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Mathematica Moravica Vol. 19-2 (2015), 35–48 An Introduction to Fuzzy Soft Graph Sumit Mohinta and T.K. Samanta Abstract. The notions of fuzzy soft graph, union, intersection of two fuzzy soft graphs are introduced in this paper and a few properties relat- ing to finite union and intersection of fuzzy soft graphs are established here. 1. Introduction In 1999, D.Molodtsov[4] introduced the notion of soft set theory to solve imprecise problems in economics, engineering and environment. He has shown several applications of this theory in solving many practical prob- lems. There are many theories like theory of probability, theory of fuzzy sets, theory of intuitionistic fuzzy sets, theory of rough sets, etc. which can be considered as mathematical tools to deal with uncertainties. But all these theories have their own inherent difficulties. The theory of probabilities can deal only with possibilities. The most appropriate theory to deal with un- certainties is the theory of fuzzy sets, developed by Zadeh[9] in 1965. But it has an inherent difficulty to set the membership function in each particular cases. Also the theory of intuitionistic fuzzy set is more generalized con- cept than the theory of fuzzy set, but also there have same difficulties. The soft set theory is free from above difficulties. In 2001, P.K.Maji, A.R.Roy, R.Biswas [12, 13] initiated the concept of fuzzy soft sets which is a combi- nation of fuzzy set and soft set. In fact, the notion of fuzzy soft set is more generalized than that of fuzzy set and soft set. Thereafter many researchers have applied this concept on different branches of mathematics, like group theory [1, 6], decision making problems, relations [3, 5], topology [14, 15, 16] etc.. In 1736, Euler first introduced the concept of graph theory. The theory of graph is extremely useful tool for solving combinatorial problems in dif- ferent areas such as geometry, algebra, number theory, topology, operation research, optimization and computer science, etc.. In 1975, Rosenfeld [2] introduced the concept of fuzzy graphs. Thereafter many researchers have 2000 Mathematics Subject Classification. Primary : 03E99, 05C72 ; Secondary : 03E72. Key words and phrases. Soft set, fuzzy soft set, fuzzy graph, fuzzy soft graph. c 2015 Mathematica Moravica 35

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Mathematica MoravicaVol. 19-2 (2015), 35–48

An Introduction to Fuzzy Soft Graph

Sumit Mohinta and T.K. Samanta

Abstract. The notions of fuzzy soft graph, union, intersection of twofuzzy soft graphs are introduced in this paper and a few properties relat-ing to finite union and intersection of fuzzy soft graphs are establishedhere.

1. Introduction

In 1999, D.Molodtsov[4] introduced the notion of soft set theory to solveimprecise problems in economics, engineering and environment. He hasshown several applications of this theory in solving many practical prob-lems. There are many theories like theory of probability, theory of fuzzysets, theory of intuitionistic fuzzy sets, theory of rough sets, etc. which canbe considered as mathematical tools to deal with uncertainties. But all thesetheories have their own inherent difficulties. The theory of probabilities candeal only with possibilities. The most appropriate theory to deal with un-certainties is the theory of fuzzy sets, developed by Zadeh[9] in 1965. But ithas an inherent difficulty to set the membership function in each particularcases. Also the theory of intuitionistic fuzzy set is more generalized con-cept than the theory of fuzzy set, but also there have same difficulties. Thesoft set theory is free from above difficulties. In 2001, P.K.Maji, A.R.Roy,R.Biswas [12, 13] initiated the concept of fuzzy soft sets which is a combi-nation of fuzzy set and soft set. In fact, the notion of fuzzy soft set is moregeneralized than that of fuzzy set and soft set. Thereafter many researchershave applied this concept on different branches of mathematics, like grouptheory [1, 6], decision making problems, relations [3, 5], topology [14, 15, 16]etc..In 1736, Euler first introduced the concept of graph theory. The theoryof graph is extremely useful tool for solving combinatorial problems in dif-ferent areas such as geometry, algebra, number theory, topology, operationresearch, optimization and computer science, etc.. In 1975, Rosenfeld [2]introduced the concept of fuzzy graphs. Thereafter many researchers have

2000 Mathematics Subject Classification. Primary : 03E99, 05C72 ; Secondary : 03E72.Key words and phrases. Soft set, fuzzy soft set, fuzzy graph, fuzzy soft graph.

c©2015 Mathematica Moravica35

36 An Introduction to Fuzzy Soft Graph

generalized the different notions of graph theory using the notions of fuzzysets [7, 8, 10, 17].

In this paper, our aim is to introduce the notion of fuzzy soft graph andthen a few operations, like union, intersections of two fuzzy soft graphs. Alsoit is seen that the collection of fuzzy soft graphs is closed under finite unionand intersection.

2. Preliminaries

Definition 2.1 ([2]). Let V be a nonempty finite set and σ : V → [0, 1].Again, let µ : V × V → [0, 1] such that

µ(x, y) ≤ σ(x) ∧ σ(y) ∀ (x, y) ∈ V × V.Then the pair G := (σ, µ) is called a fuzzy graph over the set V . Here σand µ are respectively called fuzzy vertex and fuzzy edge of the fuzzy graph(σ, µ).A fuzzy graph G := (σ, µ) over the set V is called strong fuzzy graph if

µ(x, y) = σ(x) ∧ σ(y) ∀ (x, y) ∈ V × V.Definition 2.2 ([2]). Let H := (ρ, ν) and G := (σ, µ) be two fuzzy graphsover the set V . Then H is called the fuzzy subgraph of the fuzzy graphG if

ρ(x) ≤ σ(x) and ν(x, y) ≤ µ(x, y) ∀ x, y ∈ V.Definition 2.3 ([11]). Let G1 := (σ1, µ1) and G2 := (σ2, µ2) be two fuzzygraphs over the set V . Then the union of G1 and G2 is another fuzzy graphG3 := (σ3, µ3) over the set V , where

σ3 = σ1 ∨ σ2 and µ3 = µ1 ∨ µ2,i.e. σ3(x) = max{σ1(x), σ2(x)} ∀ x ∈ V

and µ3(x, y) = max{µ1(x, y), µ2(x, y)} ∀ x, y ∈ V.Definition 2.4 ([11]). Let G1 := (σ1, µ1) and G2 := (σ2, µ2) be two fuzzygraphs over the set V . Then the intersection of G1 and G2 is another fuzzygraph G3 := (σ3, µ3) over the set V , where

σ3 = σ1 ∧ σ2 and µ3 = µ1 ∧ µ2,i.e. σ3(x) = min{σ1(x), σ2(x)} ∀ x ∈ V

and µ3(x, y) = min{µ1(x, y), µ2(x, y)} ∀ x, y ∈ V.Let U be an initial universal set and E be a set of parameters. Let IU

denotes the collection of all fuzzy subsets of U and A ⊆ E.

Definition 2.5 ([15]). Let A ⊆ E. Then the mapping FA : E → IU , definedby FA(e) = µeFA

(a fuzzy subset of U), is called fuzzy soft set over (U,E),where µeFA

= 0 if e ∈ E \ A and µeFA6= 0 if e ∈ A and 0 denotes the null

fuzzy set.The set of all fuzzy soft sets over (U,E) is denoted by FS(U,E).

Sumit Mohinta and T.K. Samanta 37

Definition 2.6 ([15]). The fuzzy soft set Fφ ∈ FS(U,E) is called nullfuzzy soft set and it is denoted by Φ. Here Fφ(e) = 0 for every e ∈ E.

Definition 2.7 ([15]). Let FE ∈ FS(U,E) and FE(e) = 1 for all e ∈ E.Then FE is called absolute fuzzy soft set. It is denoted by E.

Definition 2.8 ([15]). Let FA, GB ∈ FS(U,E) and A ⊆ B. If FA(e) ⊆GB(e) for all e ∈ A, i.e., if µeFA

⊆ µeGBfor all e ∈ A, i.e., if µeFA

(x) ≤ µeGB(x)

for all x ∈ U and for all e ∈ A, then FA is said to be fuzzy soft subset ofGB, denoted by FA v GB.

Definition 2.9 ([15]). Let FA, GB ∈ FS(U,E). Then the union of FA andGB is another fuzzy soft set HC defined by HC(e) = µeHC

= µeFA∪ µeGB

forall e ∈ C, where C = A ∪B. Here we write HC = FA tGB.

Definition 2.10 ([15]). Let FA, GB ∈ FS(U,E). Then the intersection ofFA and GB is another a fuzzy soft set HC , defined by HC(e) = µeHC

=µeFA∩ µeGB

for all e ∈ C, where C = A ∩B. Here we write HC = FA uGB.

3. Fuzzy Soft Graph

Definition 3.1. Let V = {x1, x2, · · · , xn}(non-empty set), E(parametersset) and A ⊆ E. Also let(i) ρ : A −→ F (V )(Collection of all fuzzy subsets in V )

e 7→ ρ(e) = ρe(say)and ρe : V −→ [0, 1]

xi 7→ ρe(xi)(A, ρ) : Fuzzy soft vertex.(ii)µ : A −→ F (V × V )(Collection of all fuzzy subsets in V × V )

e 7→ µ(e) = µe(say)and µe : V × V −→ [0, 1]

(xi, xj) 7→ µe(xi, xj)(A,µ) : Fuzzy soft edge.

Then ((A, ρ), (A,µ)) is called fuzzy soft graph if and only if µe(xi, xj)≤ ρe(xi) ∧ ρe(xj) ∀e ∈ A and ∀i, j = 1, 2, · · · , n and this fuzzy soft graph isdenoted by GA,V .

Example 3.1. Consider a fuzzy soft graph GE,V , where V = {x1, x2, x3}and E = {e1, e2, e3}. Here GE,V is described by Table 1 and µe(xi, xj) = 0for all (xi, xj) ∈ V × V \ {(x1, x2), (x1, x3), (x2, x3)} and for all e ∈ E.

Definition 3.2. The fuzzy soft graph HA,V = ((A, ζ), (A, ν)) is called afuzzy soft subgraph of GA,V = ((A, ρ), (A,µ)) if ρe(xi) ≥ ζe(xi) for allxi ∈ V, e ∈ A and νe(xi, xj) ≤ µe(xi, xj) for all xi, xj ∈ V, e ∈ A.

Example 3.2. Consider V = {x1, x2, x3} and E = {e1, e2, e3}. Here, afuzzy soft graph HA,V is given by Table 2 and νe(xi, xj) = 0 for all (xi, xj) ∈

38 An Introduction to Fuzzy Soft Graph

Table 1

ρ x1 x2 x3e1 .5 .2 0

e2 .4 .7 .6

e3 .5 .9 .3

µ (x1, x2) (x1, x3) (x2, x3)

e1 .2 0 0

e2 .4 .4 .6

e3 .2 .1 .3

Figure 1. Fuzzy Soft Graph.

V × V \ {(x1, x2), (x1, x3), (x2, x3)} and for all e ∈ E. HA,V is a fuzzy softsubgraph of GA,V , where GA,V given in the Example (3.1).

Table 2

ζ x1 x2 x3e1 .3 .1 0

e2 0 .4 .3

e3 .5 0 .2

ν (x1, x2) (x1, x3) (x2, x3)

e1 .1 0 0

e2 0 0 .3

e3 0 .1 0

Definition 3.3. The fuzzy soft subgraph HA,V = ((A, ζ), (A, ν)) is said tobe spanning fuzzy soft subgraph of GA,V = ((A, ρ), (A,µ)) if ρe(xi) =ζe(xi) for all xi ∈ V, e ∈ A.In this case, the two fuzzy soft graphs have same fuzzy soft vertex set, theydiffer only in the arc weights.

Example 3.3. Consider V = {x1, x2, x3} and E = {e1, e2, e3}. Here, afuzzy soft graph HA,V is given by Table 3 and νe(xi, xj) = 0 for all (xi, xj) ∈V × V \ {(x1, x2), (x1, x3), (x2, x3)} and for all e ∈ E. HA,V is a spanningfuzzy soft subgraph of GA,V , where GA,V given in the Example (3.1).

Sumit Mohinta and T.K. Samanta 39

Figure 2. Fuzzy Soft Subgraph.

Table 3

ζ x1 x2 x3e1 .5 .2 0

e2 .4 .7 .6

e3 .5 .9 .3

ν (x1, x2) (x1, x3) (x2, x3)

e1 .1 0 0

e2 .3 .2 .5

e3 .1 .1 .2

Figure 3. Spanning Fuzzy Soft subgraph.

Definition 3.4. The underlying crisp graph of a fuzzy soft graph GA,V= ((A, ρ), (A,µ)) is denoted by G∗ = (ρ∗, µ∗) where

ρ∗ = {xi ∈ V : ρe(xi) > 0 for some e ∈ E},µ∗ = {(xi, xj) ∈ V × V : µe(xi, xj) > 0 for some e ∈ E}.

Definition 3.5. A fuzzy soft graph GA,V = ((A, ρ), (A,µ)) is called strongfuzzy soft graph if µe(xi, xj) = ρe(xi) ∧ ρe(xj) for all (xi, xj) ∈ µ∗, e ∈ A

40 An Introduction to Fuzzy Soft Graph

and is a complete fuzzy soft graph if µe(xi, xj)= ρe(xi) ∧ ρe(xj) for all xi, xj ∈ ρ∗, e ∈ A.

Example 3.4. For example of strong fuzzy soft graph, consider V = {x1, x2, x3}and E = {e1, e2, e3}. GA,V is given by Table 4 and µe(xi, xj) = 0 for all(xi, xj) ∈ V × V \ {(x1, x2), (x1, x3),(x2, x3)} and for all e ∈ E. Here, GA,V is a strong fuzzy soft graph.

Table 4

ρ x1 x2 x3e1 .5 .2 0

e2 .4 .7 .6

e3 .5 .9 .3

µ (x1, x2) (x1, x3) (x2, x3)

e1 .2 0 0

e2 .4 .4 .6

e3 .5 .3 .3

Figure 4. Strong Fuzzy Soft graph.

Example 3.5. For example of complete fuzzy soft graph, consider V ={x1, x2, x3} and E = {e1, e2, e3}. GA,V is given by Table 5 and µe(xi, xj) = 0for all (xi, xj) ∈ V × V \ {(x1, x1), (x1, x3),(x3, x3)} and for all e ∈ E. Here, GA,V is a complete fuzzy soft graph.

Table 5

ρ x1 x2 x3e1 .2 0 .6

e2 .5 0 0

e3 .0 0 .8

µ (x1, x1) (x1, x3) (x3, x3)

e1 .2 .2 .6

e2 .5 0 0

e3 0 0 .8

Sumit Mohinta and T.K. Samanta 41

Figure 5. Complete Fuzzy Soft graph.

Definition 3.6. Let V1, V2 ⊂ V and A,B ⊂ E. Then the union of twofuzzy soft graphs G1

A,V1= ((A, ρ1e), (A,µ

1e)) and G2

B,V2= ((B, ρ2e), (B,µ

2e)) is

defined to be G3C,V3

= ((C, ρ3e), (C, µ3e)) (say), where C = A∪B, V3 = V1∪V2

andρ3e(xi) = ρ1e(xi) for all e ∈ A \B and xi ∈ V1 \ V2,

= 0 for all e ∈ A \B and xi ∈ V2 \ V1,

= ρ1e(xi) for all e ∈ A \B and xi ∈ V1 ∩ V2,

= ρ2e(xi) for all e ∈ B \A and xi ∈ V2 \ V1,

= 0 for all e ∈ B \A and xi ∈ V1 \ V2,

= ρ2e(xi) for all e ∈ B \A and xi ∈ V1 ∩ V2,

= ρ1e(xi) ∨ ρ2e(xi) for all e ∈ A ∩B and xi ∈ V1 ∩ V2,

= ρ1e(xi) for all e ∈ A ∩B and xi ∈ V1 \ V2,

= ρ2e(xi) for all e ∈ A ∩B and xi ∈ V2 \ V1,andµ3e(xi, xj) = µ1e(xi, xj) if e ∈ A \B and (xi, xj) ∈

(V1 × V1) \ (V2 × V2),

= 0 if e ∈ A \B and (xi, xj) ∈ (V2 × V2) \ (V1 × V1),

= µ1e(xi, xj) if e ∈ A \B and (xi, xj) ∈(V1 × V1) ∩ (V2 × V2),

= µ2e(xi, xj) if e ∈ B \A and (xi, xj) ∈(V2 × V2) \ (V1 × V1),

42 An Introduction to Fuzzy Soft Graph

= 0 if e ∈ B \A and (xi, xj) ∈ (V1 × V1) \ (V2 × V2),

= µ2e(xi, xj) if e ∈ B \A and (xi, xj) ∈(V1 × V1) ∩ (V2 × V2),

= µ1e(xi, xj) ∨ µ2e(xi, xj) if e ∈ A ∩B and(xi, xj) ∈ (V1 × V1) ∩ (V2 × V2),

= µ1e(xi, xj) if e ∈ A ∩B and(xi, xj) ∈ (V1 × V1) \ (V2 × V2),

= µ2e(xi, xj) if e ∈ A ∩B and(xi, xj) ∈ (V2 × V2) \ (V1 × V1).

Example 3.6. Consider V = {x1, x2, x3, x4, x5, x6} and E ={e1, e2, e3, e4}. Let V1 = {x1, x2, x3, x4} , A = {e1, e2,e3} and V2 = {x1, x2, x5, x6}, B = {e2, e3, e4}.G1A,V1

is defined by Table 6 and µ1e(xi, xj) = 0 for all (xi, xj)

∈ V1 × V1 \ {(x1, x2), (x2, x3), (x3, x4)} and for all e ∈ A.G2B,V2

is defined by Table 7 and µ2e(xi, xj) = 0 for all (xi, xj)

∈ V2 × V2 \ {(x1, x2), (x2, x5), (x5, x6)} and for all e ∈ B.Then the union of G1

A,V1and G2

B,V2is G3

C,V3given by the Table 8 and

µ3e(xi, xj) = 0 for all (xi, xj) ∈ V3 × V3 \ {(x1, x2), (x2, x3),(x3, x4), (x2, x5), (x5, x6)} and for all e ∈ C.

Table 6

ρ1 x1 x2 x3 x4e1 .1 .5 .8 .2

e2 .8 .2 .3 .9

e3 .3 .8 .7 0

µ1 (x1, x2) (x2, x3) (x3, x4)

e1 .1 .4 .1

e2 .2 .3 .2

e3 .2 .5 0

Table 7

ρ2 x1 x2 x5 x6e2 .2 .3 .9 .7

e3 .6 .4 .5 0

e4 0 .7 .5 .4

µ2 (x1, x2) (x2, x5) (x5, x6)

e2 .2 .2 .5

e3 .4 .3 0

e4 0 .2 .3

Proposition 3.1. Let G3C be the union of the fuzzy soft graphs G1

A and G2B.

Then G3C = G1

A ∪G2B is a fuzzy soft graph.

Sumit Mohinta and T.K. Samanta 43

Table 8

ρ3 x1 x2 x3 x4 x5 x6e1 .1 .5 .8 .2 0 0

e2 .8 .3 .3 .9 .9 .7

e3 .6 .8 .7 0 .5 0

e4 0 .7 0 0 .5 .4

µ3 (x1, x2) (x2, x3) (x3, x4) (x2, x5) (x5, x6)

e1 .1 .4 .1 0 0

e2 .2 .3 .2 .2 .5

e3 .4 .5 0 .3 0

e4 0 0 0 .2 .3

Figure 6. Fuzzy Soft graph 6.

Figure 7. Fuzzy Soft graph 7.

44 An Introduction to Fuzzy Soft Graph

Figure 8. Union of the Fuzzy Soft graphs 6 & 7.

Proof. Suppose that e ∈ A \B and (xi, xj) ∈ (V1×V1) \ (V2×V2). Then bythe Definition (3.6), we have

µ3e(xi, xj) = µ1e(xi, xj)

≤ min{ρ1e(xi), ρ1e(xj)} = min{ρ3e(xi), ρ3e(xj)}.Now, if e ∈ A \B and (xi, xj) ∈ (V2 × V2) \ (V1 × V1) then obviously,

µ3e(xi, xj) = 0 ≤ min{ρ3e(xi), ρ3e(xj)}.Again, if e ∈ A \B and (xi, xj) ∈ (V1 × V1) ∩ (V2 × V2). Then

µ3e(xi, xj) = µ1e(xi, xj)

≤ min{ρ1e(xi), ρ1e(xj)} = min{ρ3e(xi), ρ3e(xj)}.Similarly, if e ∈ B \A, in all cases we have

µ3e(xi, xj) ≤ min{ρ3e(xi), ρ3e(xj)}.Now, suppose e ∈ A ∩B and (xi, xj) ∈ (V1 × V1) ∩ (V2 × V2). Then

µ3e(xi, xj) = max{µ1e(xi, xj), µ2e(xi, xj)}

≤ max{min{ρ1e(xi), ρ1e(xj)},min{ρ2e(xi), ρ2e(xj)}}≤ max{min{ρ1e(xi), ρ2e(xi)},min{ρ1e(xj), ρ2e(xj)}}≤ min{max{ρ1e(xi), ρ2e(xi)},max{ρ1e(xj), ρ2e(xj)}}

= min{ρ3e(xi), ρ3e(xj)}.As in the previous, if e ∈ A ∩ B and (xi, xj) ∈ (V1 × V1) \ (V2 × V2) or(xi, xj) ∈ (V2 × V2) \ (V1 × V1), it can be shown that

µ3e(xi, xj) ≤ min{ρ3e(xi), ρ3e(xj)}.

Hence, G3C = G1

A ∪G2B is a fuzzy soft graph. �

Proposition 3.2. If G3C is the union of two fuzzy soft graphs G1

A and G2B,

then both G1A and G2

B are fuzzy soft subgraphs of G3C .

Sumit Mohinta and T.K. Samanta 45

Definition 3.7. Let V1, V2 ⊂ V and A,B ⊂ E. The intersection of twofuzzy soft graphs G1

A,V1= ((A, ρ1e), (A,µ

1e)) and G2

B,V2= ((B, ρ2e), (B,µ

2e))

is G3C,V3

= ((C, ρ3e), (C, µ3e)) (say), where C = A ∩B and V3 = V1 ∩ V2 and

ρ3e(xi) = ρ1e(xi) ∧ ρ2e(xi) for all xi ∈ V3 and e ∈ C, and µ3e(xi, xj) =µ1e(xi, xj) ∧ µ2e(xi, xj) if xi, xj ∈ V3 and e ∈ C.

Example 3.7. Consider V = {x1, x2, x3, x4} and E = {e1, e2, e3}. LetV1 = {x1, x2, x3}, V2 = {x2, x3, x4} , A = {e1, e2}, B = {e2, e3}.G1A,V1

is defined by Table 9 and µ1e(xi, xj) = 0 for all (xi, xj) ∈ V1 × V1 \{(x1, x2), (x1, x3), (x2, x3)} and for all e ∈ A.G2B,V2

is defined by Table 10 and µ2e(xi, xj) = 0 for all (xi, xj) ∈ V2 × V2 \{(x2, x3), (x2, x4), (x3, x4)} and for all e ∈ B.So, V3 = {x2, x3} and C = {e2}.Then the intersection of G1

A,V1and G2

B,V2is G3

C,V3given by the Table 11 and

µ3e(xi, xj) = 0 for all (xi, xj) ∈ V3 × V3 \ {(x2, x2), (x3, x3), (x3, x2)} and forall e ∈ C.

Table 9

ρ1 x1 x2 x3e1 .2 .4 .6

e2 .3 .9 .6

µ1 (x1, x2) (x1, x3) (x2, x3)

e1 .2 .1 .3

e2 .1 .2 .5

Figure 9. Fuzzy Soft graph 9.

Table 10

ρ2 x2 x3 x4e2 .3 .5 .4

e3 .1 .4 .7

µ2 (x2, x3) (x2, x4) (x3, x4)

e2 .2 .3 .3

e3 .05 .1 .2

46 An Introduction to Fuzzy Soft Graph

Figure 10. Fuzzy Soft graph 10.

Table 11

ρ3 x2 x3e2 .3 .5

µ3 (x2, x3)

e2 .2

Figure 11. Intersection of the Fuzzy Soft graphs 9 & 10.

Proposition 3.3. Let G3C be the intersection of the fuzzy soft graphs

G1A and G2

B. Then G3C = G1

A ∩G2B is a fuzzy soft graph.

Proof. Let xi, xj ∈ V3 and e ∈ C. Then we have

µ3e(xi, xj) = min{µ1e(xi, xj), µ2e(xi, xj)}≤ min{min{ρ1e(xi), ρ1e(xj)},min{ρ2e(xi), ρ2e(xj)}}= min{min{ρ1e(xi), ρ2e(xi)},min{ρ1e(xj), ρ2e(xj)}}= min{ρ3e(xi), ρ2e(xj)}.

This proves the proposition. �

Proposition 3.4. If G3C is the intersection of two fuzzy soft graphs

G1A and G2

B, then G3C is fuzzy soft subgraph of both G1

A and G2B.

4. Conclusion

In the definition (3.7), if we replace the set C = A∪B and V3 = V1 ∪ V2,the intersection of two fuzzy soft graphs can be defined as in the same way

Sumit Mohinta and T.K. Samanta 47

of the definition (3.6) and this intersection could be termed as generalizedintersection of two fuzzy soft graphs. In fact, with respect to generalizedintersection, propositions (3.3) and (3.4) can be easily verified.

Acknowledgment. The authors are grateful to the reviewers for theirvaluable suggestions to improve the quality of this paper.

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48 An Introduction to Fuzzy Soft Graph

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Sumit MohintaDepartment of MathematicsSudhir Memorial InstituteKolkata, 700132West BengalIndiaE-mail address: [email protected]

T.K. SamantaDepartment of MathematicsUluberia College, UluberiaHowrah, 711315 West BengalIndiaE-mail address: [email protected]