# An Activity Theory-Based Approach for Context Analysis, Design and Evolution
## 1 Introduction
### Activity Theory: Essentials  
Activity theory was born with the studies of [PERSON] and [PERSON] on historical-cultural Psychology, carried out in the Soviet Union in the 1920s [21]. Activity theory conceptualizes a human activity as the unit of analysis. In general, people have an informal idea of what an \"_activity_\" is, but in activity theory, \"_human activity_\" refers to any action that acquires its form and meaning when it is performed with a purpose, or goal, in mind. For example, software development is a human activity performed by a team of developers. Each individual developer creates and builds the software by writing, debugging, and executing code. Their goal is to obtain a coherent product that is useful to users and that other developers can understand and improve on. In classical activity theory, human activity is divided into three components: subject, tool, and object [30]. The subject is the person who pursues a particular goal. This goal is the object of the activity and represents a prospective outcome that motivates and directs the subject, around which the activity is coordinated and crystallizes in a final form, when completed [31]. The object, then, defines the target, objective, or purpose of the activity. Objects in activity theory are what distinguish one activity from another. In this regard, this object of activity should not be understood as a physical object or a tangible \"_thing_\". The other classic element in activity theory, the tool, is the mediation mechanism or device through which an action is executed in order to achieve the object. Tools can be physical (e.g., hammer, pencil, scissors, etc.) or mental (e.g., checklists, procedures, ideas, knowledge, experience, etc.) [32]. Consequently, the tools provide a model based on the experiences of other subjects who made similar activities, which can be improved to make them more useful or efficient. Eventually, [PERSON] [33] introduced some modifications to [PERSON]'s and [PERSON]'s original theory, providing additional elements of analysis. The first of these elements is the set of rules or conditions that help determine how subjects can act. Rules are the result of social elaboration and are subject to social conditioning. Rules concern any guidelines, codes, heuristics, or conventions that guide activities and behaviors. The second element added by [PERSON] is the division of labor, which accounts for the distribution of actions and operations among a community of coworkers. It can be conceptualized as a hierarchical structure that organizes and supports the activity, balancing the tasks and actions of the activity among different subjects. Both the rules and the division of labor influence and shape a social plane known as community. Through it, groups of activities and teams of subjects can be analyzed [33]. Finally, there is the outcome element that states what the activity system produces, desired or undesired. It acts as an indicator to measure the degree of achievement of the object of the activity. For example, the object of a particular participant in a sporting activity, such as a marathon, can be \"_participate_\", while the outcome can take the form of \"_win_\", \"_lose_\", \"_complete the run_\", etc. A generic activity system is represented in Figure 1 as a triangle of triangles [31]. In this picture, the subject, the object, and the community are the core elements, shown as a sub-triangle within the bigger triangle. The outer elements (vertexes of the big triangle) act as intermediates between the main core ones; these intermediates are the tools, the rules, and the division of labor. The tools intermediate between the subject and the object, the Rules intermediate between the subject and the Community and, finally, the Division of Labor mediates between the Community and the object of activity. This triangle representation (Figure 1) allows a distributed view rooted in the nature of the activities and environments in which they occur.