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In Example 1 of [1], the authors concluded that \((X,\tau ,E)\) is a soft topological space over the universe \(X=\{h_1,h_2,h_3,h_4\}\) and the set of parameters \(E=\{e_1,e_2,e_3\}\). Actually, their conclusion is not correct where \((F_1,E)\), \((F_2,E)\in \tau \) leads to \((F_1,E){\tilde{{\cap }}}(F_2,E)\not \in \tau \) and \((F_1,E){\tilde{{\cup}}}(F_2,E)\not \in \tau \). Also, this is achieved for another soft sets like \((F_1,E)\) and \((F_{14}, E)\). As a result of this flaw, Examples 2, 6, 7 and 8 in [1] are not correct. Examples 1 and 2 achieve the goal of Examples 1 and 2 in [1].
Let \(X=\{h_1,h_2,h_3,h_4\}\) and \(E=\{e_1,e_2\}\).
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(1)
If \(\tau _1=\{\tilde{{\emptyset}},{\tilde{{X}}},(F_1,E), (F_2,E), (F_3,E)\}\) is a soft topology where \((F_1,E)\), \((F_2,E)\), \((F_3,E)\) and (F, E) are soft sets over X defined by:
$$\begin{aligned} \begin{array}{ll} F_1(e_1)=\{h_1\}, &{} F_1(e_2)=\{h_1\}, \\ F_2(e_1)=\{h_2\}, &{} F_2(e_2)=\{h_2\}, \\ F_3(e_1)=\{h_1,h_2\}, &{} F_3(e_2)=\{h_1,h_2\}. \\ \end{array} \end{aligned}$$and
$$\begin{aligned} F(e_1)=\{h_1,h_3\},\quad F(e_2)=\{h_1,h_3\}. \end{aligned}$$Then (F, E) is sb-open set but not sp-open set.
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(2)
If \(\tau _2=\{{\tilde{{\emptyset }}},{\tilde{{X}}},(F_1,E), \dots , (F_7,E)\}\) is a soft topology where \((F_1,E)\), …, \((F_7,E)\) and (H, E) are soft sets over X defined by:
$$\begin{aligned} \begin{array}{ll} F_1(e_1)=\{h_1,h_2\}, &{} F_1(e_2)=\{h_1,h_2\},\\ F_2(e_1)=\{h_2\}, &{} F_2(e_2)=\{h_1,h_3\},\\ F_3(e_1)=\{h_2,h_3\}, &{} F_3(e_2)=\{h_1\},\\ F_4(e_1)=\{h_2\}, &{} F_4(e_2)=\{h_1\},\\ F_5(e_1)=\{h_1,h_2\}, &{} F_5(e_2)=X,\\ F_6(e_1)=X, &{} F_6(e_2)=\{h_1,h_2\},\\ F_7(e_1)=\{h_2,h_3\}, &{} F_7(e_2)=\{h_1,h_3\}. \end{array} \end{aligned}$$and
$$\begin{aligned} H(e_1)=\emptyset ,\quad H(e_2)=\{h_1\}. \end{aligned}$$Then (H, E) is sb-open set but not ss-open set.
Let \({\mathbb {R}}\) be the set of the real numbers and \(E=\{e\}\) be the parameters set. Define the usual soft topology over \({\mathbb {R}}\) with respect to E. Let (F, E) be a soft set over \({\mathbb {R}}\) defined by \(F(e)=[0,1)\cap {\mathbb {Q}}\) where \({\mathbb {Q}}\) is the set of rational numbers, then (F, E) is s\(\beta \)-open set but not sb-open set.
The following two examples meet the purpose of Examples 6, 7 and 8 in [1].
Let \(X=\{h_1,h_2,h_3,h_4\}\), \(Y=\{m_1,m_2,m_3,m_4\}\), \(E=\{e_1,e_2\}\) and \(K=\{k_1,k_2\}\).
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1.
If \((X,\tau _1,E)\) is a soft topological space defined as in Example 1(1), \((Y,\nu _1,K)\) be a soft topological space defined over Y where \(\nu _1=\{{\tilde{{\emptyset}}},{\tilde{{Y}}}, (L_1,K)\}\) and \((L_1,K)\) is a soft set on Y defined by:
$$\begin{aligned} L_1(k_1)=\{m_1,m_2\},\quad L_1(k_2)=\{m_1,m_2\}. \end{aligned}$$Let \(f:(X,\tau _1,E)\rightarrow (Y,\nu _1,K)\) be a soft function defined by
$$\begin{aligned} u(h_1)=m_2,\quad u(h_2)=m_4,\quad u(h_3)=m_1,\quad u(h_4)=m_3, \end{aligned}$$$$\begin{aligned} p(e_1)=k_2,\quad p(e_2)=k_1. \end{aligned}$$Then f is soft b-continuous function but not soft pre-continuous.
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2.
If \((X,\tau _2,E)\) is a soft topological space defined as in Example 1(2), \((Y,\nu _2,K)\) is a soft topological space defined over Y where \(\nu _2=\{{\tilde{{\emptyset}}},{\tilde{{Y}}}, (L_2,K)\}\) and \((L_2,K)\) is a soft set on Y defined by:
$$\begin{aligned} L_2(k_1)=\{m_2\},\quad L_2(k_2)=\emptyset . \end{aligned}$$Let \(f:(X,\tau _1,E)\rightarrow (Y,\nu _2,K)\) be a soft function defined as in (1), then f is soft b-continuous function but not soft semi-continuous.
Let \({\mathbb {R}}\) be the set of real numbers, \(E=\{e\}\), \(K=\{k\}\), \(({\mathbb {R}},\mathcal {U}, E)\) be the usual soft topology and \(({\mathbb {R}},\mathcal {V},K)\) be a soft topology over \({\mathbb {R}}\) such that \(\mathcal {V}=\{{\tilde{{\emptyset}}},{\tilde{{R}}}, (M,K)\}\) where (M, K) is a soft set defined over \({\mathbb {R}}\) by \(M(k)=[0,1)\cap {\mathbb {Q}}\). Define the maps \(u:{\mathbb {R}}\rightarrow {\mathbb {R}}\) and \(p:E\rightarrow K\) by
and \(p(e)=k\). Then \(f^{-1}(M,K)=(H,E)\) where \(H(e)=[0,1)\cap {\mathbb {Q}}\). Thus f is soft \(\beta \)-continuous function but not soft b-continuous.
References
Akdaǧ, Metin, Ozkan, Alkan: Soft \(b\)-open sets and soft \(b\)-continuous functions. Math. Sci. 8, 124 (2014)
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This comment refers to the original article with article doi:10.1007/s40096-014-0124-7 (Math Sci (2014) 8:124).
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Ghareeb, A. Comments on “Soft b-open sets and soft b-continuous functions, Math. Sci. (2014) 8:124”. Math Sci 10, 63–64 (2016). https://doi.org/10.1007/s40096-016-0174-0
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DOI: https://doi.org/10.1007/s40096-016-0174-0