End User Development for Extended Reality

In recent years, consumer interest in Virtual Reality (VR), Augmented Reality (AR), and Mixed Reality (MR) is increasing, thanks to improved technology and wider availability. These XR technologies are not just for gaming; they're also being used effectively in education and vocational training. Literature suggests that as XR becomes more accessible, users will increasingly require more control over the content they create and experience within these immersive environments, mirroring the evolution seen with technologies like the Internet of Things and web content management. Creating and customizing content for Immersive XR environments is often limited to technically skilled individuals. This is similar to how the creation of web content was limited before the development of Content Management Systems, such as WordPress. In this thesis End-User Development (EUD) has been proposed as a way to empower non-programmers to design and build functional XR experiences. This set of techniques "allow users of software systems, who are acting as non-professional software developers, at some point to create, modify, or extend a software artifact". Similarly, research has been conducted to explore methods for guiding users without prior XR experience in effectively interacting with these systems, further supporting the goal of making XR development accessible to a broader audience. The first work proposes a solution for supporting end users in configuring Virtual Reality environments by exploiting reusable templates created by experts. In the work they are defined the roles participating in the environment development and the means for delegating part of the behaviour definition to the end users. The focus is in particular on enabling end users to define the environment behaviour. The solution exploits a taxonomy defining common virtual objects having high-level actions for specifying event-condition-action rules readable as natural language sentences. End users exploit such actions to define the environment behaviour. The second part presents a system for assisting novice developers in learning how existing VR environments have been developed, so they can exploit these notions to adapt and implement their own systems. The proposed approach also employs a model abstraction that harmonizes existing XR toolkit implementations, offering an interface that facilitates toolkit-agnostic interaction comprehension, particularly for novices. The third part focuses on a meta-level user interface designed to guide users in multimodal interactions within VR environments. The system enhances task discoverability, provides feedforward on interaction results, and dynamically recommends interaction modalities based on application context, user preferences, and designer inputs. The last part presents a novel work that adapts the previous system, geared towards showing direct feedforward representations of the interactions described in the user interface. These representations can be adapted through a dedicated user interface, or through alternative options made by the creator of the procedure. These adaptations can be also suggested at design time and triggered to be set up at runtime by specialized LLM models.