On σ‐porous sets in abstract spaces

The main aim of this survey paper is to give basic information about properties and applications of sigma-porous sets in Banach spaces (and some other infinite-dimensional spaces). This paper can be considered a partial continuation of the author's 1987 survey on porosity and sigma-porosity and therefore only some results, remarks, and references (important for infinite-dimensional spaces) are repeated. However, this paper can be used without any knowledge of the previous survey. Some new results concerning sigma-porosity infinite dimensional spaces are also briefly mentioned. However, results concerning porosity (but not sigma-porosity) are mentioned only exceptionally.