New graphical and text-based notations for representing task decomposition hierarchies: towards improving the usability of an Ergonomics method

The representation of task decompositions, in the form of sub-goal hierarchies and their related sequencing triggering and exit conditions, lies at the heart of hierarchical task analysis (HTA) and related techniques. Analysis of the conventional graphical and text-based notations for these representations, using the principles of cognitive load theory, identifies a number of features that may give rise to difficulties when reading and constructing HTA representations. A revised graphical notation is presented, derived from similar notations that are used in the software engineering and human factors domains. An equivalent text-based notation is also presented to facilitate the representation of the task decomposition tabular format, where additional details of the task can be captured. It is suggested that the use of these revised notations could improve usability when constructing and interpreting graphical and tabular representations of hierarchical task decompositions.