  In this White Paper, we present recommendations for the scientific community
and funding agencies to foster the infrastructure for a collaborative
multi-messenger and time-domain astronomy (MMA/TDA) ecosystem. MMA/TDA is
poised for breakthrough discoveries in the coming decade. In much the same way
that expanding beyond the optical bandpass revealed entirely new and unexpected
discoveries, cosmic messengers beyond light (i.e., gravitational waves,
neutrinos, and cosmic rays) open entirely new windows to answer some of the
most fundamental questions in (astro)physics: heavy element synthesis, equation
of state of dense matter, particle acceleration, etc. This field was
prioritized as a frontier scientific pursuit in the 2020 Decadal Survey on
Astronomy and Astrophysics via its "New Windows on the Dynamic Universe" theme.
MMA/TDA science presents technical challenges distinct from those experienced
in other disciplines. Successful observations require coordination across
myriad boundaries -- different cosmic messengers, ground vs. space,
international borders, etc. -- all for sources that may not be well localized,
and whose brightness may be changing rapidly with time. Add that all of this
work is undertaken by real human beings, with distinct backgrounds,
experiences, cultures, and expectations, that often conflict. To address these
challenges and help MMA/TDA realize its full scientific potential in the coming
decade (and beyond), the second in a series of community workshops sponsored by
the U.S. National Science Foundation (NSF) and NASA titled "Windows on the
Universe: Establishing the Infrastructure for a Collaborative Multi-Messenger
Ecosystem" was held on October 16-18, 2023 in Tucson, AZ. Here we present the
primary recommendations from this workshop focused on three key topics --
hardware, software, and people and policy. [abridged]
