With the advancement of virtual reality (VR), human-robot interaction within remote collaboration contexts has emerged as a pivotal research area. However, the nuanced interplay between the user's perspective and the robot's level of automation, and its subsequent impact on the operator's sense of agency (SoA), remains underexplored. This study investigates how perspective and collaboration mode-differentiated by the robot's level of automation-affect the SoA in VR-based human-robot collaboration. We implemented a 2 (perspective: first-person view[FPV] vs. third-person view[TPV]) × 3 (collaboration mode: Direct Remote Control, Supervisory Cooperation, Spectator Mode) experimental design. SoA was assessed via a multimodal approach, measuring both the explicit judgement of agency (JoA) and the implicit feeling of agency (FoA). The results revealed a dissociation between these two components: explicit JoA was dictated by the collaboration mode, with active modes yielding a higher explicit JoA than the passive Spectator Mode. In contrast, implicit FoA exhibited a significant interaction effect. Under FPV, the influence of collaboration mode was pronounced, where Direct Remote Control elicited the strongest FoA; however, under TPV, the differences among collaboration modes disappeared. The relationship between cybersickness and SoA was also explored. These findings suggest that SoA is not a unitary concept but a multifaceted experience, co-shaped by the user's perspective and their role as either a decision-maker or an executor. Furthermore, we investigate the relationship between cybersickness and SoA. Our study offers novel insights for the design of VR-based human-robot systems.

The method of local constraints attempts to describe context-free languages in an apparently context-sensitive form which helps to retain the intuitive insights about the grammatical structure. This form of description, while apparently context-sensitive is, in fact, context-free and allows a program derivation structure to be represented as a tree with additional constraints, thus allowing for the possibility of a correctness proof in the form of Knuthian semantics. A part of ALGOL 60 syntax has been restated as a grammar with local constraints. It is also shown that parsing of grammars with local constraints can be carried out by a suitable extension of Early's algorithm. Finally, the relationship of local constraints to the semantics of programs is discussed in Section 4 by considering some program transformations.