The automation of subject indexing at ZBW

Subject indexing, i.e., the enrichment of metadata records for textual resources with descriptors from a controlled vocabulary, is one of the core activities of libraries. However, due to the proliferation of digital documents it is no longer possible to annotate every single document intellectually, which is why we need to explore the potentials of automation. At ZBW the efforts to partially or completely automate the subject indexing process have started around the year 2000. In this talk we present the prototypical machine learning solutions that we developed in an applied research project over the past few years, the roadblocks and lessons learned, and next steps / our vision for the future