when referring to Xfce use "Xfce Desktop Environment" or "Xfce" (note the capitalization)
subpackages should not repeat the summary but have a one of their own, for development or documentation a generic "Development Files for Foo" or "Documentation for Foo" suffices
the description should contain a summary of what the package contains which is meaningful to consumers
do not repeat the main package description in subpackages but provide a separate description which may refer to the main package, e.g. "This package contains development files needed for developing applications based on foo." or "This package provides the HTML documentation for foo."