  Understanding and interpreting human actions is a long-standing challenge and
a critical indicator of perception in artificial intelligence. However, a few
imperative components of daily human activities are largely missed in prior
literature, including the goal-directed actions, concurrent multi-tasks, and
collaborations among multi-agents. We introduce the LEMMA dataset to provide a
single home to address these missing dimensions with meticulously designed
settings, wherein the number of tasks and agents varies to highlight different
learning objectives. We densely annotate the atomic-actions with human-object
interactions to provide ground-truths of the compositionality, scheduling, and
assignment of daily activities. We further devise challenging compositional
action recognition and action/task anticipation benchmarks with baseline models
to measure the capability of compositional action understanding and temporal
reasoning. We hope this effort would drive the machine vision community to
examine goal-directed human activities and further study the task scheduling
and assignment in the real world.
