramanathan and Ganesh [
37] proposes an intrinsic weighting approach in which expert weights are determined endogenously through peer-to-peer evaluation (experts evaluate each other’s competence), while Escobar and Moreno-Jiménez [
38] proposes an aggregation method that considers individual consistency as a proxy for the reliability of evaluations. Alternative exogenous approaches include weights based on organizational position, experience, or historical calibration against previous decisions [
5]. Despite these advances, several fundamental questions remain open: (i) how to detect and address strategic manipulation by experts who are aware of the weighting scheme, (ii) how to accommodate heterogeneous expertise where different experts excel at different sub-criteria, and (iii) how to link static aggregation decisions to the dynamics of expert learning over time [
11,
33,
39]. These questions, along with the previous discussion on operator selection, AIJ/AIP strategies, and consensus mechanisms, collectively require a computational infrastructure that enables systematic experimentation with combinations of weighting schemes, aggregation operators, and consensus mechanisms within a single integrated framework.
2.3. Existing Computational Tools
The previous subsections show that modern MCDA practice involves several methodological complexities, including multiple consistency metrics, competing fuzzy approaches, alternative aggregation strategies, heterogeneous expert panels, and unresolved questions regarding expert weighting. These issues raise an important question: to what extent do existing computational tools support systematic exploration of such methodological choices? This section reviews the current MCDA software landscape and identifies the gaps that motivated the development of ThinkDecision.
In the proprietary category, Expert Choice [
17] is one of the most established commercial implementations of AHP and ANP based on Saaty’s framework. It provides a mature graphical interface, support for complex hierarchical models, and extensive sensitivity analysis. However, its usefulness for academic and experimental research is constrained by high licensing costs, a closed-source architecture that limits methodological extension and reproducibility [
9], and the absence of a flexible API for integration with simulation pipelines or automated benchmarking.
SuperDecisions [
18] provides an important alternative, particularly for ANP modeling. It supports supermatrix structures and network-based decision models, making it a common reference tool in ANP studies. Nevertheless, its desktop-based and Windows-oriented architecture limits its use in distributed collaborative settings. Multi-expert collaboration depends largely on manual file exchange, which may create version conflicts and data inconsistencies. Moreover, native Fuzzy AHP support and standardized benchmarking facilities are not available. PriEsT [
19] is useful for teaching AHP because it implements several priority derivation methods, but it was designed primarily as a pedagogical tool rather than a platform for complex methodological experimentation.
Code-based alternatives exist in the R ecosystem. The “ahp” package [
20] supports standard AHP and basic sensitivity analysis, while “ahpsurvey” [
21] extends AHP to multi-respondent data. However, these packages do not support ANP supermatrix computation or Fuzzy AHP using triangular fuzzy numbers. Although “ahpsurvey” accommodates multiple experts, it does not explicitly implement the AIJ/AIP aggregation formalization proposed by Forman and Peniwati [
5], as expressed in Equations (
5) and (
7). Consequently, aggregation comparison, consensus updating, and robustness evaluation must be implemented manually.
Due to these limitations, many MCDA studies rely on ad-hoc scripts in MATLAB, Python, or R [
6,
16]. Although flexible, this practice reduces reproducibility, comparability, and extensibility because scripts are often study-specific, undocumented, and not publicly released. These issues have been identified as barriers to cumulative methodological progress [
16,
40]. As summarized in
Table 1, the main gap is the absence of an open-source, web-based platform that integrates AHP, ANP, and Fuzzy AHP with real-time multi-expert collaboration, consistency feedback, aggregation comparison, and systematic benchmarking. ThinkDecision was developed to address this gap.