Building syntax-aware editors for visual languages

Syntax-aware editors are a class of editors prompting users into writing syntactically correct programs by exploiting visual language syntax. They are particularly useful in those application domains where the way a visual symbol spatially relates to others depends from the context. This does not mean constraining users to enter only correct syntactic states in a visual sentence, rather it means detecting both syntax and potential semantic errors as early as possible, and providing error feedbacks in a non-intrusive way during editing. As a consequence, error handling strategies are an essential part of this editing style. In this work, we present a strategy for the automatic generation of syntax-aware visual language editors integrating incremental subsentence parsers into freehand editors. The proposed parsing strategy has turned out to be useful in many application domains involving spatial information systems, thanks to the possibility of interactively prompting feasible visual sentence extensions, and to the presence of a non-correcting error recovery strategy. A first experimental prototype implementing the whole approach has been embedded into the VLDesk system, and empirical studies have been performed in order to verify the performance and the effectiveness of the proposed approach.