The lower independence number of a graph
is the minimum size of a maximal
independent vertex set in
. The lower indepedence number is equivalent to the independent
domination number (i.e., the minimum size of an independent
dominating set; cf. Crevals and Östergård 2015, Ilić and Milošević
2017).
The (upper) independence number may be similarly defined as the largest size of an independent
vertex set in (Burger et al. 1997).
The lower irredundance number , lower domination number
,
lower independence number
, upper independence
number
,
upper domination number
, and upper
irredundance number
satsify the chain of inequalities
(Burger et al. 1997).