In this paper, we present a formal representation of an Augmentative and Alternative Communication (AAC) application, called Volo, for users with Autism Spectrum Disorders (ASD). We discuss existing AAC applications and present a formal visualisation model of Volo based on zz-structures, hyper-orthogonal, non-hierarchical structures for storing, linking and manipulating data. To the best of our knowledge, this is the first work that tries to give a formal model to AAC techniques. We finally present the prototype of this new Volo application.
