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The ability to infer and mediate intentions has been recognized as a crucial task in recent robotics research, where it is agreed that robots are required to be equipped with intentional mechanisms in order to participate in collaborative tasks with humans.

Reasoning about - or rather, perceiving - intentions enables robots to infer what other agents are doing, to communicate what are their plans, or to take proactive decisions. Intent recognition relates to several system requirements, such as the need of an enhanced collaboration mechanism in human-machine interactions, the need for adversarial technology in competitive scenarios, ambient intelligence, or predictive security systems.

When attempting to describe what an intention is, agreement exists to represent it as a plan together with the goal it attempts to achieve. Being compatible with computer science concepts, this representation enables to handle intentions with methodologies based on planning, such as the Planning Domain Description Language or Hierarchical Task Networks.

In this licentiate we describe how intentions can be processed using classical planning methods, with an eye also on newer technologies such as deep networks. Our goal is to study and define computational models that would allow robotic agents to infer, construct and mediate intentions. Additionally, we explore how intentions in the form of abstract plans can be grounded to sensorial data, and in particular we provide discussion on grounding over speech utterances and affordances, that correspond to the action possibilities offered by an environment.

With the advancement of Artificial Intelligence, intelligent computer programs known as agents are coming increasingly close to the life of human beings. In an optimistic view, predictions tell us that agents will be governing many machines such as phones, robots and cars. Agents will play an important role in our daily life, and because of this, it is becoming more and more relevant to provide them the capacity of interacting with their human users without requiring prior expert training, bur rather supporting understanding through common sense reasoning. Striving towards this objective, one important aspect of agents design is intentionality, that relates to their capacity of understanding goals and plans of their users, and to make theirs understood. The ability to reason on goals and objectives of themselves and others is especially important if the agents are autonomous such as in autonomous robots, because enabling them to interact with other agents by relying on their sensor data and internal computations only, and not on explicit data provided by their designer. 

Intentionality imbues agents with additional capacities supporting cooperative activities: if a helpful agent recognize an intention, it could proactively actuate interventions in an helpful way, such as giving advice. Alternatively, whenever the agent detects that its user is not understanding its objective it could communicate the mismatching information. As an illustrative example, let's consider the case of an autonomous car with a passenger on the road to his office. After checking the online maps the car identifies a traffic jam ahead, and to avoid it, autonomously decides to change its path mid-way by taking a less populated road. The behavior of the car is quite intelligent, however, if left unexplained, the change of intention would leave the passenger wandering  what is happening: he was on the main road to the office and suddenly the car turned left. This would at minimum force him to question the car what's going on. Rather, a continuous degree of understanding can be maintained if the car intelligently detect such mismatch of intentions by computing its passenger expectations, and thus preemptively communicate the new selected paths whenever required. 

This seemingly simple process of communicating changes in the intention, looks simple but it is a quite difficult one. It requires to reason on what are the intentions of the user, and how and when they should be aligned with those of the car, either explicitly through a process of explanation, or implicitly through a behavior that is interpretable by human beings.  To support these capacities it is becoming apparent how intelligent agents should leverage how we commonly think about things, referred to as common sense reasoning. Common sense reasoning relates to how we form conjectures based on what we observe, and agents forming conjectures in the same way could be better collaborators rather than those reasoning in other ways. In this thesis we utilized an established model for common sense reasoning known as Theory of Mind, of which the thesis will contain a brief introduction. 

By leveraging Theory of Mind and classical agent architectures, this thesis provides an initial formulation of a novel computational architecture capable of aggregating multiple tasks from intentionality, such as intent recognition, informative communication of intention and interpretable behavior. We refer to this model as the Mirror Agent Model, because envisioning the agent as interacting with a mirrored copy of itself whenever supporting intentionality. Inside the model expressing and recognizing intentions are two faces of the same coin and represent a dual to each other. This represents a step forward towards the unification in a single framework of many tasks related to intentionality, that are at the moment considered mostly independently inside the literature.

The thesis will firstly provide introductory chapters on agents, intentions and theory of mind reasoning, followed by a chapter describing the developed computational models. This chapter conceptually aggregates many of the algorithms from the papers and aims at providing an initial formulation of the Mirror Agent Model. Finally, the thesis will conclude with a summary of contributions and concluding remarks.