Precedence

Precedence is a library that allows for the creation, manipulation and analysis of precedence networks.

Download and Install

Available as a RubyGem from Rubyforge. To install

$ gem install precedence

will fetch the latest gem from Rubyforge and install it.

Source can also be downloaded from rubyforge.org/projects/precedence.

Example Usage

require('precedence')

# Set up network
net = Precedence::Network.new('Begin','End')
net.new_activity('act-1-1') do |act|
	act.duration = 3
	act.description = 'System specification'
end
net.new_activity('act-1-2' do |act|
	act.duratiom = 2
	act.description = 'Review'
end
net.new_activity('act-1-3') do |act|
	act.duration = 2
	act.description = 'System re-specification'
end
net.new_activity('act-2-1') do |act|
	act.duration = 3
	act.description = 'Test tool design'
end
net.new_activity('act-2-2') do |act| 
	act.duration = 5
	act.description = 'Test tool implementation'
end
net.new_activity('act-3-1')
	act.duration = 3
	act.description = 'System design'
end
net.new_activity('act-3-2') do |act|
	act.duration = 12
	act.description = 'System implementation'
end
net.new_activity('act-2-3') do |act| 
	act.duration = 10
	act.description = 'System testing'
end
net.connect('act-1-1','act-1-2')
net.connect('act-1-2','act-1-3')
net.connect('act-1-3','act-3-1')
net.connect('act-1-2','act-2-1')
net.connect('act-2-1','act-2-2')
net.connect('act-2-2','act-3-2')
net.connect('act-3-1','act-3-2')
net.connect('act-3-2','act-2-3')
net.fix_connections!

# Generate a diagram
File.open('network.dot',File::CREAT|File::TRUNC|File::WRONLY) do |file|

file.puts(net.to_dot)

end
system("dot","-Tpng","-onetwork.png","network.dot")

# Perform some analysis of the activities
activity = net.activities['act-1-2']
activity.on_critical_path? # => true 
activity.earliest_start # => 3.0
activity.latest_finish # => 5.0
activity.total_float  # => 0 - activities on the critical path have no float

# Save the network to a YAML file
File.open('network.yaml',File::CREAT|File::TRUNC|File::WRONLY do |file|
	file.puts(net.to_yaml)
end

# Read the network from a YAML file
newNet = Precedence::Network.from_yaml(File.new('network.yaml',File::RDONLY))

Documentation

The Precedence API online documentation is available at precedence.rubyforge.org.

Refer to the CHANGELOG and TODO files for past changes and upcoming plans.

Credits

Farrel Lifson <farrel@lifson.info>

License

This software is made available under the BSD license.