Abstract: In this talk, we will focus on the outer automorphism groups of right-angled Artin groups. I will introduce these groups from a group-theoretic perspective, covering aspects such as finite generation and the standard representation. Moreover, the presence or absence of a separating intersection of links (or SIL-pairs, for short) plays a crucial role in determining the structural behavior of the outer automorphism group. Regarding the notion of SIL-pairs, we will define a maximal SIL-pair system to combine the parts of graphs that generate SIL-pairs, so that one can decompose defining graphs to understand the group structures of the outer automorphism groups of right-angled Artin groups. We will also see how maximal SIL-pair systems help us to detect acylindrical hyperbolicity of a subgroup of the outer automorphism group of a right-angled Artin group, called the pure symmetric outer automorphism group.