What are scientifically valuable developments for ALMA enhancement?

The Atacama Large Millimeter/submillimeter Array (ALMA) is already producing a growing number of impressive and scientifically compelling results during its first two years of operation as the most powerful mm/submm interferometer in the world. However, ALMA still has some scientific weak points due to the technological limitations. In order to maintain ALMA as the state-of-the-art facility over the course of its projected life of 30+ years, continuing technical upgrades and developments for new capabilities are essential. We have already performed future development studies and projects for ALMA enhancement, which are the main development focus for the next 5 - 10 years. We should now start the discussion of the technical requirements and the potential science achievable with larger scale developments which are envisioned in the next 10 - 20 years, because it is emphasized that the larger scale project will likely result in higher impact, groundbreaking ALMA science in the year 2034 and beyond.