So far, the discussion has been around constraints applied during the package authoring process by modifying the package manifests. The administrator can also apply constraints to the system at runtime.
Using the pkg freeze command, the administrator can prevent a given package from being changed from either its current installed version, including time stamp, or a version specified on the command line. This capability is effectively the same as an incorporate dependency.
See the pkg(1) man page for more information about the freeze command.
To apply more complex dependencies to an image, create and install a package that includes those dependencies.