pkgdepgraph prints out a "dot" language specification of the inter-dependencies of your installed packages. The "dot" language is interpreted by the graphviz package to make graphs. There are several uses for such information. (1) A graphical representation of information is always good to look at. (2) The output itself can be sorted and filtered to provide a list of packages to delete in order that they can be rebuilt (to replace out-of-date components). (3) You can visually estimate the work involved in (or impact of) removing a given component in order to replace it.