On constructions of greedoids

الملخص EN

In this paper we discuss four basic constructions of greedoids namely, deletion, contraction, direct sum and ordered sum.

We show the operations of deletion and contraction commute and the direct sum and ordered sum of greedoids G/ and G2 are interval greedoids if and only if G, and G: are both interval greedoids.

We also give a necessary and sufficient condition for the direct sum and ordered sum of balanced greedoids to be balanced.