A virtual appliance construction tool allows a user to select using a user interface functional information for a virtual appliance to generate a functional model of the virtual appliance. A knowledge base of configuration units is then queried to determine which configuration units are needed to satisfy the functional model. Note the configuration units include not only functional information, but virtualization information as well. The configuration units are then packaged into a virtual appliance blueprint, which is used to generate a certified virtual appliance. In this manner the user need not have extensive knowledge or training regarding virtualization because the virtualization information is selected automatically based on which configuration units provide the function specified by the user.