Generalized intuitionistic fuzzy soft sets with applications in decision-making
Introduction
The concept of intuitionistic fuzzy set (IFS) [1], [2] extends a fuzzy set by having an additional hesitancy parameter besides the usual membership function. The hesitancy parameter makes IFS useful in modeling many real life activities like evaluation, negotiation and decision making where judgments of human beings play a major role. Molodtsov [3] has pointed out that both the fuzzy set and intuitionistic fuzzy set theories suffer from the inherent difficulty that the magnitude of membership grade for x given by an individual is directly dependent on the knowledge available to the individual; hence prone to variations. Moreover, both the fuzzy and intuitionistic fuzzy theories lack an appropriate parameterization tool. The theory of soft sets addresses these limitations [3].
The soft set theory is based on adequate parameterization. The description of objects is more comprehensive in the soft set theory than in the fuzzy and the intuitionistic fuzzy theories. One can have any number of attributes/parameters in the description of an object in the soft set theory. This makes it easier to compare the objects in terms of the attributes thereby permitting the decision making even with partial information. In view of this, the soft set theory has found several applications in multi-criteria decision making [8], [17].
Maji et al. [4], [5], [6] have combined the soft set theory with the intuitionistic fuzzy set theory to come up with the concept of intuitionistic fuzzy soft set (IFSS). The parameterization and hesitancy accrued to IFSS from this combination facilitate the descriptions of the real-world situations quite accurately. In particular, IFSS is extremely useful in multi-criteria decision making (MCDM) problems where the evaluation of alternatives is done by experts based on the attributes. The suitability of IFSS for the decision making applications is aptly highlighted in [7], [8].
The MCDM model in an IFSS environment takes into account the hesitancy of experts in arriving at the membership grades since the IFS allows an expert to record his hesitancy factor. However, hesitancy is a feature of one's own perception, and it needs to be supported by another independent observer/expert. To address this problem, the notion of generalized intuitionistic fuzzy soft set (GIFSS) is introduced in [25] and developed independently in [26], [27]. The framework of GIFSS requires the moderator's assessment of the credibility of the information in the original IFSS so as to make up for any distortion in the information provided.
In this paper, we further extend the concept of GIFSS by introducing a generalization parameter which itself is intuitionistic fuzzy. We also develop the relations on GIFSS, termed as generalized intuitionistic fuzzy soft relations (GIFSR). A score function and a similarity measure are devised for the comparison of two intuitionistic fuzzy numbers and two GIFSSs respectively. The suitability of GIFSS in supplier selection and medical diagnosis problems is examined by taking up case studies from the real world.
In our view, it is hard to make accurate decisions on the basis of the individuals’ vague conceptions. The GIFSS attempts to minimize the possibility of errors caused by the imprecise information by taking the moderator's opinion on the same. For example, a patient might exaggerate the symptoms which may lead to incorrect diagnosis. The specialist may not have enough time to ascertain the information supplied by probing the patient in detail. It may be more judicious to have a junior doctor moderate the severity of the symptoms of a patient through a generalization parameter.
The GIFSS has a wide scope in the areas like economics, supply chain management, financial accounting and medical expert systems. For an example, in the current medical practice, a specialist diagnoses a patient simply going by the symptoms reported. Similarly the decisions related to the supplier selection problems are based solely upon the evaluation of the suppliers by the domain experts. In such decision making problems, the possibility of error in the judgment (of a patient about the severity of his symptom or of the domain experts in the evaluation of a supplier with respect to a criterion) cannot be ruled out. The potential of the proposed framework in addressing this issue will be demonstrated on a few case-studies. The expert systems deploying the GIFSS would obviate the risk of serious errors in the decision-making.
The paper is organized as follows. Section 2 discusses a few preliminaries and useful definitions related to IFS and IFSS. Section 3 introduces GIFSS and presents its properties. A novel score function and a similarity measure for comparison of two GIFSSs are provided in Section 4. Section 5 is concerned with the concept of generalized intuitionistic fuzzy relations (GIFSR) on GIFSS and its relevant properties. Section 6 presents an approach based on GIFSS to solve the supplier selection problem. A real case study involving supplier selection problem is given in this section. Section 7 shows the utility of the GIFSS in the decision making by solving two supplier selection problems using the similarity measure, proposed in Section 4. An application of generalized intuitionistic fuzzy relations (GIFSR) in solving a medical diagnosis problem is shown in Section 8. Finally, Section 9 gives conclusions of this paper.
Section snippets
Multi-criteria decision making with intuitionistic fuzzy techniques
Fuzzy logic has become an inevitable part of multi criteria decision making because of the need to represent the associated uncertainty. To cater to the increased role of fuzzy logic, fuzzy sets have been extended in the literature leading to type-2 fuzzy sets [28], interval type-2 fuzzy sets [29], vague sets [30], probabilistic fuzzy sets [31], fuzzy soft sets [5] and intuitionistic fuzzy sets [1]. Recently, intuitionistic fuzzy sets have attracted considerable attention in the fuzzy decision
Generalized intuitionistic fuzzy soft set (GIFSS)
With the advent of GIFSS, the evaluation of an alternative against the criteria in an IFSS is moderated with the generalization parameter. The moderated input information can really go a long way in improving the current expert systems by ensuring a higher accuracy in the final decisions. Without moderation, the original evaluation remains uncertified; this means that the veracity of the assessment is doubtful.
In this section, we present the definitions of GIFSS and illustrate it through
Score function and similarity measure in GIFSS
In several areas such as pattern recognition, image processing, region extraction and coding theory, there is a need to compare two fuzzy numbers. A novel score function is devised here to compare two intuitionistic fuzzy numbers (IFNs). A similarity measure to compare two GIFSSs is also proposed.
Relations on GIFSS
The notion of intuitionistic fuzzy soft relation (IFSR) is generalized to GIFSR in the context of GIFSS. The concept of GIFSR is illustrated through simple examples and the properties of GIFSR are investigated in detail. Definition 5.1 An intuitionistic fuzzy soft relation (IFSR) between two IFSSs, and over soft universes (U, E) and (U, D) respectively, is defined [10] as: Definition 5.2 A
Supplier selection using GIFSS
Selection of the best supplier is of utmost importance for the success of an organization because of the impact of the decisions made on cost, manufacturing, service, efficiency and overall satisfaction of the customers. It is often a difficult decision to select the best supplier as multiple criteria are involved and these are often conflicting. The importance of supplier selection for the businesses is also testified by the numerous studies in the literature [18], [19], [20], [21]. In the
Two case studies based upon similarity measure of GIFSS
The potential of GIFSS is further highlighted through two case-studies that use the similarity measure discussed in Section 4. The case-studies deal with finding the best supplier.
An application of GIFSS and GIFSR for medical diagnosis
GIFSS can be effectively used to reduce the errors encountered in medical diagnosis. These errors often turn out to be quite serious to the victims. The World Health Organization (WHO) recognizes medical errors as having fatal consequences on the patients. As reported by WHO, one in 10 hospital admissions involves an error and one in 300 admissions results in death due to wrong diagnosis. This claim is also reinforced by the British National Health System survey in 2009 [35] which reports that
Conclusions
This paper extends the Intutionisitc Fuzzy Soft Sets (IFSS) to the Generalized IFSS (GIFSS) by introducing the generalization parameter to the pool of the intutionistic fuzzy numbers (IFNs) of IFSS. The generalization parameter is a kind of the moderator's assessment on the presented information as IFNs. The role of moderator is to refine IFNs with his domain specific knowledge. It may be noted that the information of any sort often gets misinterpreted during its presentation. This usually
Acknowledgments
The help rendered by Mr. R. K. Vishwakarma, I.G., CRPF, India in procuring the data for Case-study 1 is gratefully acknowledged. The authors also express their indebtedness to the anonymous reviewers for their suggestions that have led to an improved version of this paper.
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