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Large sky surveys and the data they generate have an enormous scientific potential as they enable new scientific research and astronomical discoveries. By definition, astronomical data are irreplaceable and unrepeatable. As such, making astronomical data publicly available in a structured, intelligible format is of fundamental importance to enable both scientific transparency and long term data curation and preservation \cite{King95}.    The physical and astronomical sciences have a well established reputation for being disciplines with a strong culture of data sharing. Astronomy has pioneered Open Access to both publications and data. In fact, the data generated by large sky surveys, such as those indicated above, are collected under national grants (e.g., NASA), archived by national institutions (e.g., the Space Telescope Science Institute, STSci), and made publicly available to anyone (e.g., \url{http://archive.stsci.edu/}). The fact that astronomical data from large surveys are publicly available is remarkable, but by no means surprising. Astronomers collect data about the universe. As such, they feel a moral obligation to share collected data openly. Moreover, these data are collected under national programs that require data to be made openly available.     Despite its sheer volume, the data collected in the context of large surveys, however, represent only a portion of all the data generated in astronomy. If we imagine all generated data in astronomy to be a pyramid with different levels of data \cite{Borgman}, from raw data  Because of their sheer size, however, astronomical data are often left out