The Challenges in Metadata Management: 20+Years of ESO Data

The European Southern Observatory Science Archive Facility has been in operations for more than 20 years. It contains data produced by ESO telescopes as well as the metadata needed for characterizing and distributing those data. This meta data is used to build the different archive services provided by the Archive. Over these years, services have been added, modified or even decommissioned creating a cocktail of new, evolved and legacy data systems. The challenge for the Archive is to harmonize the differences of those data systems to provide the community with a homogeneous experience when using ESO data. In this paper, we present ESO experience in three particular challenging areas. First discussion is dedicated to the problem of metadata quality over the time, second discusses how to integrate obsolete data models on the current services and finally we will present the challenges of ever growing databases. We describe our experience dealing with those issues and the solutions adopted to mitigate them.