In simulations of compact stars, binary mergers and core-collapse
supernovae an equation of state (EoS) is needed to close the system of
combined Einstein and hydrodynamics equations. I will discuss
requirements for such an equation of state. Then I will present the
data base Compose, part of the PHAROS project, which contains EoS and
related data ready for use in simulations. I will show some examples
of results obtained with publicly available data and the computational
tools from CompOSE.