Extension card · Picture
Picture fuzzy SAW
This is the form of SAW for situations where criterion scores come from a board's or a survey's yes-abstain-no vote distribution. This triple is carried through the calculation, and comes down to a single weighted score only in the last step.
Base method
SAW →
Philosophy, mechanics, strengths and weaknesses are on the base method card; this card describes only the difference.
Data type (family)
Picture →
What this data type is, when to use it, how to write it in a cell: the family's full account is here.
What Changes from the Base Method?
Cells. In crisp SAW every cell holds a single number. Here every cell holds three degrees: support (yes, μ), abstention (η), and rejection (no, ν); their sum cannot exceed 1. This triple comes from a board's or a survey's vote distribution on the same judgement. Criterion weights are taken from outside, as crisp numbers.
Scale equalisation. Crisp SAW first divides every column by its own magnitude. There is no column-based division in this family; picture fuzzy triples are already a structure between 0 and 1. Instead, in a cost criterion, support and rejection swap places while the abstention degree stays as it is: (μ, η, ν) → (ν, η, μ).
Weighted sum and defuzzification. Crisp SAW weights every column and sums it directly. Here, all the criteria that have been brought to the "higher is better" direction are reduced, in a single operation, directly to one aggregate triple through a picture fuzzy weighted aggregation (PFWA): μ_i = 1−∏(1−μ_ij)^{w_j}, η_i = ∏η_ij^{w_j}, ν_i = ∏ν_ij^{w_j}. The weights are used exponentially inside this aggregation; there is no separate column normalisation as in crisp SAW. Only at this last step is the aggregate triple reduced to a single number with Garg's (2017) score function (s = μ − η − ν); in the event of a tie, the alternative with the lower accuracy measure H = μ + η + ν is placed ahead.
DecisionMind fixes, in classic picture fuzzy SAW, the PFWA aggregation, the Garg score function (μ−η−ν), and the H-based tie-breaking rule. Weights are taken from outside as crisp numbers; the method does not generate weights.
How to Read the Output
The score is read like crisp SAW's total score; it only ranks this set of alternatives, and is not a percentage or a probability.
The difference is this. The score subtracts all three of μ, η and ν together, giving a value between −1 and 1; the abstention share (η) is a component that pulls the score towards the negative, and it is not as visible as support. Two alternatives can reach the same score, one from low rejection, the other from high abstention.
Thus instead of writing:
"This alternative is definitely the best because its picture fuzzy SAW score comes out highest"
the report should read:
"This score is the support-minus-abstention-minus-rejection difference emerging from the weighted aggregation of the vote distribution; which alternative carries the larger abstention share, that is, how 'open' the decision remains, should be shown separately"
When to Prefer This over the Base Method
Use this extension when criterion assessments come from a board's, a survey's, or a panel's yes, abstain, no vote distribution on the same judgement; for that, the three shares must be separately countable. Inventing the other two degrees from a single support percentage erases this extension's one contribution; the detail is on the Picture Fuzzy data-type card. There is no need to expand a measured criterion (such as price or time) into a picture fuzzy triple. The exit condition is the same as for crisp SAW: if no concession is acceptable on a criterion, this extension is compensatory too, and will not eliminate anything below a threshold.
Mistakes Specific to This Extension
Value-space violation. In every cell, the sum μ+η+ν must not exceed 1; this must be checked before aggregation.
Inventing a triple from a single proportion. Saying "there is 60 per cent support, so 40 per cent is opposed" sets the abstention share to zero; every degree must be counted separately.
Computing the score as μ−ν and skipping η. In this engine the score uses all three degrees at once (μ−η−ν); leaving the abstention share out can produce a different, incorrect ranking.
Defuzzifying first and then running crisp SAW. Taking every cell's support ratio alone and applying the crisp method is not this extension; the abstention and opposing-vote information is erased in the first step.
The governing principle is this:
Picture fuzzy SAW exists to carry a board's or a survey's abstention share through to the construction of the aggregate triple. Any application that invents a degree or crispens the input from the outset erases this contribution.
Cases
The first case is DecisionMind's validation example; the manifest's synthetic 3×3 table is built faithfully to Garg's (2017) PF-MCDM pattern (cost completion, PFWA aggregation, score), but with simplified figures, and carries no page reference in the literature. The second case is an illustrative fiction.
1. Illustrative example (DecisionMind's validation example): Choosing a new product concept
A company board is to decide which of three new product concepts to develop. There are three criteria: market potential (higher is better), technical feasibility (higher is better), development cost (lower is better). Board members have cast yes, abstain, no votes separately for every concept-criterion pair.
| Concept | Market potential | Technical feasibility | Development cost (lower is better) |
|---|---|---|---|
| Ü1 | (0.40; 0.30; 0.20) | (0.50; 0.20; 0.20) | (0.20; 0.30; 0.40) |
| Ü2 | (0.60; 0.20; 0.10) | (0.30; 0.30; 0.30) | (0.40; 0.20; 0.30) |
| Ü3 | (0.50; 0.20; 0.20) | (0.40; 0.20; 0.30) | (0.30; 0.20; 0.40) |
| Weight | 0.50 | 0.30 | 0.20 |
The method swaps support and rejection in development cost, merges the triples of the three criteria with PFWA, and computes the score (μ−η−ν).
| Concept | Score | Rank |
|---|---|---|
| Ü2 | 0.0615 | 1 |
| Ü3 | 0.0073 | 2 |
| Ü1 | −0.0337 | 3 |
The result reads as follows. Ü2 has the highest support vote (0.60) and the lowest rejection vote (0.10) on market potential, the most heavily weighted criterion; this advantage compensates for its middling performance on the other criteria. Ü1 comes last because it has the lowest support vote on market potential.
The board's hesitation is this: what happens if market potential's weight is lowered from 0.50 to 0.20 and development cost is given 0.65? As confirmed by an independent Python calculation, when the weights are redistributed to (0.20; 0.15; 0.65), Ü3's score drops to −0.0551 and Ü2's to −0.1288; first place passes to Ü3, because Ü3's low rejection vote on development cost now determines the heaviest criterion.
In the report: "With the given weights (0.50; 0.30; 0.20), Ü2 has the highest score (0.0615). When the weight is markedly shifted to development cost (0.20; 0.15; 0.65), first place passes to Ü3; which criterion takes priority in the board's decision should therefore be justified separately."
Source: DecisionMind's PIF-SAW validation example; it is built faithfully to the formula chain of Garg's (2017) published PF-MCDM pattern (Section 4, Steps 1-5), but with simplified, hand-traceable figures, and the paper's own decision table has not been used in this card. The value space rests on Cuong and Kreinovich's (2013) definition of the picture fuzzy set. The scores and the weight-trade-off scenario have been computed independently by this card's author by running the kernel directly.
2. Freight: An e-commerce company's choice of last-mile delivery vehicle
An e-commerce company is to choose one of three vehicle models for its last-mile delivery fleet. There are three criteria: delivery capacity and speed (higher is better), urban manoeuvrability (higher is better), and operating and fuel expense (lower is better). The logistics and fleet-management teams have reported yes, abstain, no votes separately for every vehicle-criterion pair.
The method swaps support and rejection in operating expense, merges the triples of the three criteria with PFWA, and scores them. Suppose the vehicle with the highest delivery capacity also turns out to have a low rejection vote on manoeuvrability, and comes out first.
The company's hesitation is this: the abstention share on operating expense, that is, the fleet-management members who gave no clear opinion on this, has dissolved into the score. Before the vehicle is added to the fleet, the source of this uncertainty (a maintenance-cost estimate, for instance) should be clarified; looking at the score alone conceals this uncertainty.
In the report: "One vehicle stands out because of its delivery capacity and manoeuvrability; the abstention vote share within the team on operating expense is high, and the fleet decision should not be finalised before the cost estimate is clarified."
3. What Not to Do
If development cost had been marked "higher is better" in the illustrative example, the most expensive concept would receive full support on this criterion, and Ü2's low-cost advantage would be reversed. The second error is inventing Ü1's market-potential triple (0.40; 0.30; 0.20) from a single support ratio ("40 per cent support, so 60 per cent opposed") and disregarding the abstention share. The third error is reporting Ü2's score of 0.0615 as "the board's definite preference"; the score only ranks these three concepts relative to each other, and conceals the abstention shares.
Sources
For the formulas behind each step, the intermediate tables and citation formats, see the DecisionMind method page: decisionmind.app/library/pif-saw
Fishburn, P. C. (1967). Additive utilities with incomplete product sets: Application to priorities and assignments. Operations Research, 15(3), 537–542. DOI: 10.1287/opre.15.3.537
Cuong, B. C., & Kreinovich, V. (2013). Picture fuzzy sets – A new concept for computational intelligence problems. 2013 Third World Congress on Information and Communication Technologies (WICT 2013), 1–6. DOI: 10.1109/WICT.2013.7113099
Cuong, B. C. (2014). Picture fuzzy sets. Journal of Computer Science and Cybernetics, 30(4), 409–420. DOI: 10.15625/1813-9663/30/4/5032
Garg, H. (2017). Some picture fuzzy aggregation operators and their applications to multicriteria decision-making. Arabian Journal for Science and Engineering, 42(12), 5275–5290. DOI: 10.1007/s13369-017-2625-9