# Special Issue on Multi-Agent Systems
###### Abstract  
Multi-agent systems (MAS) are a class of systems in which multiple agents interact with each other and their environment to achieve a common or individual goal. Intelligent-agent-based systems are important because they allow for the creation of more flexible and adaptable systems that can effectively deal with complex and dynamic environments, and can improve their performance through learning and interaction with their surroundings. Multi-agent systems are used in a wide range of applications, such as simulation, industrial process control, smart cities, and cyber-physical systems, among others. One of the main advantages of multi-agent systems is their ability to adapt and make real-time decisions in dynamic and changing environments. Examples of multi-agent systems include distributed sensor networks, air-traffic control systems, and automated negotiation systems. In these systems, each agent has its own decision-making logic and can interact with other agents through a common communication platform. Overall, multi-agent systems are a powerful tool for addressing complex and distributed problems, and their use is increasingly prevalent in a variety of fields. This Special Issue on multi-agent systems presents 21 papers covering various key aspects in this area. First, a fundamental aspect of the development of multi-agent systems is the concept of interaction. Based on the need for interaction between intelligent computational entities, several works are proposed in this Special Issue. The work presented in [1] focuses on the problem of multi-agent tracking, where several tracking agents have to cooperate and interact with each other to track a maneuvering target. Related to tracking, but, in this case, of people, the work presented in [2] introduces a simple model to study the formation of lanes in crowds of individuals moving in opposite directions. Another related work is presented in [3], which addresses the multi-target binary classification problem by employing an ensemble of classification agents. Additionally, [4] presents a review regarding self-interested, non-cooperative agents. Specifically, the work focused on all the phases needed for non-cooperative, multi-agent planning environments. The formation of virtual organizations, such as groups or teams of agents, is another key aspect in the development of new proposals in multi-agent systems. In that sense, the work presented in [5] addresses the problem of multi-agent system design for organisations of agents acting in dynamic and uncertain environments, and demonstrates that the increased design time guidance available through the specification of organisational constructs and policies yields runtime flexibility in agent action. Another example is the work presented in [6], which proposes a Multiple Criteria Decision Analysis Framework that intends to overcome the limitations observed in group decisio- making. In [7], a novel method to simulate the realistic behavior of groups moving in a specific formation in a virtual environment, including other groups and obstacles, is presented. The formation problem is also considered in [8], which presents a control method for the formation problem of multi-robot systems. Lastly, in [9], a distributed, event-triggered control strategyis proposed to investigate the flocking problem in a multi-agent system. Flocking can be regarded as another form of cooperative control or group formation in MAS. The allocation of tasks or resources in distributed environments is another topic covered in this Special Issue. Specifically, the work presented in [10] proposes a computational resource distribution model to be used in distributed environments, which is capable of managing resources according to past experiences, and dynamically adjusting the resources allocated to each agent. Moreover, in [11], the authors focus on task allocation, in which a task allocation problem model, using agricultural plant protection environment as an example, is established.