# SIoT: A New Strategy to Improve the Network Lifetime with an Efficient Search Process
## 1 Introduction  
The term Internet of Things (IoT) has been known for the last few years. IoT describes a vision where every object becomes a part of the Internet, and has been recognized as one of the major technological revolutions of this century [1, 2]. IoT allows things and people to be connected anytime, from anyplace, with anything and anyone, preferably using any network/path and any service [3]. The fundamental goal is to create a more desirable world for human beings, where objects and things around them know what they want, what they like, and what they need and act accordingly without any explicit instructions [4]. The outspread use of IoT in various domains, such as transportation [5, 6, 7], health [8, 9, 10], manufacturing [11, 12, 13], and other fields aims to create a new environment of applications which will influence our lives [14, 15]. The search for a specific service is a crucial challenge such as battery energy, interoperability, reliability, scalability, availability, etc. Moreover, network lifetime is the total amount of time to maintain its full functionality [16], it is constrained by the battery of nodes [17]. These constraints that are related to the nature of a node and are named as the \"_Capability_\" of the node. A capability indicates the capacity to perform a particular service, task, activity, or function [18, 19, 20]. Due to the rapid technology and development that are happening in our social lives, a new concept named Social Internet of Things (SIoT) has been proposed [21, 22]. It is an integration of social network and Internet of Things, introducing a new vision of socialrelationships among different devices/things, independently from the fact that they belong to the same or to different platforms owned and managed by different organizations. This vision makes all the IoT devices ready to cooperate with others and create relationships among them as human beings do. According to the growth of intelligent devices especially in smart cities, the social Internet of Things offers a new mechanism of communication among nodes, in a distributed manner, with only local information. This mechanism allows the nodes to search for services and resources by themselves instead of the central systems such as servers, cloud computing, etc. Figure 1a illustrates the concept of SIoT, there are two entities: object and service. These entities can provide and consume services and/or data. In this sense, services themselves can consume data produced by other services to form a composite service or to be used for other objectives. Figure 1b shows a mechanism of service search in SIoT, where the communication is in a decentralized manner. When a node receives a request that includes the requirements of a customer node, it verifies if it can respond to this request by itself or by its friends, elsewhere it will be transmitted to a given node until the provider node is found. The similarity between the request requirements and service is divided into two types that are proximity and point. The point type is the provider node should respond strictly to the declared requirements such as monitoring the temperature at a fixed location, while in the proximity type is the provider node could respond flexibly to the declared requirements such as monitoring the temperature at a specific area. Figure 1: Concept of the social internet of things (SIoT). According to [23], there are five types of friendship in the SIoT, namely:  
* **Parental Object Relationship (POR):** It is established among similar objects. They have the same producer, model, and production batch. * **Co-location Object Relationship (C-LOR):** It is established among heterogeneous or homogenous objects that share the same location. * **Ownership Object Relationship (OOR):** It is established if the objects are owned by the same user. * **Co-work Object Relationship (CWOR):** It is established when two or more devices collaborate to accomplish a common goal.