A dependency graph is a (usually automatically generated) directed graph of dependencies. These are often useful to automated installers, which walk the graph looking for uninstalled but needed software packages. A tree structure or directed acyclic graph place restrictions on what dependencies are allowed for any given node. This article just presents the basic definitions. ... In computer science, coupling or dependency is the degree to which each program module relies on each other module. ... An installation program or installer is a computer program that installs files, such as applications, drivers, or other software, onto a computer. ... A software package is a bundle of one or several files that either are necessary for the distribution and installation of a computer program, or which will upgrade and install additional features for an existing program already installed on a computer. ... A tree structure is a way of representing the hierarchical nature of a structure in a graphical form. ... A simple directed acyclic graph In computer science and mathematics, a directed acyclic graph, also called a dag or DAG, is a directed graph with no directed cycles; that is, for any vertex v, there is no nonempty directed path that starts and ends on v. ...