  With the rapid development of advanced electromagnetic manipulation
technologies, researchers and engineers are starting to study smart surfaces
that can achieve enhanced coverages, high reconfigurability, and are easy to
deploy. Among these efforts, simultaneously transmitting and reflecting
intelligent omni-surface (STAR-IOS) is one of the most promising categories.
Although pioneering works have demonstrated the benefits of STAR-IOSs in terms
of its wireless communication performance gain, several important issues remain
unclear including practical hardware implementations and physics-compliant
models for STAR-IOSs. In this paper, we answer these pressing questions of
STAR-IOSs by discussing four practical hardware implementations of STAR-IOSs,
as well as three hardware modelling methods and five channel modelling methods.
These discussions not only categorize existing smart surface technologies but
also serve as a physicscompliant pipeline for further investigating the
STAR-IOSs.
