  [Background.] Empirical research in requirements engineering (RE) is a
constantly evolving topic, with a growing number of publications. Several
papers address this topic using literature reviews to provide a snapshot of its
"current" state and evolution. However, these papers have never built on or
updated earlier ones, resulting in overlap and redundancy. The underlying
problem is the unavailability of data from earlier works. Researchers need
technical infrastructures to conduct sustainable literature reviews. [Aims.] We
examine the use of the Open Research Knowledge Graph (ORKG) as such an
infrastructure to build and publish an initial Knowledge Graph of Empirical
research in RE (KG-EmpiRE) whose data is openly available. Our long-term goal
is to continuously maintain KG-EmpiRE with the research community to synthesize
a comprehensive, up-to-date, and long-term available overview of the state and
evolution of empirical research in RE. [Method.] We conduct a literature review
using the ORKG to build and publish KG-EmpiRE which we evaluate against
competency questions derived from a published vision of empirical research in
software (requirements) engineering for 2020 - 2025. [Results.] From 570 papers
of the IEEE International Requirements Engineering Conference (2000 - 2022), we
extract and analyze data on the reported empirical research and answer 16 out
of 77 competency questions. These answers show a positive development towards
the vision, but also the need for future improvements. [Conclusions.] The ORKG
is a ready-to-use and advanced infrastructure to organize data from literature
reviews as knowledge graphs. The resulting knowledge graphs make the data
openly available and maintainable by research communities, enabling sustainable
literature reviews.
