The library contains functions to look the directory up that stores a package, to query metainformation about a package, and to retrieve dependency information about multiple packages. There is also a tool that allows the user to enter queries on the command-line. In order to simplify compilation and linkage, there are new frontends of the various OCaml compilers that can directly deal with packages. Together with the packages metainformation is stored. This includes a version string, the archives the package consists of, and additional linker options.
Packages can also be dependent on other packages.
There is a query which finds out all predecessors of a list of packages and sorts them topologically. The new compiler frontends do this implicitly. Metainformation can be conditional, i.e. depend on a set of predicates. This is mainly used to be able to react on certain properties of the environment, such as if the bytecode or the native compiler is invoked, if the application is multi-threaded, and a few more. If the new compiler frontends are used, most predicates are found out automatically.