The conditional dependency has a predicate attribute and an fmri attribute. If the package specified in the value of the predicate attribute is present on the system at the specified or greater version, the conditional dependency is treated as a require dependency on the package in the fmri attribute. If the package specified in the predicate attribute is not present on the system or is present at a lower version, the conditional dependency is ignored.
The conditional dependency is most often used to install optional extensions to a package if the requisite base packages are present on the system.
For example, an editor package that has both X11 and terminal versions might place the X11 version in a separate package, and include a conditional dependency on the X11 version from the text version with the existence of the requisite X client library package as the predicate.
An example conditional dependency is:
depend type=conditional fmri=library/python-2/pycurl-26 \
predicate=runtime/python-26