Neutrosophic Sets and Systems, Vol. 35, 2020 University of New Mexico Basic operations on hypersoft sets and hypersoft point Mujahid Abbas 1, Ghulam Murtaza 2,* and Florentin Smarandache 3 1 Department of Mathematics, Government College University, Lahore 54000, Pakistan and Department of Mathematics and Applied Mathematics,, University of Pretoria, Lynnwood Road, Pretoria 0002, South Africa; [email protected], 2Department of Mathematics, University of Management Technology, Lahore, 54000, Pakistan; [email protected] 2 University of New Mexico, USA; [email protected]; [email protected] * Correspondence: [email protected] Abstract: The aim of this paper is to initiat formal study of hypersoft sets. We first, present basic operations like union, intersection and difference of hypersoft sets; basic ingrediants for topological structures on the collection of hypersoft sets. Moreover we introduce hypersoft points in different envorinments like fuzzy hypersoft set, intuitionistic fuzzy hypersoft set, neutrosophic hypersoft, plithogenic hypersoft set, and give some basic properties of hypersoft points in these envorinments. We expect that this will constitue an appropriate framework of hypersoft functions and the study of hypersoft function spaces. Examples are provided to explain the newly defined concepts. Keywords: soft set; hypersoft set; set operations on hypersoft sets; hypersoft point; fuzzy hypersoft set; intuitionistic fuzzy hypersoft set; neutrosophic hypersoft; plithogenic hypersoft set. 1. Introduction Molodtsov [16] defined soft set as a mathematical tool to deal with uncertainties associated with real world problems. Soft set theory has application in decision making, demand analysis, forecasting, information sciences and other disciplines (see for example, [ 13, 14, 15, 17, 18, 19, 20, 21, 22, 23]). Plithogenic and neutrosophic hypersoft sets theory is being applied successfully in decision making problems (see, [2, 3, 4, 5, 6, 7, 8, 9,10,11,12]). By definition, a soft set can be identified by a pair (πΉ,π΄), where πΉ stands for a multivalued function defined on the set of parameters π΄. Smarandache [1] extended the notion of a soft set to the hypersoft set by replacing the function πΉ with a multi-argument function defined on the Cartesian product of π different set of parameters. This concept is more flexible than soft set and more suitable in the context of decision making problems. We expect the notion of hypersoft set will attract the attention of researchers working on soft set theory and its diverse applications. The purpose of this paper is to initiate a formal investigation in this new area of research. As a first step, we present the basic operations like union, intersection and difference of hypersoft sets. Moreover we introduce hypersoft points and some basic properties of these points Mujahid Abbas, Ghulam Murtaza, and Florentin Smarandache, Basic operations on hypersoft sets and hypersoft point Neutrosophic Sets and Systems, Vol. 35, 2020 408 which may provide the foundation for the hypersoft functions and hence the hypersoft fixed point theory. 2. Operations on hypersoft sets In this section, we define basic operations on hypersoft sets. Smarandache defined the hypersoft set in the following manner: Definition 1 [1] Let π be a universe of discourse, π(π) the power set π and πΈ ,πΈ ,β¦,πΈ the pairwise 1 2 π disjoint sets of parameters. Let π΄ be the nonempty subset of πΈ for each π =1,2,...,π. A hypersoft set can be π π identified by the pair (πΉ,π΄ Γπ΄ Γβ―Γπ΄ ), where: 1 2 π πΉ:π΄ Γπ΄ Γβ―Γπ΄ βπ(π). 1 2 π For sake of simplicity, we write the symbols π for πΈ ΓπΈ Γβ―ΓπΈ , π for π΄ Γπ΄ Γβ―Γπ΄ and 1 2 π 1 2 π π for an element of the set π. We also suppose that none of the set π΄ is empty. π Definition 2 [1] A hypersoft set; on a crisp universe of discourse π is called Crisp Hypersoft set (or simply "hypersoft set"); πΆ on a fuzzy universe of discourse π is called Fuzzy Hypersoft set. πΉ on a Intuitionistic Fuzzy universe of discourse π is called Intuitionistic Fuzzy Hypersoft set; πΌπΉ on a Neutrosophic universe of discourse π is called Neutrosophic Hypersoft Set; π on a Plithogenic universe of discourse π is called Plithogenic Hypersoft Set. π The nature of πΉ(π) is determined by the nature of universe of discourse. Therefore π(π) depends upon the nature of universe. We denote β(π ,π) by the family of all *-hypersoft sets over β (π ,π), where β can take any value in the set {πΆ,πΉ,πΌπΉ,π,π}, where symbols πΆ,πΉ,πΌπΉ,π,π denote β Crisp, Fuzzy, Intuitionistic Fuzzy, Neutrosophic, and Plithogenic sets, respectively. The following are the basic operations on *-hypersoft set. Definition 3 Let π be a universe of discourse and π¨ a subset of π¬. Then (πΉ,π¨) is called β 1. a null *-hypersoft set if for each parameter πΆβπ¨, πΉ(πΆ) is an 0 . We will denote it by π· . β π¨ 2. an absolute *-hypersoft set if for each parameter πΆβπ¨, πΉ(πΆ)=π . We will denote it by πΜ . β π¨ π₯ π₯ Remark 1 We consider 0 =β for empty set, 0 ={ ,π₯ βπ } for null fuzzy set, 0 ={ ,π₯ βπ } πΆ πΉ 0 πΉ πΌπΉ <0,1> πΌπΉ π₯ for null intuitionistic fuzzy set, 0 ={ ,π₯ βπ } for null neutrosophic set. However, in case of π <0,1,1> π plithogenic set, we have the following notations: β’ Null plithgenic crisp set 0 ={π₯(0,0,...,0),forallπ₯ βπ }. ππΆ π β’ Universal plithgenic crisp set 1 ={π₯(1,1,...,1),forallπ₯ βπ }. ππΆ π Note that null plithgenic fuzzy set will be same as null plithgenic crisp set and universal plithgenic fuzzy set will be the same as universal plithgenic crisp set. Mujahid Abbas, Ghulam Murtaza, and Florentin Smarandache, Basic operations on hypersoft sets and hypersoft point Neutrosophic Sets and Systems, Vol. 35, 2020 409 β’ Null plithgenic intuitionistic fuzzy set 0 ={π₯((0,1),(0,1),...,(0,1)),forallπ₯ βπ }. ππΌπΉ π β’ Universal plithgenic intuitionistic fuzzy set 1 ={π₯((1,0),(1,0),...,(1,0)),forallπ₯ βπ }. ππΌπΉ π β’ Null plithgenic neutrosophic set 0 ={π₯((0,1,1),(0,1,1),...,(0,1,1)),forallπ₯ βπ }. ππ π β’ Universal plithgenic neutrosophic set 1 ={π₯((1,0,0),(1,0,0),...,(1,0,0)),forallπ₯ βπ}. ππ Definition 4 Let (πΉ,π¨) and (πΊ,π©) be two *-hypersoft sets over π . Then union of (πΉ,π¨) and (πΊ,π©) is β denoted by (π»,πͺ)=(πΉ,π¨)βͺΜ(πΊ,π©) with πͺ=πΆ ΓπΆ Γβ―ΓπΆ , where πΆ =π΄ βͺπ΅ for π =1,2,...,π, 1 2 π π π π and π» is defined by πΉ(π), ifπβπβπ πΊ(π), ifπβπβπ π»(π)=( πΉ(π)βͺ πΊ(π), ifπβπβ©π, β 0 , else, β where π=(π ,π ,...,π )βπΆ. 1 2 π Remark 2 Note that, in the case of union of two hypersoft sets the set of parameters is a Cartesian product of sets of parameters whereas in the case of union of two soft sets the set of parameter is just the union of sets of parameters. Definition 5 Let (πΉ,π¨) and (πΊ,π©) be two *-hypersoft sets over π . Then intersection of (πΉ,π¨) and (πΊ,π©) β is denoted by (π»,πͺ)=(πΉ,π¨)β©Μ(πΊ,π©), where πͺ=πΆ ΓπΆ Γβ―ΓπΆ is such that πΆ =π΄ β©π΅ for π = 1 2 π π π π 1,2,...,π and π» is defined as π»(π)=πΉ(π)β© πΊ(π), β where πΆ=(π ,π ,...,π )βπͺ. If πΆ is an empty set for some π, then (πΉ,π¨)β©Μ(πΊ,π©) is defined to be a null 1 2 π π *-hypersoft set. Definition 6 Let (πΉ,π¨) and (πΊ,π©) be two *-hypersoft sets over π . Then (πΉ,π¨) is called a *-hypersoft β subset of (πΊ,π©) if π¨βπ©, and πΉ(πΆ)β πΊ(πΆ) for all πΆβπ¨. We denote this by (πΉ,π¨)βΜ (πΊ,π©). Thus (πΉ,π¨) β and (πΊ,π©) are said to equal if (πΉ,π¨)βΜ (πΊ,π©) and (πΉ,π¨)βΜ (πΊ,π©). Definition 7 Let (πΉ,π¨) and (πΊ,π©) be two *-hypersoft sets over π . Then *-hypersoft difference of (πΉ,π¨) β and (πΊ,π©), denoted by (π»,πͺ)=(πΉ,π¨)\Μ(πΊ,π©), where πͺ=πΆ ΓπΆ Γβ―ΓπΆ is such that πΆ =π΄ β©π΅ for 1 2 π π π π π =1,2,...,π, and π» is defined by π»(π)=πΉ(π)\ πΊ(π), β where π=(π ,π ,...,π )βπ. If πΆ is an empty set for some π then (πΉ,π)\Μ(πΊ,π) is defined to be 1 2 π π (πΉ,π). Definition 8 The complement of a *-hypersoft set (πΉ,π¨) is denoted as (πΉ,π¨)π and is defined by (πΉ,π¨)π = (πΉπ,π¨) where πΉπ(πΆ) is the *-complemet of πΉ(πΆ) for each πΆβπ¨. Example 1 Let U={x ,x ,x ,x }. Define the attributes sets by: 1 2 3 4 Mujahid Abbas, Ghulam Murtaza, and Florentin Smarandache, Basic operations on hypersoft sets and hypersoft point Neutrosophic Sets and Systems, Vol. 35, 2020 410 πΈ ={π ,π },πΈ ={π ,π },πΈ ={π ,π }. 1 11 12 2 21 22 3 31 32 Suppose that π΄ ={π ,π },π΄ ={π ,π },π΄ ={π },and 1 11 12 2 21 22 3 31 π΅ ={π },π΅ ={π ,π },π΅ ={π ,π } 1 11 2 21 22 3 31 32 that is,. π΄ ,π΅ βπΈ for each π =1,2,3. π π π Let the crisp hypersoft sets (πΉ,π) and (πΊ,π) be defined by (πΉ,π)={((π ,π ,π ),{π₯ ,π₯ }),((π ,π ,π ),{π₯ }), 11 21 31 1 2 11 22 31 2 ((π ,π ,π ),{π₯ ,π₯ }),((π ,π ,π ),{π₯ ,π₯ })}. 12 21 31 3 4 12 22 31 1 4 and (πΊ,π)={((π ,π ,π ),{π₯ ,π₯ }),((π ,π ,π ),{π₯ }), 11 21 31 2 3 11 22 31 2 ((π ,π ,π ),{π₯ ,π₯ }),((π ,π ,π ),{π₯ ,π₯ })}. 11 21 32 1 4 11 22 32 3 4 We have excluded those πβπ for which πΉ(π) is an empty set (similarly for those πβπ for which πΊ(π) is an empty set). Then the union and intersections of (πΉ,π) and (πΊ,π) are given by: (πΉ,π)βͺΜ(πΊ,π)={((π ,π ,π ),{π₯ ,π₯ ,π₯ }),((π ,π ,π ),{π₯ }), 11 21 31 1 2 3 11 22 31 2 ((π ,π ,π ),{π₯ ,π₯ }),((π ,π ,π ),{π₯ ,π₯ }), 12 21 31 3 4 12 22 31 1 4 ((π ,π ,π ),{π₯ ,π₯ }),((π ,π ,π ),{π₯ ,π₯ }), 11 21 32 1 4 11 22 32 3 4 ((π ,π ,π ),0 ),((π ,π ,π ),0 )}; 12 21 32 πΆ 12 22 32 πΆ and (πΉ,π)β©Μ(πΊ,π)={((π ,π ,π ),{π₯ }),((π ,π ,π ),{π₯ })}. 11 21 31 2 11 22 31 2 The differences (πΉ,π)\Μ(πΊ,π) and (πΊ,π)\Μ(πΉ,π) are the following (πΉ,π)\Μ(πΊ,π)={((π ,π ,π ),{π₯ }),((π ,π ,π ),0 )}; 11 21 31 1 11 22 31 πΆ (πΊ,π)\Μ(πΉ,π)={((π ,π ,π ),{π₯ }),((π ,π ,π ),0 )}. 11 21 31 3 11 22 31 πΆ Example 2 Let U={x ,x ,x ,x }. Define the attributes sets by: 1 2 3 4 πΈ ={π ,π },πΈ ={π ,π },πΈ ={π ,π }. 1 11 12 2 21 22 3 31 32 Suppose that π΄ ={π ,π },π΄ ={π ,π },π΄ ={π },and 1 11 12 2 21 22 3 31 π΅ ={π },π΅ ={π ,π },π΅ ={π ,π } 1 11 2 21 22 3 31 32 are subsets of πΈ for each π =1,2,3, that is,. π΄ ,π΅ βπΈ for each π. π π π π Let the fuzzy hypersoft sets (πΉ,π) and (πΊ,π) be defined by (πΉ,π)={((π ,π ,π ),{π₯1,π₯2}),((π ,π ,π ),{π₯2}), 11 21 31 0.5 0.7 11 22 31 0.3 ((π ,π ,π ),{π₯3,π₯4}),((π ,π ,π ),{π₯1,π₯4})}. 12 21 31 0.8 0.9 12 22 31 0.5 0.4 and (πΊ,π)={((π ,π ,π ),{π₯2,π₯3}),((π ,π ,π ),{π₯2}), 11 21 31 0.2 0.9 11 22 31 0.6 ((π ,π ,π ),{π₯1,π₯4}),((π ,π ,π ),{π₯3,π₯4})}. 11 21 32 0.4 0.7 11 22 32 0.2 0.8 We have excluded those πβπ for which πΉ(π) is a null fuzzy set (similarly for those πβπ for which πΊ(π) is a null fuzzy set). Then the union and intersections of (πΉ,π) and (πΊ,π) are given by: Mujahid Abbas, Ghulam Murtaza, and Florentin Smarandache, Basic operations on hypersoft sets and hypersoft point Neutrosophic Sets and Systems, Vol. 35, 2020 411 (πΉ,π)βͺΜ(πΊ,π)={((π ,π ,π ),{π₯1,π₯2,π₯3}),((π ,π ,π ),{π₯2}), 11 21 31 0.5 0.7 0.9 11 22 31 0.6 ((π ,π ,π ),{π₯3,π₯4}),((π ,π ,π ),{π₯1,π₯4}), 12 21 31 0.8 0.9 12 22 31 0.5 0.4 ((π ,π ,π ),{π₯1,π₯4}),((π ,π ,π ),{π₯3,π₯4}), 11 21 32 0.4 0.7 11 22 32 0.2 0.8 ((π ,π ,π ),0 ),((π ,π ,π ),0 )}; 12 21 32 πΉ 12 22 32 πΉ and (πΉ,π)β©Μ(πΊ,π)={((π ,π ,π ),{π₯2}),((π ,π ,π ),{π₯2})}. 11 21 31 0.2 11 22 31 0.3 The differences (πΉ,π)\Μ(πΊ,π) and (πΊ,π)\Μ(πΉ,π) are the following (πΉ,π)\Μ(πΊ,π)={((π ,π ,π ),{π₯1,π₯2}),((π ,π ,π ),0 )}; 11 21 31 0.5 0.5 11 22 31 πΉ (πΊ,π)\Μ(πΉ,π)={((π ,π ,π ),{π₯3}),((π ,π ,π ),{π₯2})}. 11 21 31 0.9 11 22 31 0.3 Example 3 Let U={x ,x ,x ,x }. Define the attributes sets by: 1 2 3 4 πΈ ={π ,π },πΈ ={π ,π },πΈ ={π ,π }. 1 11 12 2 21 22 3 31 32 Suppose that π΄ ={π ,π },π΄ ={π ,π },π΄ ={π },and 1 11 12 2 21 22 3 31 π΅ ={π },π΅ ={π ,π },π΅ ={π ,π } 1 11 2 21 22 3 31 32 that is,. π΄ ,π΅ βπΈ for each π =1,2,3. π π π Let the intuitionistic fuzzy hypersoft sets (πΉ,π) and (πΊ,π) be defined by (πΉ,π)={((π ,π ,π ),{ π₯1 , π₯2 }),((π ,π ,π ),{ π₯2 }), 11 21 31 11 22 31 <0.5,0.3> <0.7,0.2> <0.3,0.5> ((π ,π ,π ),{ π₯3 , π₯4 }),((π ,π ,π ),{ π₯1 , π₯4 })}. 12 21 31 <0.8,0.1> <0.1,0.5> 12 22 31 <0.5,0.3> <0.4,0.2> and (πΊ,π)={((π ,π ,π ),{ π₯2 , π₯3 }),((π ,π ,π ),{ π₯2 }), 11 21 31 <0.2,0.6> <0.8,0.1> 11 22 31 <0.6,0.3> ((π ,π ,π ),{ π₯1 , π₯4 }),((π ,π ,π ),{ π₯3 , π₯4 })}. 11 21 32 <0.4,0.5> <0.7,0.2> 11 22 32 <0.4,0.2> <0.1,0.8> We have excluded all those πβπ for which πΉ(π) is a null intuitionistic fuzzy set (similarly for those πβπ for which πΊ(π) is a null intuitionistic fuzzy set). The union and intersections of (πΉ,π) and (πΊ,π) are given by: (πΉ,π)βͺΜ(πΊ,π) ={((π ,π ,π ),{ π₯1 , π₯2 , π₯3 }),((π ,π ,π ),{ π₯2 }), 11 21 31 <0.5,0.3> <0.7,0.2> <0.8,0.1> 11 22 31 <0.6,0.3> ((π ,π ,π ),{ π₯3 , π₯4 }),((π ,π ,π ),{ π₯1 , π₯4 }), 12 21 31 <0.8,0.1> <0.1,0.5> 12 22 31 <0.5,0.3> <0.4,0.2> ((π ,π ,π ),{ π₯1 , π₯4 }),((π ,π ,π ),{ π₯3 , π₯4 }), 11 21 32 <0.4,0.5> <0.7,0.2> 11 22 32 <0.4,0.2> <0.1,0.8> ((π ,π ,π ),0 ),((π ,π ,π ),0 )}; 12 21 32 πΌπΉ 12 22 32 πΌπΉ and (πΉ,π)β©Μ(πΊ,π)={((π ,π ,π ),{ π₯2 }),((π ,π ,π ),{ π₯2 })}. 11 21 31 <0.2,0.6> 11 22 31 <0.3,0.5> Mujahid Abbas, Ghulam Murtaza, and Florentin Smarandache, Basic operations on hypersoft sets and hypersoft point Neutrosophic Sets and Systems, Vol. 35, 2020 412 The differences (πΉ,π)\Μ(πΊ,π) and (πΊ,π)\Μ(πΉ,π) are the following (πΉ,π)\Μ(πΊ,π)={((π ,π ,π ),{ π₯1 , π₯2 }),((π ,π ,π ),{ π₯2 })}; 11 21 31 <0.5,0.3> <0.6,0.2> 11 22 31 <0.3,0.6> (πΊ,π)\Μ(πΉ,π)={((π ,π ,π ),{ π₯2 , π₯3 }),((π ,π ,π ),{ π₯2 })}. 11 21 31 <0.2,0.7> <0.8,0.1> 11 22 31 <0.5,0.3> Example 4 Let U={x ,x ,x ,x }. Define the attributes sets by: 1 2 3 4 πΈ ={π ,π },πΈ ={π ,π },πΈ ={π ,π }. 1 11 12 2 21 22 3 31 32 Suppose that π΄ ={π ,π },π΄ ={π ,π },π΄ ={π },and 1 11 12 2 21 22 3 31 π΅ ={π },π΅ ={π ,π },π΅ ={π ,π } 1 11 2 21 22 3 31 32 that is,. π΄ ,π΅ βπΈ for each π =1,2,3. π π π Let the neutrosophic hypersoft sets (πΉ,π) and (πΊ,π) be defined by (πΉ,π)={((π ,π ,π ),{ π₯1 , π₯2 }),((π ,π ,π ),{ π₯2 }), 11 21 31 <0.5,0.2,0.3> <0.7,0.3,0.2> 11 22 31 <0.3,0.2,0.5> ((π ,π ,π ),{ π₯3 , π₯4 }),((π ,π ,π ),{ π₯1 , π₯4 })}. 12 21 31 <0.8,0.4,0.1> <0.1,0.5,0.5> 12 22 31 <0.5,0.2,0.3> <0.4,0.3,0.2> and (πΊ,π)={((π ,π ,π ),{ π₯2 , π₯3 }),((π ,π ,π ),{ π₯2 }), 11 21 31 <0.2,0.5,0.6> <0.8,0.6,0.1> 11 22 31 <0.6,0.2,0.3> ((π ,π ,π ),{ π₯1 , π₯4 }),((π ,π ,π ),{ π₯3 , π₯4 })}. 11 21 32 <0.4,0.3,0.5> <0.7,0.3,0.2> 11 22 32 <0.4,0.4,0.2> <0.1,0.3,0.8> We have excluded those πβπ for which πΉ(π) is a null intuitionistic fuzzy set (similarly for those πβπ for which πΊ(π) is a null intuitionistic fuzzy set). The union and intersections of (πΉ,π) and (πΊ,π) are given by: (πΉ,π)βͺΜ(πΊ,π) ={((π ,π ,π ),{ π₯1 , π₯2 , π₯3 }),((π ,π ,π ),{ π₯2 }), 11 21 31 <0.5,0.2,0.3> <0.7,0.3,0.2> <0.8,0.6,0.1> 11 22 31 <0.6,0.2,0.3> ((π ,π ,π ),{ π₯3 , π₯4 }),((π ,π ,π ),{ π₯1 , π₯4 }), 12 21 31 <0.8,0.4,0.1> <0.1,0.5,0.5> 12 22 31 <0.5,0.2,0.3> <0.4,0.3,0.2> ((π ,π ,π ),{ π₯1 , π₯4 }),((π ,π ,π ),{ π₯3 , π₯4 }), 11 21 32 <0.4,0.3,0.5> <0.7,0.3,0.2> 11 22 32 <0.4,0.4,0.2> <0.1,0.3,0.8> ((π ,π ,π ),0 ),((π ,π ,π ),0 )}; 12 21 32 π 12 22 32 π and (πΉ,π)β©Μ(πΊ,π) ={((π ,π ,π ),{ π₯2 }),((π ,π ,π ),{ π₯2 })}. 11 21 31 <0.2,0.5,0.6> 11 22 31 <0.3,0.2,0.5> The differences (πΉ,π)\Μ(πΊ,π) and (πΊ,π)\Μ(πΉ,π) are the following (πΉ,π)\Μ(πΊ,π) Mujahid Abbas, Ghulam Murtaza, and Florentin Smarandache, Basic operations on hypersoft sets and hypersoft point Neutrosophic Sets and Systems, Vol. 35, 2020 413 ={((π ,π ,π ),{ π₯1 , π₯2 }),((π ,π ,π ),{ π₯2 })}; 11 21 31 <0.5,0.2,0.3> <0.6,0.15,0.2> 11 22 31 <0.3,0.4,0.6> (πΊ,π)\Μ(πΉ,π) ={((π ,π ,π ),{ π₯2 , π₯3 }),((π ,π ,π ),{ π₯2 })}. 11 21 31 <0.2,0.15,0.7> <0.8,0.6,0.1> 11 22 31 <0.5,0.4,0.3> Remark 3 There are four types of plithogenic hypersoft sets namely: plithogenic crisp hypersoft set, plithogenic fuzzy hypersoft set, plithogenic intuitionistic fuzzy hypersoft set, plithogenic neutrosophic hypersoft set. Here we discuss only plithogenic crisp hypersoft point whereas examples for other types of sets can be constructed in the similar way. Example 5 Let U={x ,x ,x ,x }. Define the attributes sets by: 1 2 3 4 πΈ ={π ,π },πΈ ={π ,π },πΈ ={π ,π }. 1 11 12 2 21 22 3 31 32 Suppose that π΄ ={π ,π },π΄ ={π ,π },π΄ ={π },and 1 11 12 2 21 22 3 31 π΅ ={π },π΅ ={π ,π },π΅ ={π ,π } 1 11 2 21 22 3 31 32 that is,. π΄ ,π΅ βπΈ for each π =1,2,3. π π π Let the plithogenic crisp hypersoft sets (πΉ,π) and (πΊ,π) be defined by (πΉ,π)={((π ,π ,π ),{π₯ (1,0,1),π₯ (1,1,1)}),((π ,π ,π ),{π₯ (0,0,1)}), 11 21 31 1 2 11 22 31 2 ((π ,π ,π ),{π₯ (1,1,0),π₯ (1,1,1)}),((π ,π ,π ),{π₯ (1,0,1),π₯ (0,1,0)})}. 12 21 31 3 4 12 22 31 1 4 and (πΊ,π)={((π ,π ,π ),{π₯ (1,1,1),π₯ (1,1,0)}),((π ,π ,π ),{π₯ (0,1,0)}), 11 21 31 2 3 11 22 31 2 ((π ,π ,π ),{π₯ (0,1,1),π₯ (1,1,1)}),((π ,π ,π ),{π₯ (1,1,1),π₯ (1,1,1)})}. 11 21 32 1 4 11 22 32 3 4 We have excluded all those πβπ for which πΉ(π) is a null plithogenic crisp set (similarly for those πβπ for which πΊ(π) is a null plithogenic crisp set). The union and intersections of (πΉ,π) and (πΊ,π) are given by: (πΉ,π)βͺΜ(πΊ,π)={((π ,π ,π ),{π₯ (1,0,1),π₯ (1,1,1),π₯ (1,1,0)}), 11 21 31 1 2 3 ((π ,π ,π ),{π₯ (0,1,1)}),((π ,π ,π ),{π₯ (1,1,0),π₯ (1,1,1)}), 11 22 31 2 12 21 31 3 4 ((π ,π ,π ),{π₯ (1,0,1),π₯ (0,1,0)}), 12 22 31 1 4 ((π ,π ,π ),{π₯ (0,1,1),π₯ (1,1,1)}),((π ,π ,π ),{π₯ (1,1,1),π₯ (1,1,1)}), 11 21 32 1 4 11 22 32 3 4 ((π ,π ,π ),0 ),((π ,π ,π ),0 )}; 12 21 32 ππΆ 12 22 32 ππΆ and (πΉ,π)β©Μ(πΊ,π)={((π ,π ,π ),{π₯ (1,1,1)}),((π ,π ,π ),0 )}. 11 21 31 2 11 22 31 ππΆ The differences (πΉ,π)\Μ(πΊ,π) and (πΊ,π)\Μ(πΉ,π) are the following (πΉ,π)\Μ(πΊ,π)={((π ,π ,π ),{π₯ (1,0,1)}),((π ,π ,π ),{π₯ (0,0,1)})}; 11 21 31 1 11 22 31 2 (πΊ,π)\Μ(πΉ,π)={((π ,π ,π ),{π₯ (1,1,0)}),((π ,π ,π ),{π₯ (0,1,0)})}. 11 21 31 3 11 22 31 2 Proposition 1 Let (πΉ,π¨) be a *-hypersoft set over π . Then the following holds; β 1. (πΉ,π)βͺΜΞ¦ =(πΉ,π); π Mujahid Abbas, Ghulam Murtaza, and Florentin Smarandache, Basic operations on hypersoft sets and hypersoft point Neutrosophic Sets and Systems, Vol. 35, 2020 414 2. (πΉ,π)β©ΜΞ¦ =Ξ¦ ; π π 3. (πΉ,π)βͺΜπΜ =πΜ ; π π 4. (πΉ,π)β©ΜπΜ =(πΉ,π); π 5. πΜ \Μ(πΉ,π)=(πΉ,π)π; π 6. (πΉ,π)βͺΜ(πΉ,π)π =πΜ ; π 7. (πΉ,π)β©Μ(πΉ,π)π =Ξ¦ . π Proof. We will prove only (i), (ii) and (v) and proofs of remaining are similar. (i) By the definition of union, we have (πΉ,π)βͺΜΞ¦ =(π»,π), π where π=π and π»(π)=πΉ(π)βͺ 0 =πΉ(π) for all πβπ. Hence (π»,π)=(πΉ,π). β β (ii) By the definition of intersection, we obtain that (πΉ,π)β©ΜΞ¦ =(π»,π), π where π=π and π»(π)=πΉ(π)β© 0 =0 for all πβπ. Hence (π»,π)=Ξ¦ . β β β π (v) By the definition of difference, we get πΜ \Μ(πΉ,π)=(π»,π), π where π=π and π»(π)=π\ πΉ(π)=πΉπ(π) for all πβπ. Hence (π»,π)=(πΉ,π)π. β 3. Hypersoft point In this section, we define hypersoft point in different frameworks and study some basic properties of such points in each setup. 3.1 Crisp hypersoft point Definition 9 Let π¨βπ¬, πΆβπ¨, and π₯ βπ. A hypersoft set (πΉ,π¨) is said to be a hypersoft point if πΉ(πΆβ²) is an empty set for every πΆβ² βπ¨\{πΆ} and πΉ(πΆ) is a singleton set. We will denote hypersoft point (πΉ,π¨) simply by π(πΆ,π₯). Definition 10 A hypersoft set (πΉ,π¨) is said to be an empty hypersoft point if πΉ(πΆ) is an empty set for each πΆβπ¨. We will denote an empty hypersoft set, corresponding to πΆ, by π(πΆ,β). As a matter of fact if (πΉ,π) is a null hypersoft set then for every πβπ it may be regarded as empty hypersoft set π(π,β). Definition 11 A hypersoft point π(πΆ,π₯) is said to belong to a hypersoft set (πΊ,π¨) if π(πΆ,π₯) βΜ (πΊ,π¨). We write it as π(πΆ,π₯) βΜ (πΊ,π¨). It is straightforward to check that the hypersoft union of hypersoft points of a hypersoft set (πΊ,π) returns the hypersoft set (πΊ,π), that is, (πΊ,π)=βͺΜ{π(π,π₯):π(π,π₯) βΜ (πΊ,π)}. We illustrate the above observation through the following example. Mujahid Abbas, Ghulam Murtaza, and Florentin Smarandache, Basic operations on hypersoft sets and hypersoft point Neutrosophic Sets and Systems, Vol. 35, 2020 415 Example 6 Let U={x ,x ,x ,x }, and (F,π) be as given in the example 1. Then the hypersoft points 1 2 3 4 of (F,π) are the following: π((π11,π21,π31),π₯1) ={((π ,π ,π ),{π₯ })}; 1 11 21 31 1 π((π11,π21,π31),π₯2) ={((π ,π ,π ),{π₯ })}; 2 11 21 31 2 π((π11,π22,π31),π₯2) ={((π ,π ,π ),{π₯ })}; 3 11 22 31 2 π((π12,π21,π31),π₯3) ={((π ,π ,π ),{π₯ })}; 4 12 21 31 3 π((π12,π21,π31),π₯4) ={((π ,π ,π ),{π₯ })}; 5 12 21 31 4 π((π12,π22,π31),π₯1) ={((π ,π ,π ),{π₯ })}; 6 12 22 31 1 π((π12,π22,π31),π₯4) ={((π ,π ,π ),{π₯ })}. 7 12 22 31 4 Moreover (πΉ,π)=π((π11,π21,π31),π₯1)βͺΜπ((π11,π21,π31),π₯2)βͺΜπ((π11,π22,π31),π₯2) 1 2 3 βͺΜπ((π12,π21,π31),π₯3)βͺΜπ((π12,π21,π31),π₯4)βͺΜπ((π12,π22,π31),π₯1)βͺΜπ((π12,π22,π31),π₯4). 4 5 6 7 Proposition 2 Let (πΉ,π¨),(πΉ ,π¨) and (πΉ ,π¨) be hypersoft sets over π. Then the following hold: 1 2 1. If (πΉ,π¨) is not a null hypersoft set, then (πΉ,π¨) contains at least one nonempty hypersoft point. 2. (πΉ ,π¨)βΜ (πΉ ,π¨) if and only if π(πΆ,π₯) βΜ(πΉ ,π¨) implies that π(πΆ,π₯) βΜ(πΉ ,π¨). 1 2 1 2 3. π(πΆ,π₯) βΜ(πΉ ,π¨)βͺΜ(πΉ ,π¨) if and only if π(πΆ,π₯) βΜ(πΉ ,π¨) or π(πΆ,π₯) βΜ(πΉ ,π¨). 1 2 1 2 4. π(πΆ,π₯) βΜ(πΉ ,π¨)β©Μ(πΉ ,π¨) if and only if π(πΆ,π₯) βΜ(πΉ ,π¨) and π(πΆ,π₯) βΜ(πΉ ,π¨). 1 2 1 2 5. π(πΆ,π₯) βΜ(πΉ ,π¨)\Μ(πΉ ,π¨) if and only if π(πΆ,π₯) βΜ(πΉ ,π¨) and π(πΆ,π₯) βΜ (πΉ ,π¨). 1 2 1 2 Proof. We will prove (1), (2) and (3). Proofs of (4) and (5) are similar to that of (3). (1) Suppose that (πΉ,π) is not a null hypersoft set, that is, πΉ(π)β β for some πβπ. Now if π βπ 0 is such that πΉ(π )β β, then for π₯ βπΉ(π ), there will be a hypersoft point π(π0,π₯) such that 0 0 π(π0,π₯) βΜ(πΉ,π). (2) Suppose that (πΉ ,π)βΜ (πΉ ,π) and π(π,π₯) βΜ(πΉ ,π). By the definition 11, we have 1 2 1 π(π,π₯) βΜ (πΉ ,π). 1 Thus π(π,π₯) βΜ (πΉ ,π)βΜ (πΉ ,π) 1 2 implies that π(π,π₯) βΜ(πΉ ,π). 2 Conversely suppose that π(π,π₯) βΜ(πΉ ,π) which implies that π(π,π₯) βΜ(πΉ ,π). By the 1 2 definition 11, we obtain that π(π,π₯) βΜ (πΉ ,π)forallπ(π,π₯) βΜ(πΉ ,π). 2 1 Thus we have (πΉ ,π)=βͺΜ{π(π,π₯):π(π,π₯) βΜ (πΊ,π)}βΜ (πΉ ,π). 1 2 (3) Suppose that π(π,π₯) βΜ(πΉ ,π)βͺΜ(πΉ ,π). It follows from the definition 11 that 1 2 π(π,π₯) βΜ (πΉ ,π)βͺΜ(πΉ ,π), 1 2 which implies that π₯ βπΉ (π)βͺ πΉ (π). Thus π₯ βπΉ (π) or πΉ (π). Hence we have 1 πΆ 2 1 2 π(π,π₯) βΜ(πΉ ,π)orπ(π,π₯) βΜ(πΉ ,π). 1 2 Conversely suppose that π(π,π₯) βΜ(πΉ ,π) or π(π,π₯) βΜ(πΉ ,π). This implies that π₯ βπΉ (π) or πΉ (π). 1 2 1 2 Thus π₯ βπΉ (π)βͺ πΉ (π) and so we have 1 πΆ 2 π(π,π₯) βΜ (πΉ ,π)βͺΜ(πΉ ,π). 1 2 Mujahid Abbas, Ghulam Murtaza, and Florentin Smarandache, Basic operations on hypersoft sets and hypersoft point Neutrosophic Sets and Systems, Vol. 35, 2020 416 3.2 Fuzzy hypersoft point Definition 12 Let π¨βπ¬, πΆβπ¨, and π₯ βπ . A fuzzy hypersoft set (πΉ,π¨) is said to be a fuzzy hypersoft πΉ point if πΉ(πΆβ²) is a null fuzzy set for every πΆβ² βπ¨\{πΆ} and πΉ(πΆ)(π¦)=0 for all π¦β π₯. We will denote (πΉ,π¨) simply by πΉπ(πΆ,π₯). Definition 13 A fuzzy hypersoft set (πΉ,π¨) is said to be a null fuzzy hypersoft point if πΉ(πΆ) is a null fuzzy set for each πΆβπ¨. We denote a null fuzzy hypersoft set, corresponding to πΆ, by πΉπ(πΆ,0πΉ). Note that if (πΉ,π) is a null fuzzy hypersoft set then for every πβπ, it can be regarded as null fuzzy hypersoft set πΉπ(π,0πΉ). Definition 14 A fuzzy hypersoft point πΉπ(πΆ,π₯) is said to belong to a fuzzy hypersoft set (πΊ,π¨) if πΉπ(πΆ,π₯) βΜ (πΊ,π¨). We write it as πΉπ(πΆ,π₯) βΜ(πΊ,π¨). It is straightforward to check that the fuzzy hypersoft union of fuzzy hypersoft points of a fuzzy hypersoft set (πΊ,π) returns the fuzzy hypersoft set (πΊ,π), that is, (πΊ,π)=βͺΜ{πΉπ(π,π₯):πΉπ(π,π₯) βΜ(πΊ,π)}. We illustrate this observation through the following example. Example 7 Let U={x ,x ,x ,x }, and (F,π) be as given in the example 2. Then some of the fuzzy 1 2 3 4 hypersoft points of (F,π) are given as: πΉπ((π11,π21,π31),π₯1) ={((π ,π ,π ),{π₯1})}; 1 11 21 31 0.5 πΉπ((π11,π21,π31),π₯1) ={((π ,π ,π ),{π₯1})}; 2 11 21 31 0.2 πΉπ((π11,π21,π31),π₯2) ={((π ,π ,π ),{π₯2})}; 3 11 21 31 0.7 πΉπ((π11,π22,π31),π₯2) ={((π ,π ,π ),{π₯2})}; 4 11 22 31 0.3 πΉπ((π12,π21,π31),π₯3) ={((π ,π ,π ),{π₯3})}; 5 12 21 31 0.8 πΉπ((π12,π21,π31),π₯4) ={((π ,π ,π ),{π₯4})}; 6 12 21 31 0.6 πΉπ((π12,π21,π31),π₯4) ={((π ,π ,π ),{π₯4})}; 7 12 21 31 0.9 πΉπ((π12,π22,π31),π₯1) ={((π ,π ,π ),{π₯1})}; 8 12 22 31 0.5 πΉπ((π12,π22,π31),π₯4) ={((π ,π ,π ),{π₯4})}. 9 12 22 31 0.4 Moreover we have (πΉ,π)=πΉπ((π11,π21,π31),π₯1)βͺΜπΉπ((π11,π21,π31),π₯1)βͺΜπΉπ((π11,π21,π31),π₯2) 1 2 3 βͺΜπΉπ((π11,π22,π31),π₯2)βͺΜπΉπ((π12,π21,π31),π₯3)βͺΜπΉπ((π12,π21,π31),π₯4) 4 5 6 βͺΜπΉπ((π12,π21,π31),π₯4)βͺΜπΉπ((π12,π22,π31),π₯1)βͺΜπΉπ((π12,π22,π31),π₯4). 7 8 9 Proposition 3 Let (πΉ,π¨),(πΉ ,π¨) and (πΉ ,π¨) be fuzzy hypersoft sets over π. Then the following hold: 1 2 1. If (πΉ,π) is not a null fuzzy hypersoft set, then (πΉ,π) contains at least one nonnull fuzzy hypersoft point. 2. (πΉ ,π)βΜ (πΉ ,π) if and only if πΉπ(π,π₯) βΜ(πΉ ,π) implies that πΉπ(π,π₯) βΜ(πΉ ,π). 1 2 1 2 Mujahid Abbas, Ghulam Murtaza, and Florentin Smarandache, Basic operations on hypersoft sets and hypersoft point