dependency inheritance

[[LoN]Kamikaze]

I just created a port for http://sf.net/projects/bsdadminscripts , the
only dependency is

RUN_DEPENDS=            portupgrade:${PORTSDIR}/sysutils/portupgrade

Pkg_info shows the following for portupgrade:

# pkg_info -r 'portupgrade*'
Information for portupgrade-2.0.1_1,1:

Depends on:
Dependency: db4-4.0.14_1,1
Dependency: ruby-1.8.4_6,1
Dependency: perl-5.8.8
Dependency: ruby18-bdb4-0.5.7


The dependencies for bsdadminscripts are wrong, though:

# pkg_info -r bsdadminscripts-1.0
Information for bsdadminscripts-1.0:

Depends on:
Dependency: ruby18-bdb1-0.2.2
Dependency: openssl-0.9.8b
Dependency: ruby-1.8.4_6,1
Dependency: perl-5.8.8
Dependency: portupgrade-2.0.1_1,1


First of all I don't understand why it should have any dependencies
apart from portupgrade.
The second problem is that apart from ruby-1.8.4_6,1 and perl-5.8.8,
which were obviously inherited from portupgrade, why does it inherit the
wrong version of ruby-bdb and why doesn't it inherit bdb4?