box transparency 1 text "Module""Code"
arrow color yellow
unit1: sphere color red text "Unit""Test"
box transparency 1 text "Module""Code" at -10i, -5i, 1i
arrow color yellow
unit2: sphere color red text "Unit""Test"
box transparency 1 text "Module""Code" at -10i, -10i, 1i
arrow color yellow
unitN: sphere color red text "Unit""Test"
line dashed from unit2.bottom to unitN.top color yellow
sphererad = 2
integration: sphere color blue at 5i, -5i, 1i text "Integration""Test"
arrow text "Integration""Modules" color yellow
function: sphere color blue text "Function""Test"
arrow text "Functioning""System" color yellow 
performance: sphere color blue text "Performance""Test"
arrow text "Verified/Validated""Software" color yellow
acceptance: sphere color blue text "Acceptance""Test"
arrow color yellow text "Accepted""Sytem"
installation: sphere color blue text "Installation""Test"
down
arrow color yellow
box transparency 1 text "SYSTEM""IN""USE"
right
sys1: box transparency 1 at 5i, 2i, 1i text "System and""Program""Design""Specifications"
arrow from sys1.bottom to integration.top color yellow
sys2: box transparency 1 text "SYSTEM""Functional""Requirements" at 14i, 2i, 1i
arrow from sys2.bottom to function.top color yellow 
other_software: box transparency 1 text "Other""Software""Requirements" at 23i, 2i, 1i
arrow from other_software.bottom to performance.top color yellow
customer: box transparency 1 text "Customer""Requirements""Specification" at 32i, 2i, 1i
arrow from customer.bottom to acceptance.top color yellow 
user: box transparency 1 text "User""Environment" at 41i, 2i, 1i
arrow from user.bottom to installation.top color yellow
arrow from unit1.right to integration.left color yellow
arrow from unit2.right to integration.left color yellow
arrow from unitN.right to integration.left color yellow