Journal of Applied Mathematics

Volume 2013, Article ID 705159, 24 pages

http://dx.doi.org/10.1155/2013/705159

## Some Generalized Dependent Aggregation Operators with Interval-Valued Intuitionistic Fuzzy Information and Their Application to Exploitation Investment Evaluation

^{1}School of Management, Hefei University of Technology, Hefei 230009, China^{2}Key Laboratory of Process Optimization and Intelligent Decision-Making, Ministry of Education, Hefei 230009, China^{3}School of Economics and Management, Zhejiang Normal University, Jinhua 321004, China

Received 28 January 2013; Accepted 21 April 2013

Academic Editor: Francisco Chiclana

Copyright © 2013 Xiao-wen Qi et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

#### Abstract

We investigate multiple attribute group decision making (MAGDM) problems with arguments taking the form of interval-valued intuitionistic fuzzy numbers. In order to relieve influence of unfair arguments, a Gaussian distribution-based argument-dependent weighting method and a hybrid support-function-based argument-dependent weighting method are devised by, respectively, measuring support degrees of arguments indirectly and directly, based on which the Gaussian generalized interval-valued intuitionistic fuzzy ordered weighted averaging operator (Gaussian-GIIFOWA) and geometric operator (Gaussian-GIIFOWG), the power generalized interval-valued intuitionistic fuzzy ordered weighted averaging (P-GIIFOWA) operator and geometric (P-GIIFOWA) operator are proposed to generalize a wide range of aggregation operators for decision makers to flexibly choose in decision modelling. And some desirable properties of the proposed operators are also analyzed. Further, application of an approach integrating proposed operators to exploitation investment evaluation of tourist spots has shown the effectiveness and practicality of developed methods; experimental results also verify the properties of proposed operators.

#### 1. Introduction

Multiple attribute group decision making (MAGDM) is an important part of decision theories and the purpose of MAGDM is to find a desirable solution from finite alternatives by a group of experts assessing on multiple attributes with different types of decision information, such as crisp numbers [1–5], interval values [6–8], linguistic scales [9–11], and fuzzy numbers [12–17]. In order to better handle the fuzziness and uncertainty in decision process, intuitionistic fuzzy set (IFS) [18] and interval-valued intuitionistic fuzzy set (IVIFS) [19] have been introduced and increasing approaches [20–31] for MAGDM with intuitionistic fuzzy information can be found in related research literatures. Among the procedures of those MAGDM approaches, a very common information aggregation technique is the OWA [32] operator, which can provide a parameterized family of aggregation operators including the maximum, the minimum, and the average criteria. Since its appearance, the OWA operator has been developed and used in a wide range of applications in decision making and expert systems [8, 10, 13, 21–24, 33–40].

The important and fundamental step of OWA operator and its extended versions is to determine the associated weights. Many researches have been carried out on this issue and useful methods have been developed under different decision environments, such as crisp numbers, interval numbers, and linguistic scales, which can be mainly classified into two categories [41]: (1) argument-independent approaches [42–48]; (2) argument-dependent approaches [4, 5, 9, 11, 23, 41, 42, 44, 45, 49–52]. The weights derived by the argument-independent approaches are associated with particular ordered positions of the aggregated arguments and have no connection with the aggregated arguments, while the argument-dependent approaches determine the weights based on input arguments. As for the argument-dependent approaches, the prominent characteristic is that they can relieve the influence of unfair arguments on the aggregated results by assigning low weights to those “false” and “biased” ones. In viewing of this merit, researches on argument-dependent approaches under intuitionistic fuzzy environments and interval-valued intuitionistic fuzzy environments have started to accumulate recently, such as the linear programming-based aggregation operators with partial weight information [53], the aggregation operators [24] based on power method [54], the induced aggregation operators [55] based on Choquet integral and Dempster-Shafer theory, the power average operators [27] with trapezoidal intuitionistic fuzzy information, the generalized intuitionistic fuzzy power averaging operators [23], and the generalized dependent aggregation operators [40] for MAGDM with intuitionistic linguistic information.

Another practical and interesting research issue of applying OWA operator to MAGDM is the generalized extensions utilizing generalized means and quasiarithmetic means, which are, respectively, known as the generalized OWA (GOWA) operators [35, 56] and the Quasi-OWA operators [57]. And the main advantages of generalized operators are that they can generalize a wide range of aggregation operators including the average, the OWA and the OWG operators, and that they can flexibly reflect the interests and actual needs of decision makers, such as the generalized extensions [58] of induced OWA (IOWA) operator [59], the generalized weighted exponential proportional aggregation operators [4] for group decision making with crisp numbers, the expanded generalized hybrid averaging (GHA) operator [37, 60] for fuzzy multiattribute decision making environments, the induced linguistic generalized OWA (ILGOWA) operators [61], and the generalized power aggregation operators for linguistic environment [9].

As for the decision making situations with intuitionistic fuzzy information, several researches have been conducted to address suitable generalized operators recently. Zhao et al. [62] investigated extensions of GOWA operator to present the generalized intuitionistic fuzzy weighted averaging operator, generalized intuitionistic fuzzy ordered weighted averaging operator, generalized intuitionistic fuzzy hybrid averaging operator, and Li [36] presented another extensions of GOWA operator to accommodate intuitionistic fuzzy information. However, all the above operators are unsuitable for aggregating individual preference relations into group preference relation when some experts prefer to aggregate the variables with an inducing order. So, Xu and Xia [55] studied the induced generalized intuitionistic fuzzy Choquet integral operators and induced generalized intuitionistic fuzzy Dempster-Shafer operators. Xu and Wang [22] developed the induced generalized intuitionistic fuzzy ordered weighted averaging (IGIFOWA) operator based on the GIFOWA [62] and the I-IFOWA [22, 63] operators. And based on the IGOWA operator introduced by Merigó and Gil-Lafuente [58], Su et al. [21] presented another induced intuitionistic generalized fuzzy ordered weighted averaging (IG-IFOWA) operator. In addition, Zhou et al. [23] proposed a generalized operator based on the power aggregation operator and generalized mean, but the same as most researches [9, 11, 24, 38, 64] that focused on extended power aggregation operators, they did not discuss construction methodology of support function in their presented operators. Comparatively, current research on generalized operators for decision making situations with interval-valued intuitionistic fuzzy information is still in its infancy; only few papers can be found in the literature. Representatively, Zhao et al. [62] further extended the GOWA operators to present some basic generalized aggregation operators for dealing with interval-valued intuitionistic fuzzy information, including the generalized interval-valued intuitionistic fuzzy weighted averaging operator, generalized interval-valued intuitionistic fuzzy ordered weighted averaging operator, and generalized interval-valued intuitionistic fuzzy hybrid average operator. Based on the Choquet integral method and Dempster-Shafer theory, Xu and Xia [55] investigated patulous induced generalized operators for aggregation of interval-valued intuitionistic fuzzy information. And most recently, Xu and Wang [22] also studied the induced version of generalized OWA operators for interval-valued intuitionistic fuzzy group decision making.

The aim of this paper is to develop some generalized argument-dependent aggregation operators more suitable for tackling with uncertainty in multiple attribute group decision making with interval-valued intuitionistic fuzzy information. Inspired by the Gaussian distribution method, we present the Gaussian generalized interval-valued intuitionistic fuzzy ordered weighted averaging (Gaussian-GIIFOWA) operator and Gaussian generalized interval-valued intuitionistic fuzzy ordered weighted geometric (Gaussian-GIIFOWG) operator; and a hybrid method is developed for construction of support degree function, based on which we further present the power generalized interval-valued intuitionistic fuzzy ordered weighted averaging (P-GIIFOWA) operator and the power generalized interval-valued intuitionistic fuzzy ordered weighted geometric (P-GIIFOWG) operator. The main advantages of these operators are that: they depend on input arguments neatly and allow arguments being aggregated to support each other so that they can relieve the influence of unfair assessments on decision results by assigning low weights to those “false” and “biased” ones; and simultaneously they can include a wide range of aggregation operators as particular cases, such as interval-valued intuitionistic fuzzy averaging (IIFA) operator, interval-valued intuitionistic fuzzy geometric (IIFG) operator, Gaussian interval-valued intuitionistic fuzzy ordered weighted geometric (Gaussian-IIFOWG) operator and averaging (Gaussian-IIFOWA) operator, power interval-valued intuitionistic fuzzy ordered weighted geometric (P-IIFOWG) operator and averaging (Gaussian-IIFOWA) operator, and generalized IIFA (GIIFA) operator and generalized IIFG (GIIFG) operator. Furthermore, an approach based on the proposed operators is developed and applied to solve a practical MAGDM problem concerning exploitation investment evaluation of tourist spots. This approach can give a more completely view of decision problems with decision information aggregation depending on input arguments and can also be suitable for solving other group decision making problems including supplier selection decision making, strategic management decision making, human resource management, and emergency solutions evaluation.

The remainder of this paper is organized as follows. In Section 2, we give a concise review of fundamental concepts related to intuitionistic fuzzy sets and interval-valued intuitionistic fuzzy sets. In Section 3, we first introduce some related basic aggregation operators, and then we present two methods to obtain argument-dependent attribute weights by Gaussian distribution method and by support degree function, respectively, based on which the Gaussian-GIIFOWA operator, Gaussian-GIIFOWG operator, P-GIIFOWA operator, and P-GIIFOWG operator are presented. In addition, some desirable properties of these operators are analyzed. In Section 4, an approach for multiple attribute group decision making under interval-valued intuitionistic fuzzy environments is constructed based on the four generalized dependent aggregation operators. In Section 5, application study on exploitation investment evaluation of tourist spots is conducted to verify the validity and practicality of developed methods. Finally, conclusions are given in Section 6.

#### 2. Preliminaries

In this section, we briefly review some basic concepts to facilitate future discussions.

Atanassov [18] generalized the concept of fuzzy set and defined the concept of intuitionistic fuzzy set as shown in the following Definition 1.

*Definition 1 (see [18]). *An intuitionistic fuzzy set (IFS) is a generalized fuzzy set and can be defined as
in which means a membership function and means a nonmembership function, with the condition , , for all . Particularly, ; the given IFS is degraded to an ordinary fuzzy set.

In reality, it may not be easy to identify the exact values for the membership and nonmembership degrees of an element a set. In this case, a range of values should be a more appropriate measurement to accommodate the vagueness. So, Atanassov and Gargov [19] introduced the notion of interval-valued intuitionistic fuzzy set (IVIFS).

*Definition 2 (see [19]). *An interval-valued intuitionistic fuzzy set (IVIFS) in can be defined as
where , , for all .

Similarly, the intervals and denote the membership and non-membership of an element a set.

If each of the intervals and contains only one value for each , we have

Then, the given IVIFS is degraded to an ordinary IFS.

In order to aggregate interval-valued intuitionistic fuzzy information, Xu [65] defined the following relations and basic operations.

*Definition 3 (see [65]). *Let , , be interval-valued intuitionistic fuzzy numbers (IVIFNs), then(1);(2);(3);(4).

Usually, the following normalized distance measure formulae listed in Definition 4 can be introduced to calculate the distance of IVIFSs.

*Definition 4. *Suppose that two interval-valued intuitionistic fuzzy sets (IVIFSs) and in can be defined as
then we can have(1)the normalized Euclidean distance measure:
(2)the normalized Hamming distance measure:
(3)the normalized Hausdorff distance measure:

In order to rank alternatives, it is necessary to consider how to compare two interval-valued intuitionistic fuzzy numbers, so Xu [66] devised an approach to compare two IVIFNs based on the concepts of score function and accuracy function.

*Definition 5 (see [66]). *For any three IVIFNs , , and , score function can be defined as , accuracy function can be defined as , and if , then is smaller than , ; if , then is greater than , ; if , then if , then is smaller than , ; if , then is greater than , ; if , then and represent the same information, denoted by .

#### 3. Proposed Generalized Dependent Interval-Valued Intuitionistic Fuzzy Ordered Weighted Aggregation Operators

##### 3.1. Basic Operators

Up to now, some useful operators have been proposed for aggregating the interval-valued intuitionistic fuzzy information. The most commonly used two operators for aggregating interval-valued intuitionistic fuzzy arguments are the interval-valued intuitionistic fuzzy weighted averaging (IIFWA) operator and geometric (IIFWG) operator as defined by Xu [65] in the following definitions.

*Definition 6 (see [65]). *An interval-valued intuitionistic fuzzy weighted averaging (IIFWA) operator of dimension is a mapping IIFWA: , which has an argument associated vector with and , such that

Let be a collection of interval-valued intuitionistic fuzzy numbers, then their aggregated value by using the IIFWA operator can be shown as

Particularly, when , the IIFWA operator reduces to the interval-valued intuitionistic fuzzy averaging (IIFA) operator; that is,

*Definition 7 (see [65]). * An interval-valued intuitionistic fuzzy weighted geometric (IIFWG) operator of dimension is a mapping IIFWG: , which has an argument associated vector with and , such that

Particularly, when , the IIFWG operator reduces to the interval-valued intuitionistic fuzzy geometric (IIFG) operator; that is,

Considering ordered positions of interval-valued intuitionistic fuzzy arguments rather than weighting the interval-valued intuitionistic fuzzy arguments themselves, Xu and Chen [67] proposed an interval-valued intuitionistic fuzzy ordered weighted averaging (IIFOWA) operator and an interval-valued intuitionistic fuzzy ordered weighted geometric (IIFOWG) operator, as shown in the following definitions.

*Definition 8 (see [67]). *Let be a collection of interval-valued intuitionistic fuzzy arguments, and . The interval-valued intuitionistic fuzzy ordered weighted averaging (IIFOWA) operator of dimension is a mapping IIFOWA: , which has an associated weight vector , and ; then
where is a permutation of , with for all .

Particularly, when , the IIFOWA operator reduces to the IIFA operator; that is,

*Definition 9 (see [67]). *Let be a collection of interval-valued intuitionistic fuzzy arguments, and . The IIFOWG operator of dimension is a mapping IIFOWG: , which has an associated weight vector , and ; then
where is a permutation of , with for all .

Particularly, when , the IIFOWG operator reduces to the IIFG operator; that is,

From another important and practical aspect, Yager [56] defined a generalized version of OWA operators as the generalized ordered weighted averaging (GOWA) operator; then Zhao et al. [62] extended it to the situations where input arguments are IVIFNs and presented a generalized interval-valued intuitionistic fuzzy ordered weighted averaging (GIIFOWA) operator and geometric (GIIFOWG) operator as defined in Definitions 10 and 11.

*Definition 10 (see [62]). *Let be a collection of interval-valued intuitionistic fuzzy arguments, and . The GIIFOWA operator of dimension is a mapping GIIFOWA: , which has an associated weight vector , and , ; then
where is a permutation of , with for all .

If , then the GIIFOWA operator reduces to the GIIFA operator; that is,

*Definition 11 (see [62]). *Let be a collection of interval-valued intuitionistic fuzzy arguments, and . The GIIFOWG operator of dimension is a mapping GIIFOWG: , which has an associated weight vector , and , ; then
where is a permutation of , with for all .

If , then the GIIFOWG operator reduces to the GIIFG operator; that is,

From Definition 8 to Definition 11, it can be seen that one important and basic step of interval-valued intuitionistic fuzzy ordered weighted aggregation operators and generalized versions is to determine the associated weights. In the following subsections, we will focus on investigating argument-dependent operators in which the associated weights can be determined objectively only depending on the interval-valued intuitionistic fuzzy input arguments.

##### 3.2. Proposed Gaussian Generalized Interval-Valued Intuitionistic Fuzzy Aggregation Operators

According to the basic operational rules listed in Definition 3 and IIFWA operator in Definition 6 for aggregating IVIFNs, here we can naturally define mean value of a set of IVIFNs as shown in the following definition. Obviously, the mean value is still an IVIFN.

*Definition 12. *Let be a collection of interval-valued intuitionistic fuzzy arguments, where . Let be the mean value of , and ; then can be obtained by IIFWA operator with , where

*Definition 13 (see [68]). *Let be a collection of interval-valued intuitionistic fuzzy arguments, and . denotes mean value of ; then the variance of can be computed according to

In real world, a collection of aggregated arguments usually takes the form of a collection of preference values provided by different decision makers. Some decision makers may assign unduly high or unduly low preference values to their preferred or repugnant objects. In such case, very low weights should be assigned to these “false” or “biased” opinions; that is to say, the closer a preference value argument is to the mid one(s), the more the weight; conversely, the further a preference value is apart from the mid one(s), the less the weight. So, Xu [44] and Xu [49] developed Gaussian (normal) distribution-based method to determine OWA weights by utilizing orderings of arguments assessed with crisp numbers and interval numbers, respectively. Inspired by these ideas, by using predefined mean value of IVIFNs, we extended the Gaussian distribution method to obtain the dependent weights, here called Gaussian weighting vector, according to interval-valued intuitionistic fuzzy input arguments.

*Definition 14. *Let be the mean value of given interval-valued intuitionistic fuzzy arguments, the variance of given interval-valued intuitionistic fuzzy arguments; then the Gaussian weighting vector can be defined as
where is a permutation of (), with for all .

Consider that and are commonly required in aggregation operators; then we can normalize the Gaussian weighting vector according to

Then by (17), we can define a Gaussian generalized interval-valued intuitionistic fuzzy ordered weighted averaging (Gaussian-GIIFOWA) operator, as shown in the following definition.

*Definition 15. *A Gaussian-GIIFOWA operator of dimension is a mapping Gaussian-GIIFOWA: , which has an associated Gaussian weighting vector , with and ; then
where is a permutation of , with for all .

Similarly, we can define the Gaussian generalized interval-valued intuitionistic fuzzy ordered weighted geometric (Gaussian-GIIFOWG) operator.

*Definition 16. *A Gaussian-GIIFOWG operator of dimension is a mapping Gaussian-GIIFOWG: , which has an associated Gaussian weighting vector with and ; thenwhere is a permutation of with for all .

Let , ; then by Definition 3, Gaussian-GIIFOWA operator and Gaussian-GIIFOWG operator can be transformed into the following forms;then we can rewrite as

Obviously, the aggregated results of Gaussian-GIIFOWA operator and Gaussian-GIIFOWG operator are independent of orderings; thus, Gaussian-GIIFOWA and Gaussian-GIIFOWG are neat and dependent operators.

Theorem 17. *Let be a collection of interval-valued intuitionistic fuzzy arguments, and the be the Gaussian weighting vector related to Gaussian-GIIFOWA operator and Gaussian-GIIFOWG operator, with and ; then Gaussian-GIIFOWA operator and Gaussian-GIIFOWG operator have the following properties.*(1)*Commutativity: let be any a permutation of ; then
*(2)*Idempotency: let , for all ; then
*(3)*Boundedness: the Gaussian-GIIFOWA operator and the Gaussian-GIIFOWG operator lie between the max and min operators;
**where
*

Theorem 18. *Let , be two collections of interval-valued intuitionistic fuzzy arguments, a permutation of with for all , and the Gaussian weighting vector related to the Gaussian-GIIFOWA operator and Gaussian-GIIFOWG operator, with and ; then * *(1) if , then the Gaussian-GIIFOWA operator and Gaussian-GIIFOWG operator reduce to the following Gaussian-IIFOWA operator and Gaussian-IIFOWG operator:*

*(2) if **, then the Gaussian-GIIFOWA operator reduces to the Gaussian-IIFOWG operator; * *(3) if **, then the Gaussian-GIIFOWA operator and Gaussian-GIIFOWG operator reduce to the GIIFA operator and GIIFG operator;* *(4) if ** and **, then the Gaussian-GIIFOWA operator and Gaussian-GIIFOWG operator reduce to the IIFA operator and IIFG operator;* *(5) if ** and **, then the Gaussian-GIIFOWA operator reduces to the IIFG operator.*

Lemma 19. *Assume that , , , and , then
**
with equality if and only if . *

Theorem 20. *Let , be two collections of interval-valued intuitionistic fuzzy arguments, is a permutation of with for all , and let be the Gaussian weighting vector related to the Gaussian-GIIFOWA operator and Gaussian-GIIFOWG operator, with and , then *(1)*; *(2)*;*(3)*. *

*Proof. *Based on Lemma 19, we can have