gistfile1.rb

# create a resolution (instrument. It observes facts about the world) without any externally visible fact
Facter.instrument(:network) do
  description "..."
  confine ...
  observe do
    ...
  end
end

# Create a specific composition, which is the final fact. Without the
# definition a resolution doesn't show up. We "define" a fact as the
# "interpretation" of the observed values from the available "instruments"
Facter.define(:network) do
  interpret do |available_instruments|
    available_instruments.inject({}) do |combined, r|
      r.value.merge(combined)
    end
  end
end

####################################################

# create a resolution with a basic composition (mimics current facter behavior)
Facter.add(:network) do
  description "..."
  confine ...
  observe do
    ...
  end
end

#the above is the equivalent of creating the instrument and a definition as
Facter.define(:network) do
  interpret do |available_instruments|
    real_instrument = available_instruments.find { |r| !r.value.nil? }
    real_instrument.value
  end
end

####################################################

# How do you define new interpretation of the instruments?
# Each definition can declare that it has a particular weight
Facter.define(:network) do
  description "This is a better combination of the network stuff"
  weight 500
  interpret do |available_instruments|
    available_instruments[Random.rand(10)].value
  end
end

I think that matches what I was getting at.