In this paper, we introduce the concept of sum of soft topological spaces using pairwise disjoint soft topological spaces and study its basic properties. Then, we define additive and finitely additive properties which are considered a link between soft topological spaces and their sum. In this regard, we show that the properties of being p-soft T i , soft paracompactness, soft extremally disconnectedness, and soft continuity are additive. We provide some examples to elucidate that soft compactness and soft separability are finitely additive; however, soft hyperconnected, soft indiscrete, and door soft spaces are not finitely additive. In addition, we prove that soft interior, soft closure, soft limit, and soft boundary points are interchangeable between soft topological spaces and their sum. This helps to obtain some results related to some important generalized soft open sets. Finally, we observe under which conditions a soft topological space represents the sum of some soft topological spaces.

The concept of soft sets was proposed as an effective tool to deal with uncertainty and vagueness. Topologists employed this concept to define and study soft topological spaces. In this paper, we introduce the concepts of soft SD-continuous, soft SD-open, soft SD-closed and soft SD-homeomorphism maps by using soft somewhere dense and soft cs-dense sets. We characterize them and discuss their main properties with the help of examples. In particular, we investigate under what conditions the restriction of soft SD-continuous, soft SD-open and soft SD-closed maps are respectively soft SD-continuous, soft SD-open and soft SD-closed maps. We logically explain the reasons of adding the null and absolute soft sets to the definitions of soft SD-continuous and soft SD-closed maps, respectively, and removing the null soft set from the definition of a soft SD-open map.

Hypersoft set theory is an extension of soft set theory and is a new mathematical tool for dealing with fuzzy problems; however, it still suffers from the parametric tools’ inadequacies. In order to boost decision-making accuracy even more, a new mixed mathematical model called the bipolar hypersoft set is created by merging hypersoft sets and bipolarity. It is characterized by two hypersoft sets, one of which provides positive information and the other provides negative information. Moreover, some fundamental properties relative to it such as subset, superset, equal set, complement, difference, relative (absolute) null set and relative (absolute) whole set are defined. Furthermore, some set-theoretic operations such as the extended intersection, the restricted union, intersection, union, AND-operation and OR-operation of two bipolar hypersoft sets with their properties are discussed and supported by examples. Finally, tabular representations for the purposes of storing bipolar hypersoft sets in computer memory are used.

Molodtsov [D. Molodtsov, Global optimization, control, and games, III, Comput. Math. Appl., 37 (1999), 19-31] studied the concept of soft sets. The concept of soft sets is introduced as a general mathematical tool for dealing with uncertainty. In this paper, we give some basic relations about different classes of soft sets and soft closure operator. The purpose of this paper is to introduce soft extremally disconnected spaces via soft sets. Furthermore, some relations of soft sets and soft closure via soft extremally disconnected spaces have been investigated.

This paper introduces some new classes of functions called γ-P Scontinuous, β-P S-open and β-P S-closed using γ-P S-open set and γ-P Sclosed set. In addition, some properties and characterizations of these functions are given. The result shows that γ-P S-continuous function and γ-continuous function are independent.

The basic of bipolar soft set theory stands for a mathematical instrument that bringstogether the soft set theory and bipolarity. Its definition is based on two soft sets, a set thatprovides positive information and other that gives negative. This paper mainly aims at defininga new bipolar soft generalized topological space; setting out of the point that the collection ofbipolar soft sets forms the basis for the definition of the new concept is defined. Added to that,an investigation has been made of the four concepts of bipolar soft generalized, namely g-interior,g-closure, g-exterior and g-boundary. Furthermore, the main properties of bipolar soft generalizedtopological space (BSGT S) are established. This paper also attends to the discussion of therelations between these new definitions and the application of the given bipolar soft generalizedtopological spaces in a decision-making problem where an algorithm for this application has beensuggested. Finally, to clarify and substantiate what the current work subsumes, some exampleshave been provided.

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The authors of [13] formulated a soft topological ordered spaces concept and then they established and studied some ordered mappings [14]. In the present work, we define new ordered mappings via soft topological ordered spaces based on soft β-open sets, namely soft xβ-continuous, soft xβ-open, soft xβ-closed and soft xβ-homeomorphism mappings, for x ∈ {I, D, B}. We give various characterizations of each one of the introduced soft mappings. One of the most important obtained results is that an extended soft topologies notion guarantees the equivalent  between the soft mappings initiated herein and their counterparts of mappings on topological ordered spaces. We provide several interesting examples to examine the relationships among these soft mappings.