  The Xacro XML macro language extends the Universal Robot Description Format
(URDF) and is part of a critical toolchain from geometric representations to
simulation, visualization, and system execution. However, members of the
robotics community, especially newcomers, struggle to troubleshoot and
understand the interplay between systems and the Xacro preprocessing pipeline.
To better understand how system developers struggle with Xacros, we manually
examine 712 Xacro-related questions from the question and answer site
http://answers.ros.org and find Xacro misunderstandings fit into 10 key
categories using a systematic, qualitative approach called Open Coding. By
examining the 'tags' applied to questions, we further find that Xacro problems
manifest in a befuddlingly broad set of contexts. This hinders onboarding and
complicates system developers' understanding of representations and tools in
the Robot Operating System. We aim to provide an empirical grounding that
identifies and prioritizes impediments to users of open robotics systems, so
that tool designers, teachers, and robotics practitioners can devise ways of
improving robot software tooling and education.
